SARS-CoV-2 infection rates of antibody-positive compared with antibody-negative health-care workers in England: a large, multicentre, prospective cohort study (SIREN)

Prognostic value of anti-SARS-CoV-2 antibodies: a systematic review

OBJECTIVES

Globally, over 772 million cases of COVID-19 have been reported. New variants of interest with corresponding spikes in case numbers continue to be identified. Vulnerable patients, including older adults or patients with severe comorbidities, continue to be at risk. A large body of evidence has been accumulated regarding anti-SARS-CoV-2-antibodies and COVID-19 but the usefulness of antibody measurements remains unclear. This systematic review aims to assess the prognostic value of anti-SARS-CoV-2-antibodies and their usefulness for guiding booster vaccinations.

METHODS

Studies in English and published between January 2020 and October 2023 were included. Studies that relied on multiparameter-models or comprised fewer than 100 participants were excluded. PubMed and via the WHO COVID-19 research database, Embase and Medline databases were searched. Study selection and quality assessment was conducted independently by two researchers.

RESULTS

After screening 1,160 studies, 33 studies comprising >30 million individuals were included. Anti-SARS-CoV-2-antibodies were strongly associated with reduced risk of SARS-CoV-2-infection and better outcomes, including mortality. Risk of infection and COVID-19 severity decreased with increasing antibody levels.

CONCLUSIONS

Anti-SARS-CoV-2-antibodies are useful for early identification of high-risk patients and timely adjustment of therapy. Protective thresholds may be applied to advise booster vaccinations but verification in separate cohorts is required.

Estimating the incidence of COVID-19, influenza and respiratory syncytial virus infection in three regions of Queensland, Australia, winter 2022: findings from a novel longitudinal testing-based sentinel surveillance programme

OBJECTIVE

The 2022 Australian winter was the first time that COVID-19, influenza and respiratory syncytial virus (RSV) were circulating in the population together, after two winters of physical distancing, quarantine and borders closed to international travellers. We developed a novel surveillance system to estimate the incidence of COVID-19, influenza and RSV in three regions of Queensland, Australia.

DESIGN

We implemented a longitudinal testing-based sentinel surveillance programme. Participants were provided with self-collection nasal swabs to be dropped off at a safe location at their workplace each week. Swabs were tested for SARS-CoV-2 by PCR. Symptomatic participants attended COVID-19 respiratory clinics to be tested by multiplex PCR for SARS-CoV-2, influenza A and B and RSV. Rapid antigen test (RAT) results reported by participants were included in the analysis.

SETTING AND PARTICIPANTS

Between 4 April 2022 and 3 October 2022, 578 adults were recruited via their workplace. Due to rolling recruitment, withdrawals and completion due to positive COVID-19 results, the maximum number enrolled in any week was 423 people.

RESULTS

A total of 4290 tests were included. Participation rates varied across the period ranging from 25.9% to 72.1% of enrolled participants. The total positivity of COVID-19 was 3.3%, with few influenza or RSV cases detected. Widespread use of RAT may have resulted in few symptomatic participants attending respiratory clinics. The weekly positivity rate of SARS-CoV-2 detected during the programme correlated with the incidence of notified cases in the corresponding communities.

CONCLUSION

This testing-based surveillance programme could estimate disease trends and be a useful tool in settings where testing is less common or accessible. Difficulties with recruitment meant the study was underpowered. The frontline sentinel nature of workplaces meant participants were not representative of the general population but were high-risk groups providing early warning of disease.

A retrospective study suggests 55 days of persistence of SARS-CoV-2 during the first wave of the pandemic in Santiago de Chile

Background

As the COVID-19 pandemic persists, infections continue to surge globally. Presently, the most effective strategies to curb the disease and prevent outbreaks involve fostering immunity, promptly identifying positive cases, and ensuring their timely isolation. Notably, there are instances where the SARS-CoV-2 virus remains infectious even after patients have completed their quarantine.

Objective

Understanding viral persistence post-quarantine is crucial as it could account for localized infection outbreaks. Therefore, studying and documenting such instances is vital for shaping future public health policies.

Design

This study delves into a unique case of SARS-CoV-2 persistence in a 60-year-old female healthcare worker with a medical history of hypertension and hypothyroidism. The research spans 55 days, marking the duration between her initial and subsequent diagnosis during Chile's first COVID-19 wave, with the analysis conducted using RT-qPCR.

Results

Genomic sequencing-based phylogenetic analysis revealed that the SARS-CoV-2 detected in both Nasopharyngeal swab samples (NPSs) was consistent with the 20B clade of the Nextstrain classification, even after a 55-day interval.

Conclusion

This research underscores the need for heightened vigilance concerning cases of viral persistence. Such instances, albeit rare, might be pivotal in understanding sporadic infection outbreaks that occur post-quarantine.

Prediction of Prospective Mutational Landscape of SARS-CoV-2 Spike ssRNA and Evolutionary Basis of Its Host Interaction

Booster doses are crucial against severe COVID-19, as rapid virus mutations and variant emergence prolong the pandemic crisis. The virus's quick evolution, short generation-time, and adaptive changes impact virulence and evolvability, helping predictions about variant of concerns' (VOCs') landscapes. Here, in this study, we used a new computational algorithm, to predict the mutational pattern in SARS-CoV-2 ssRNA, proteomics, structural identification, mutation stability, and functional correlation, as well as immune escape mechanisms. Interestingly, the sequence diversity of SARS Coronavirus-2 has demonstrated a predominance of G- > A and C- > U substitutions. The best validation statistics are explored here in seven homologous models of the expected mutant SARS-CoV-2 spike ssRNA and employed for hACE2 and IgG interactions. The interactome profile of SARS-CoV-2 spike with hACE2 and IgG revealed a strong correlation between phylogeny and divergence time. The systematic adaptation of SARS-CoV-2 spike ssRNA influences infectivity and immune escape. Data suggest higher propensity of Adenine rich sequence promotes MHC system avoidance, preferred by A-rich codons. Phylogenetic data revealed the evolution of SARS-CoV-2 lineages' epidemiology. Our findings may unveil processes governing the genesis of immune-resistant variants, prompting a critical reassessment of the coronavirus mutation rate and exploration of hypotheses beyond mechanical aspects.

Post-vaccination SARS-CoV-2 IgG spike antibody responses among clinical and non-clinical healthcare workers at a tertiary facility in Kenya

INTRODUCTION

Following the coronavirus disease 19 (COVID-19), caused by severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) infection, vaccination became the main strategy against disease severity and even death. Healthcare workers were considered high-risk for infection and, thus, were prioritised for vaccination.

METHODS

A follow-up to a SARS-CoV-2 seroprevalence study among clinical and non-clinical HCWs at the Aga Khan University Hospital, Nairobi, we assessed how vaccination influenced SARS-CoV-2 anti-spike IgG antibody responses and kinetics. Blood samples were drawn at two points spanning 6 to 18 months post-vaccination, and SARS-CoV-2 spike antibody levels were determined by enzyme-linked immunosorbent assay.

RESULTS

Almost all participants, 98% (961/981), received a second vaccine dose, and only 8.5% (83/981) received a third dose. SARS-CoV-2 spike IgG antibodies were detected in 100% (961/961) and 92.7% (707/762) of participants who received two vaccine doses, with the first and second post-vaccine test, respectively, and in 100% (83/83) and 91.4% (64/70) of those who received three vaccine doses at the first and second post-vaccine test, respectively. Seventy-six participants developed mild infections, not requiring hospitalisation even after receiving primary vaccination. Receiving three vaccine doses influenced the anti-spike S/Co at both the first (p<0.001) and second post-vaccination testing (p<0.001). Of those who tested SARS-CoV-2 positive, the anti-spike S/Co ratio was significantly higher than those who were seronegative at the first post-vaccine test (p = 0.001). Side effects were reported by almost half of those who received the first dose, 47.3% (464/981), 28.9% (278/961) and 25.3% (21/83) of those who received the second and third vaccine doses, respectively.

DISCUSSION AND CONCLUSION

Following the second dose of primary vaccination, all participants had detectable anti-spike antibodies. The observed mild breakthrough infections may have been due to emerging SARS-CoV-2 variants. Findings suggest that although protective antibodies are induced, vaccination protected against COVID-19 disease severity and not necessarily infection.

Prevalence of neutralizing antibodies against SARS-CoV-2 using a rapid serological test in health workers of a Spanish Department of Health in Alicante (Spain) before the booster dose of the vaccine

AIM

To study the prevalence of neutralizing antibodies in healthcare workers and healthcare support personnel after the administration of the second dose of the BNT162b2 vaccine (Pfizer-BioNTech).

MATERIALS AND METHODS

In December 2021, we undertook a study in the Health Department in Orihuela, Alicante (Spain), which consists of 1500 workers. We collected demographic variables about the study participants, and we performed a "point-of-care" immunochromatography test to measure the presence of neutralizing antibodies (OJABIO® SARS-CoV-2 Neutralizing Antibody Detection Kit, manufactured by Wenzhou OJA Biotechnology Co., Ltd. Wenzhou, Zhejiang, China) before the administration of the third dose of the vaccine.

RESULTS

We obtained complete information about 964 (64%) workers, which consisted of 290 men and 674 women. The average age was 45,8 years (min. 18, max. 68) and the average time since the last dose of the vaccine was 40,5 weeks (min. 1,71, max. 47,71). A total of 131 participants (13,5%) had suffered infection by SARS-CoV-2 confirmed using RT-PCR. The proportion of participants who showed presence of neutralizing antibodies was 38,5%. In the multivariable analysis, the time since the last dose of the vaccine (aOR week: 1,07; 95%CI: 1,04; 1,09) and previous infection by SARS-CoV-2 (aOR: 3,7; 95CI: 2,39; 5,63) showed a statistically significant association with the presence of neutralizing antibodies.

CONCLUSIONS

The time since the administration of the last dose of the vaccine and the previous infection by SARS-CoV-2 determined the presence of neutralizing antibodies in 38,5% of the healthcare workers and support workers.

Increased antibody titers but induced T cell AICD and apoptosis response in COVID-19 convalescents by inactivated vaccine booster

It is urgently needed to evaluate the necessity and benefits of booster vaccination against the coronavirus 2 of the severe acute respiratory syndrome (SARS-CoV-2) Omicron to facilitate clinical decision-making for 2019 coronavirus disease (COVID-19) convalescents. We conducted a multicenter, prospective clinical trial (registration number: ChiCTR2100045810) in the first patients with COVID-19 from 28 January 2020 to 20 February 2020 to assess the long-term durability of neutralizing antibodies against live Omicron BA.5 and further assess the efficiency and safety of CoronaVac in the convalescent group. A total of 96 COVID-19 convalescents were enrolled in this study. Neutralizing antibody titers in convalescents were significantly reduced in 9-10 months. A dose-refreshing vaccination in 28 convalescents with an antibody titer below 96 significantly induced neutralizing antibodies against live Omicron by 4.84-fold. Meanwhile, the abundance of naive T cells increased dramatically, and TEMRA and TEM cells gradually decreased after vaccination. Activation-induced cell death and apoptosis-related genes were significantly elevated after vaccination in all T-cell subtypes. One-dose booster vaccination was effective in inducing a robust antibody response against SARS-CoV-2 Omicron in COVID-19 convalescents with low antibody titers. However, vaccine-mediated T-cell consumption and regeneration patterns may be detrimental to the antiviral response.IMPORTANCEThe globally dominant coronavirus 2 of the severe acute respiratory syndrome (SARS-CoV-2) Omicron variant raises the possibility of repeat infections among 2019 coronavirus disease (COVID-19) convalescents with low neutralizing antibody titers. The importance of this multicenter study lies in its evaluation of the long-term durability of neutralizing antibodies in COVID-19 convalescents and the efficacy of a booster vaccination against the live Omicron. The findings suggest that a one-dose booster vaccination is effective in inducing a robust antibody response against SARS-CoV-2 Omicron in convalescents with low antibody titers. However, the study also highlights the potential detrimental effects on the antiviral response due to vaccine-mediated T-cell consumption and regeneration patterns. These results are crucial for facilitating clinical decision-making for COVID-19 convalescents and informing public health policies regarding booster vaccinations.

Cross-protective HCoV immunity reduces symptom development during SARS-CoV-2 infection

Numerous clinical parameters link to severe coronavirus disease 2019, but factors that prevent symptomatic disease remain unknown. We investigated the impact of severe acute respiratory syndrome coronavirus type 2 (SARS-CoV-2) and endemic human coronavirus (HCoV) antibody responses on symptoms in a longitudinal children cohort (n = 2,917) and a cross-sectional cohort including children and adults (n = 882), all first exposed to SARS-CoV-2 (March 2020 to March 2021) in Switzerland. Saliva (n = 4,993) and plasma (n = 7,486) antibody reactivity to the four HCoVs (subunit S1 [S1]) and SARS-CoV-2 (S1, receptor binding domain, subunit S2 [S2], nucleocapsid protein) was determined along with neutralizing activity against SARS-CoV-2 Wuhan, Alpha, Delta, and Omicron (BA.2) in a subset of individuals. Inferred recent SARS-CoV-2 infection was associated with a strong correlation between mucosal and systemic SARS-CoV-2 anti-spike responses. Individuals with pre-existing HCoV-S1 reactivity exhibited significantly higher antibody responses to SARS-CoV-2 in both plasma (IgG regression coefficients = 0.20, 95% CI = [0.09, 0.32], P < 0.001) and saliva (IgG regression coefficient = 0.60, 95% CI = [0.088, 1.11], P = 0.025). Saliva neutralization activity was modest but surprisingly broad, retaining activity against Wuhan (median NT50 = 32.0, 1Q-3Q = [16.4, 50.2]), Alpha (median NT50 = 34.9, 1Q-3Q = [26.0, 46.6]), and Delta (median NT50 = 28.0, 1Q-3Q = [19.9, 41.7]). In line with a rapid mucosal defense triggered by cross-reactive HCoV immunity, asymptomatic individuals presented with higher pre-existing HCoV-S1 activity in plasma (IgG HKU1, odds ratio [OR] = 0.53, 95% CI = [0.29,0.97], P = 0.038) and saliva (total HCoV, OR = 0.55, 95% CI = [0.33, 0.91], P = 0.019) and higher SARS-CoV-2 reactivity in saliva (IgG S2 fold change = 1.26, 95% CI = [1.03, 1.54], P = 0.030). By investigating the systemic and mucosal immune responses to SARS-CoV-2 and HCoVs in a population without prior exposure to SARS-CoV-2 or vaccination, we identified specific antibody reactivities associated with lack of symptom development.IMPORTANCEKnowledge of the interplay between human coronavirus (HCoV) immunity and severe acute respiratory syndrome coronavirus type 2 (SARS-CoV-2) infection is critical to understanding the coexistence of current endemic coronaviruses and to building knowledge potential future zoonotic coronavirus transmissions. This study, which retrospectively analyzed a large cohort of individuals first exposed to SARS-CoV-2 in Switzerland in 2020-2021, revealed several key findings. Pre-existing HCoV immunity, particularly mucosal antibody responses, played a significant role in improving SARS-CoV-2 immune response upon infection and reducing symptoms development. Mucosal neutralizing activity against SARS-CoV-2, although low in magnitude, retained activity against SARS-CoV-2 variants underlining the importance of maintaining local mucosal immunity to SARS-CoV-2. While the cross-protective effect of HCoV immunity was not sufficient to block infection by SARS-CoV-2, the present study revealed a remarkable impact on limiting symptomatic disease. These findings support the feasibility of generating pan-protective coronavirus vaccines by inducing potent mucosal immune responses.

Silent battles: immune responses in asymptomatic SARS-CoV-2 infection

SARS-CoV-2 infections manifest with a broad spectrum of presentations, ranging from asymptomatic infections to severe pneumonia and fatal outcomes. This review centers on asymptomatic infections, a widely reported phenomenon that has substantially contributed to the rapid spread of the pandemic. In such asymptomatic infections, we focus on the role of innate, humoral, and cellular immunity. Notably, asymptomatic infections are characterized by an early and robust innate immune response, particularly a swift type 1 IFN reaction, alongside a rapid and broad induction of SARS-CoV-2-specific T cells. Often, antibody levels tend to be lower or undetectable after asymptomatic infections, suggesting that the rapid control of viral replication by innate and cellular responses might impede the full triggering of humoral immunity. Even if antibody levels are present in the early convalescent phase, they wane rapidly below serological detection limits, particularly following asymptomatic infection. Consequently, prevalence studies reliant solely on serological assays likely underestimate the extent of community exposure to the virus.

High diagnostic accuracy of quantitative SARS-CoV-2 spike-binding-IgG assay and correlation with in vitro viral neutralizing activity

Background

Antibody testing can easily evaluate the clinical status of patients, aid in the diagnosis of multisystem inflammatory syndrome, and monitor the immunity level in the population. However, the applicability of serological tests in detecting antibodies against the severe acute respiratory syndrome 2 (SARS-CoV-2) spike-binding protein remains limited. This study aimed to quantify both serum-derived neutralizing immunoglobulin-G (IgG) antibody activity and the amount of anti-SARS-CoV-2 Spike-IgG (S-IgG) in convalescent sera/plasmas and evaluate the direct correlation between the in vitro IgG-EC50 values and S-IgG values.

Methods

We evaluated the neutralizing activity of purified IgG (IgG-EC50), quantified S-IgG in the serum/plasma of consecutive COVID-19 convalescent individuals using a cell-based virus-neutralizing assay, and determined the correlation between IgG-EC50 and S-IgG. In addition, we evaluated rational cut-off values using the receiver operating characteristic (ROC) curve and calculated the sensitivity and specificity of the quantitative S-IgG assay for moderate and high IgG-EC50.

Results

A high correlation was observed between S-IgG and IgG-EC50 with a Spearman's ρ value of -0.748 (95 % confidence interval [CI]: -0.804-0.678). Using an IgG-EC50 of 50 μg/mL and 20 μg/mL as the cut-off values for moderate and high in vitro neutralizing activity, respectively, the Youden's index values of 287.5 binding antibody units (BAU)/mL and 454.1 BAU/mL determined from the ROC curve showed the highest diagnostic accuracy, with Kappa values of 0.884 (95 % CI: 0.823-0.946) and 0.920 (95 % CI: 0.681-0.979), respectively.

Conclusions

Quantitative S-IgG tests are a useful and convenient tool for estimating in vitro virus-neutralizing activity, with a high correlation with IgG-EC50 when the rational cut-off value is carefully determined.

Long-Term Kinetics of SARS-CoV-2 Neutralizing and Anti-Receptor Binding Domain Antibodies among Laboratory-Confirmed COVID-19 Cases in Delhi National Capital Region, India: A Prospective, One-Year Follow-Up Study

Background: This study was conducted with the objective of measuring the neutralizing and anti-receptor binding domain antibody levels against SARS-CoV-2 among laboratory-confirmed COVID-19 cases and exploring its long-term kinetics over a period of 1 year. Methods: One hundred laboratory-confirmed COVID-19 cases were recruited. Serum samples of the participants were collected within three months from the date of the positive COVID-19 report. The participants were prospectively followed up every three months for symptoms and the collection of blood samples for three additional rounds. The presence of anti-SARS-CoV-2 antibodies (IgA, IgG, and IgM antibodies), anti-receptor binding domain antibodies (anti-RBD), and neutralizing antibodies were measured. Findings: Median plaque reduction neutralization test (PRNT) titers showed a rising trend in the first three rounds of follow-up. The quantitative anti-receptor binding domain ELISA (QRBD) values showed a declining trend in the initial three rounds. However, both the PRNT titers and QRBD values showed significantly higher values for the fourth round of follow-up. Total antibody (WANTAI) levels showed an increasing trend in the initial three rounds (statistically significant). Interpretation: Neutralizing antibodies showed an increasing trend. The anti-receptor binding domain antibodies showed a decreasing trend. Neutralizing antibodies and anti-RBD antibodies persisted in the majority.

Humoral and Cellular Immune Response after Three Doses of Sinopharm [Vero Cell]-Inactivated COVID-19 Vaccine in Combination with SARS-CoV-2 Infection Leads to Hybrid Immunity

BACKGROUND

Several vaccines against COVID-19 have been developed and licensed to enhance the immune response against SARS-CoV-2. Similarly, previous infection with SARS-CoV-2 has been shown to provide significant protection against severe infection and hospitalization.

METHODS

We investigated the effect of three doses of the Sinopharm vaccine and SARS-CoV-2 infection on the specific immune response in 103 volunteers, measuring neutralizing antibodies, anti-S1 IgG, anti-RBD IgM, anti-N IgM, anti-N IgG antibodies, and INF γ.

RESULTS

Our results showed that the presence of cardiovascular diseases increased the level of anti-N-IgG antibodies, while endocrinological diseases decreased the level of neutralizing antibodies and anti-N IgG antibodies, suggesting that these diseases alter the effect of vaccine-induced immunity. In addition, there was a significant decrease in anti-S1 IgG levels at 6 months and in anti-N IgG levels 18 months post-infection, while neutralizing antibodies and INF γ levels were constant at 3, 6, and 18 months post-infection.

CONCLUSIONS

Our results confirm the emergence of hybrid immunity, which is the strongest and most durable compared to natural immunity or vaccine-induced immunity. Significant positive correlations were found between humoral and cellular immunity markers: neutralizing antibodies, anti-S1 IgG and anti-N IgG antibodies, and INF γ, indicating a unique coordinated response specific to COVID-19.

The effectiveness and efficiency of asymptomatic SARS-CoV-2 testing strategies for patient and healthcare workers within acute NHS hospitals during an omicron-like period

BACKGROUND

Asymptomatic SARS-CoV-2 testing of hospitalised patients began in April-2020, with twice weekly healthcare worker (HCW) testing introduced in November-2020. Guidance recommending asymptomatic testing was withdrawn in August-2022. Assessing the impact of this decision from data alone is challenging due to concurrent changes in infection prevention and control practices, community transmission rates, and a reduction in ascertainment rate from reduced testing. Computational modelling is an effective tool for estimating the impact of this change.

METHODS

Using a computational model of SARS-CoV-2 transmission in an English hospital we estimate the effectiveness of several asymptomatic testing strategies, namely; (1) Symptomatic testing of patients and HCWs, (2) testing of all patients on admission with/without repeat testing on days 3 and 5-7, and (3) symptomatic testing plus twice weekly asymptomatic HCW testing with 70% compliance. We estimate the number of patient and HCW infections, HCW absences, number of tests, and tests per case averted or absence avoided, with differing community prevalence rates over a 12-week period.

RESULTS

Testing asymptomatic patients on admission reduces the rate of nosocomial SARS-CoV-2 infection by 8.1-21.5%. Additional testing at days 3 and 5-7 post admission does not significantly reduce infection rates. Twice weekly asymptomatic HCW testing can reduce the proportion of HCWs infected by 1.0-4.4% and monthly absences by 0.4-0.8%. Testing asymptomatic patients repeatedly requires up to 5.5 million patient tests over the period, and twice weekly asymptomatic HCW testing increases the total tests to almost 30 million. The most efficient patient testing strategy (in terms of tests required to prevent a single patient infection) was testing asymptomatic patients on admission across all prevalence levels. The least efficient was repeated testing of patients with twice weekly asymptomatic HCW testing in a low prevalence scenario, and in all other prevalence levels symptomatic patient testing with regular HCW testing was least efficient.

CONCLUSIONS

Testing patients on admission can reduce the rate of nosocomial SARS-CoV-2 infection but there is little benefit of additional post-admission testing. Asymptomatic HCW testing has little incremental benefit for reducing patient cases at low prevalence but has a potential role at higher prevalence or with low community transmission. A full health-economic evaluation is required to determine the cost-effectiveness of these strategies.

COVID-19 mRNA Vaccines: Lessons Learned from the Registrational Trials and Global Vaccination Campaign

Our understanding of COVID-19 vaccinations and their impact on health and mortality has evolved substantially since the first vaccine rollouts. Published reports from the original randomized phase 3 trials concluded that the COVID-19 mRNA vaccines could greatly reduce COVID-19 symptoms. In the interim, problems with the methods, execution, and reporting of these pivotal trials have emerged. Re-analysis of the Pfizer trial data identified statistically significant increases in serious adverse events (SAEs) in the vaccine group. Numerous SAEs were identified following the Emergency Use Authorization (EUA), including death, cancer, cardiac events, and various autoimmune, hematological, reproductive, and neurological disorders. Furthermore, these products never underwent adequate safety and toxicological testing in accordance with previously established scientific standards. Among the other major topics addressed in this narrative review are the published analyses of serious harms to humans, quality control issues and process-related impurities, mechanisms underlying adverse events (AEs), the immunologic basis for vaccine inefficacy, and concerning mortality trends based on the registrational trial data. The risk-benefit imbalance substantiated by the evidence to date contraindicates further booster injections and suggests that, at a minimum, the mRNA injections should be removed from the childhood immunization program until proper safety and toxicological studies are conducted. Federal agency approval of the COVID-19 mRNA vaccines on a blanket-coverage population-wide basis had no support from an honest assessment of all relevant registrational data and commensurate consideration of risks versus benefits. Given the extensive, well-documented SAEs and unacceptably high harm-to-reward ratio, we urge governments to endorse a global moratorium on the modified mRNA products until all relevant questions pertaining to causality, residual DNA, and aberrant protein production are answered.

Immunogenicity of BNT162b2 vaccine after two and three doses in health personnel and institutionalized elderly people not infected with SARS-CoV-2

OBJECTIVE

The aim of our research was to compare the evolution of the immune response induced by the BNT162b2 vaccine after the administration of two and three doses in healthcare personnel and in institutionalized elderly people (>65 years of age) without previous SARS-CoV-2 infection.

MATERIAL AND METHODS

A prospective observational study was carried out on a convenience sample made up of health workers and institutionalized elderly people, measuring antibodies against S and N proteins of SARS-CoV-2 two and six months after receiving the second vaccine dose, as well as two months after receiving the third dose.

RESULTS

A significant reduction of the anti-S humoral immune response was reported six months after the second dose of vaccine in both health workers and residents. The administration of a third dose of vaccine induced a significant increase in this antibody response in both investigated groups reaching a similar proportion of responders two months after this third dose.

CONCLUSIONS

Humoral immunity induced by two doses of the BNT162b2 vaccine in persons without prior SARS-CoV-2 infection wanes over time. The administration of a third dose significantly increases anti-S antibodies being highly recommended, especially in people over 65 years of age.

Exploring the potential of learning methods and recurrent dynamic model with vaccination: A comparative case study of COVID-19 in Austria, Brazil, and China

In order to effectively manage infectious diseases, it is crucial to understand the interplay between disease dynamics and human conduct. Various factors can impact the control of an epidemic, including social interventions, adherence to health protocols, mask-wearing, and vaccination. This article presents the development of an innovative hybrid model, known as the Combined Dynamic-Learning Model, that integrates classical recurrent dynamic models with four different learning methods. The model is composed of two approaches: The first approach introduces a traditional dynamic model that focuses on analyzing the impact of vaccination on the occurrence of an epidemic, and the second approach employs various learning methods to forecast the potential outcomes of an epidemic. Furthermore, our numerical results offer an interesting comparison between the traditional approach and modern learning techniques. Our classic dynamic model is a compartmental model that aims to analyze and forecast the diffusion of epidemics. The model we propose has a recurrent structure with piecewise constant parameters and includes compartments for susceptible, exposed, vaccinated, infected, and recovered individuals. This model can accurately mirror the dynamics of infectious diseases, which enables us to evaluate the impact of restrictive measures on the spread of diseases. We conduct a comprehensive dynamic analysis of our model. Additionally, we suggest an optimal numerical design to determine the parameters of the system. Also, we use regression tree learning, bidirectional long short-term memory, gated recurrent unit, and a combined deep learning method for training and evaluation of an epidemic. In the final section of our paper, we apply these methods to recently published data on COVID-19 in Austria, Brazil, and China from 26 February 2021 to 4 August 2021, which is when vaccination efforts began. To evaluate the numerical results, we utilized various metrics such as RMSE and R-squared. Our findings suggest that the dynamic model is ideal for long-term analysis, data fitting, and identifying parameters that impact epidemics. However, it is not as effective as the supervised learning method for making long-term forecasts. On the other hand, supervised learning techniques, compared to dynamic models, are more effective for predicting the spread of diseases, but not for analyzing the behavior of epidemics.

Association between severe acute respiratory syndrome coronavirus 2 antibody status and reinfection: A case-control study nested in a Colorado-based prospective cohort study

The association between the presence of detectable antibodies to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and SARS-CoV-2 reinfection is not well established. The objective of this study was to determine the association between antibody seronegativity and reinfection.

METHODS

Participants in Colorado, USA, were recruited between June 15, 2020, and March 28, 2021, and encouraged to complete SARS-CoV-2 molecular ribonucleic acid (RNA) and serology testing for antibodies every 28 days for 10 months. Participants with reinfections (positive SARS-CoV-2 RNA test ≥ 90 days after the first positive RNA test) were matched to controls without reinfections by age, sex, date of the first positive RNA test, date of the last serology test, and serology test type. Using conditional logistic regression, case patients were compared to control patients on the last serologic test result, with adjustment for demographic and clinical confounders.

RESULTS

The cohort (n = 4,235) included 2,033 participants with ≥ 1 positive RNA test, of whom 120 had reinfection. Among the 80 case patients who could be matched, the last serologic test was negative in 12 of the cases (15.0 %) whereas the last serologic test was negative in 77 of 1,034 (7.5 %) controls. Seronegativity (adjusted OR [aOR] 2.24; 95 % CI 1.07, 4.68), Hispanic ethnicity (aOR 1.87; 95 % 1.10, 3.18), and larger household size (aOR 1.15; 95 % 1.01, 1.30 for each additional household member) were associated with reinfection.

CONCLUSIONS

Seronegative status, Hispanic ethnicity, and increasing household size were associated with reinfection. Serologic testing could be considered to reduce vaccine hesitancy in higher risk populations.

Clinical and laboratory considerations: determining an antibody-based composite correlate of risk for reinfection with SARS-CoV-2 or severe COVID-19

Much of the global population now has some level of adaptive immunity to SARS-CoV-2 induced by exposure to the virus (natural infection), vaccination, or a combination of both (hybrid immunity). Key questions that subsequently arise relate to the duration and the level of protection an individual might expect based on their infection and vaccination history. A multi-component composite correlate of risk (CoR) could inform individuals and stakeholders about protection and aid decision making. This perspective evaluates the various elements that need to be accommodated in the development of an antibody-based composite CoR for reinfection with SARS-CoV-2 or development of severe COVID-19, including variation in exposure dose, transmission route, viral genetic variation, patient factors, and vaccination status. We provide an overview of antibody dynamics to aid exploration of the specifics of SARS-CoV-2 antibody testing. We further discuss anti-SARS-CoV-2 immunoassays, sample matrices, testing formats, frequency of sampling and the optimal time point for such sampling. While the development of a composite CoR is challenging, we provide our recommendations for each of these key areas and highlight areas that require further work to be undertaken.

Predictors of Breakthrough SARS-CoV-2 Infection after Vaccination

The initial two-dose vaccine series and subsequent booster vaccine doses have been effective in modulating SARS-CoV-2 disease severity and death but do not completely prevent infection. The correlates of infection despite vaccination continue to be under investigation. In this prospective decentralized study (n = 1286) comparing antibody responses in an older- (≥70 years) to a younger-aged cohort (aged 30-50 years), we explored the correlates of breakthrough infection in 983 eligible subjects. Participants self-reported data on initial vaccine series, subsequent booster doses and COVID-19 infections in an online portal and provided self-collected dried blood spots for antibody testing by ELISA. Multivariable survival analysis explored the correlates of breakthrough infection. An association between higher antibody levels and protection from breakthrough infection observed during the Delta and Omicron BA.1/2 waves of infection no longer existed during the Omicron BA.4/5 wave. The older-aged cohort was less likely to have a breakthrough infection at all time-points. Receipt of an original/Omicron vaccine and the presence of hybrid immunity were associated with protection of infection during the later Omicron BA.4/5 and XBB waves. We were unable to determine a threshold antibody to define protection from infection or to guide vaccine booster schedules.

Evaluating pooled testing for asymptomatic screening of healthcare workers in hospitals

BACKGROUND

There is evidence that during the COVID pandemic, a number of patient and HCW infections were nosocomial. Various measures were put in place to try to reduce these infections including developing asymptomatic PCR (polymerase chain reaction) testing schemes for healthcare workers. Regularly testing all healthcare workers requires many tests while reducing this number by only testing some healthcare workers can result in undetected cases. An efficient way to test as many individuals as possible with a limited testing capacity is to consider pooling multiple samples to be analysed with a single test (known as pooled testing).

METHODS

Two different pooled testing schemes for the asymptomatic testing are evaluated using an individual-based model representing the transmission of SARS-CoV-2 in a 'typical' English hospital. We adapt the modelling to reflect two scenarios: a) a retrospective look at earlier SARS-CoV-2 variants under lockdown or social restrictions, and b) transitioning back to 'normal life' without lockdown and with the omicron variant. The two pooled testing schemes analysed differ in the population that is eligible for testing. In the 'ward' testing scheme only healthcare workers who work on a single ward are eligible and in the 'full' testing scheme all healthcare workers are eligible including those that move across wards. Both pooled schemes are compared against the baseline scheme which tests only symptomatic healthcare workers.

RESULTS

Including a pooled asymptomatic testing scheme is found to have a modest (albeit statistically significant) effect, reducing the total number of nosocomial healthcare worker infections by about 2[Formula: see text] in both the lockdown and non-lockdown setting. However, this reduction must be balanced with the increase in cost and healthcare worker isolations. Both ward and full testing reduce HCW infections similarly but the cost for ward testing is much less. We also consider the use of lateral flow devices (LFDs) for follow-up testing. Considering LFDs reduces cost and time but LFDs have a different error profile to PCR tests.

CONCLUSIONS

Whether a PCR-only or PCR and LFD ward testing scheme is chosen depends on the metrics of most interest to policy makers, the virus prevalence and whether there is a lockdown.

Anti-SARS-CoV-2 Antibody Testing: Role and Indications

Since the onset of the COVID-19 pandemic in March 2020, over 769 million confirmed COVID-19 cases, including close to 7 million COVID-19-related deaths, have been reported. Although mortality rates have dropped notably compared to the first months of the pandemic, spikes in reported cases and mortality rates continue to be registered. Both recent spikes in case numbers and the continued emergence of new variants suggest that vulnerable patient groups, including older adults, immunocompromised patients, and patients with severe comorbidities, are going to continue to be affected by COVID-19. In order to curb the pandemic, relieve the pressure on primary care facilities, and reduce mortality rates, global vaccination programs have been established by the WHO, with over 13.5 billion vaccine doses having been administered globally. In most immunocompetent individuals, vaccination against COVID-19 results in the production of anti-SARS-CoV-2 spike antibodies. However, certain patient subsets have inadequate or reduced immune responses, and immune responses are known to decrease with age. General recommendations on the timing of booster vaccinations may therefore be insufficient to protect vulnerable patients. This review aims to evaluate the clinical role of anti-SARS-CoV-2 antibodies, focusing on measurement indications, prognostic value, and potential as a correlate of protection to guide future booster vaccination strategies.

SARS-CoV-2 reinfections in the pediatric cohort-a single-center experience

BACKGROUND

This study focused on timelines of infection episodes and dominant variants and aims to determine disease severity and outcome of pediatric patients with reinfection.

MATERIALS AND METHODS

This study retrospectively evaluated the medical records of the hospitalized patients and/or outpatients aged 0-18 with a positive severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) polymerase chain reaction between March 2020 and September 2022 at Ege University Children's Hospital.

RESULTS

Ninety-one pediatric patients reinfected with SARS-CoV-2 were included in the study. There was an underlying disease in 26.4% of the patients. The median time between the two infection episodes was 184 (90-662) days. There were 24 patients (26.3%) with the first infection in pre-Delta period; 17 (18.6%) of them were reinfected in Omicron BA.1 period, while 7 (7.6%) in Omicron BA.4/BA.5 period. Forty-five patients (49.4%) were infected initially in the Delta period; 35 patients (38.4%) were reinfected in the Omicron BA.1 period, while 10 patients (10.9%) were reinfected in the Omicron BA.4/BA.5 period. Twenty-two patients (24.1%) had the first infection in the Omicron BA.1 period and then reinfected in the Omicron BA.4/BA.5 period. Patients with reinfection more frequently displayed a symptom (84.6% vs. 94.5%, p = 0.03). The hospitalization rate significantly declined in reinfection (15.3% vs. 7.6%, p = 0.03). Severe disease, treatment needs and steroid use were decreased in reinfections without a significant difference (p > 0.05). Intensive care unit admission was not altered.

CONCLUSION

This study revealed that reinfections frequently develop in previously healthy children but do not cause more severe outcomes. The risk of symptomatic reinfections is still high due to the effect of the Omicron variant.

Persistence of SARS-CoV-2-antibodies against N, S and RBD after natural infection

Background and Objectives

Coronavirus disease 2019 (COVID-19) pandemic has affected most countries in the world. Monitoring the humoral immune responses during the natural course of Severe Acute Respiratory Syndrome Coronavirus-2 (SARS-CoV-2) infection and the duration of them provide useful information for the development of vaccination strategies against this virus and its emerging variants. The importance of the antibody response especially neutralizing antibodies in long-term immunity to SARS-CoV-2 is significant.

Materials and Methods

The present study is a cross-sectional study of sero-epidemiological type that has been proposed to compare the persistence of Immunoglobulin G (IgG) against N (nucleocapsid), S (spike) and RBD (receptor-binding domain) proteins in the community after the time of primary disease. A total of 652 serum samples were collected from hospital staff working in COVID wards, as well as a number of community members with different occupations, among those with positive antibody titers, 86 participated in the resampling test before vaccination.

Results

There was no association between antibody titer and disease severity (p>0.05). A significant decrease in Ab levels was observed in the paired second samples. The highest rate of decrease was related to anti-N, then anti-RBD and anti-S IgG levels, respectively. There is a significant relationship between the initial antibody titer and its reduction over time (p-value <0.05).

Conclusion

Our data revealed that humoral immunity following natural infection of SARS-CoV-2 is detectable for at least 4 months, regardless of disease severity. The most decrease in antibody titer over time was related to anti-N IgG levels.

Duplex Electrochemical Microfluidic Sensor for COVID-19 Antibody Detection: Natural versus Vaccine-Induced Humoral Response

The rapid transmission and resilience of coronavirus disease 2019 (COVID-19) have led to urgent demands in monitoring humoral response for effective vaccine development, thus a multiplex co-detection platform to discriminate infection-induced from vaccine-induced antibodies is needed. Here a duplex electrochemical immunosensor for co-detection of anti-nucleocapsid IgG (N-IgG) and anti-spike IgG (S-IgG) is developed by using a two-working electrode system, via an indirect immunoassay, with antibody quantification obtained by differential pulse voltammetry. The screen-printed electrodes (SPEs) are modified by carbon black and electrodeposited gold nanoflowers for maximized surface areas, enabling the construction of an immunological chain for S-IgG and N-IgG electrochemical detection with enhanced performance. Using an optimized immunoassay protocol, a wide linear range between 30-750 and 20-1000 ng mL-1 , and a limit of detection of 28 and 15 ng mL-1 are achieved to detect N-IgG and S-IgG simultaneously in serum samples. This duplex immunosensor is then integrated in a microfluidic device to obtain significantly reduced detection time (≤ 7 min) while maintaining its analytical performance. The duplex microfluidic immunosensor can be easily expanded into multiplex format to achieve high throughput screening for the sero-surveillance of COVID-19  and other infectious diseases.

Neutralizing Antibodies against SARS-CoV-2: Importance of Comorbidities in Health Personnel against Reinfections

One of the priority lines of action to contain the SARS-CoV-2 pandemic was vaccination programs for healthcare workers. However, with the emergence of highly contagious strains, such as the Omicron variant, it was necessary to know the serological status of health personnel to make decisions for the application of reinforcements. The aim of this work was to determine the seroprevalence against SARS-CoV-2 in healthcare workers in a Mexican hospital after six months of the administration of the Pfizer-BioNTech vaccine (two doses, 4 weeks apart) and to investigate the association between comorbidities, response to the vaccine, and reinfections. Neutralizing antibodies against SARS-CoV-2 were determined using ELISA assays for 262 employees of Hospital Juárez de México with and without a history of COVID-19. A beta regression analysis was performed to study the associated comorbidities and their relationship with the levels of antibodies against SARS-CoV-2. Finally, an epidemiological follow-up was carried out to detect reinfections in this population. A significant difference in SARS-CoV-2 seroprevalence was observed in workers with a history of COVID-19 prior to vaccination compared to those without a history of the disease (MD: 0.961 and SD: 0.049; <0.001). Beta regression showed that workers with a history of COVID-19 have greater protection compared to those without a history of the infection. Neutralizing antibodies were found to be decreased in alcoholic and diabetic subjects (80.1%). Notably, eight cases of Omicron reinfections were identified, and gender and obesity were associated with the presence of reinfections (6.41 OR; 95% BCa CI: 1.15, 105.0). The response to the vaccine was influenced by the history of SARS-CoV-2 infection and associated comorbidities. The above highlights the importance of prioritizing this segment of the population for reinforcements in periods of less than one year to guarantee their effectiveness against new variants.

The impact of SARS-CoV-2 on healthcare workers of a large University Hospital in the Veneto Region: risk of infection and clinical presentation in relation to different pandemic phases and some relevant determinants

Aim

The aim of this study is to evaluate the incidence of SARS-CoV-2 infection and the prevalence of COVID-19-related symptoms in relation to pandemic phases and some relevant variables in a cohort of 8,029 HCWs from one of the largest Italian University Hospitals.

Methods

A single-center retrospective study was performed on data collected during SARS-CoV-2 infection surveillance of HCWs. Cox's multiple regression was performed to estimate hazard ratios of SARS-CoV-2 infection. Logistic multivariate regression was used to assess the risk of asymptomatic infections and the onset of the most frequent symptoms. All analyses were adjusted for sociodemographic and occupational factors, pandemic phases, vaccination status, and previous infections.

Results

A total of 3,760 HCWs resulted positive (2.0%-18.6% across five study phases). The total incidence rate of SARS-CoV-2 infection was 7.31 cases per 10,000 person-days, significantly lower in phase 1 and higher in phases 4 and 5, compared to phase 3. Younger HCWs, healthcare personnel, and unvaccinated subjects showed a higher risk of infection. Overall, 24.5% were asymptomatic infections, with a higher probability for men, physicians, and HCWs tested for screening, fully vaccinated, and those with previous infection. The clinical presentation changed over the phases in relation to vaccination status and the emergence of new variants.

Conclusion

The screening activities of HCWs allowed for the early detection of asymptomatic cases, limiting the epidemic clusters inside the hospital wards. SARS-CoV-2 vaccination reduced infections and symptomatic cases, demonstrating again its paramount value as a preventive tool for occupational and public health.

Incidence and outcome of SARS-CoV-2 reinfection in the pre-Omicron era: A global systematic review and meta-analysis

Background

With the emergence of new variants and sub-lineages of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), reinfections can significantly impact herd immunity, vaccination policies, and decisions on other public health measures. We conducted a systematic review and meta-analysis to synthesise the global evidence on SARS-CoV-2 reinfections in the pre-Omicron era.

Methods

We searched five global databases (MEDLINE, Embase, CINAHL Plus, Global Health, WHO COVID-19) on 12 May 2022 and 28 July 2023 and three Chinese databases (CNKI, Wanfang, CQvip) on 16 October 2022 for articles reporting incidence and outcomes of SARS-CoV-2 reinfection before the period of Omicron (B.1.1.529) predominance. We assessed risk of bias using Joanna Briggs Institute critical appraisal tools and conducted meta-analyses with random effects models to estimate the proportion of SARS-CoV-2 reinfection among initially infected cases and hospitalisation and mortality proportions among reinfected ones.

Results

We identified 7593 studies and extracted data from 64 included ones representing 21 countries. The proportion of SARS-CoV-2 reinfection was 1.16% (95% confidence interval (CI) = 1.01-1.33) based on 11 639 247 initially infected cases, with ≥45 days between the two infections. Healthcare providers (2.28%; 95% CI = 1.37-3.40) had a significantly higher risk of reinfection than the general population (1.00%; 95% CI = 0.81-1.20), while young adults aged 18 to 35 years (1.01%; 95% CI = 0.8-1.25) had a higher reinfection burden than other age groups (children <18 years old: 0.57%; 95% CI = 0.39-0.79, older adults aged 36-65 years old: 0.53%; 95% CI = 0.41-0.65, elderly >65 years old: 0.37%; 95% CI = 0.15-0.66). Among the reinfected cases, 8.12% (95% CI = 5.30-11.39) were hospitalised, 1.31% (95% CI = 0.29-2.83) were admitted to the intensive care unit, and 0.71% (95% CI = 0.02-2.01) died.

Conclusions

Our data suggest a relatively low risk of SARS-CoV-2 reinfection in the pre-Omicron era, but the risk of hospitalisation was relatively high among the reinfected cases. Considering the possibility of underdiagnosis, the reinfection burden may be underestimated.

Registration

PROSPERO: CRD42023449712.

Unlocking the potential of RNA-based therapeutics in the lung: current status and future directions

Awareness of RNA-based therapies has increased after the widespread adoption of mRNA vaccines against SARS-CoV-2 during the COVID-19 pandemic. These mRNA vaccines had a significant impact on reducing lung disease and mortality. They highlighted the potential for rapid development of RNA-based therapies and advances in nanoparticle delivery systems. Along with the rapid advancement in RNA biology, including the description of noncoding RNAs as major products of the genome, this success presents an opportunity to highlight the potential of RNA as a therapeutic modality. Here, we review the expanding compendium of RNA-based therapies, their mechanisms of action and examples of application in the lung. The airways provide a convenient conduit for drug delivery to the lungs with decreased systemic exposure. This review will also describe other delivery methods, including local delivery to the pleura and delivery vehicles that can target the lung after systemic administration, each providing access options that are advantageous for a specific application. We present clinical trials of RNA-based therapy in lung disease and potential areas for future directions. This review aims to provide an overview that will bring together researchers and clinicians to advance this burgeoning field.

Predictors of COVID-19 vaccine uptake among persons aged 18 years and above in Ga North Municipality, Ghana using the Health Belief Model: A community-based cross-sectional study

BACKGROUND

Although the coronavirus disease 2019 (COVID-19) vaccination rollout has been accepted by the population of the Ga North Municipality, a substantial proportion has developed hesitancy to COVID-19 vaccination uptake. This study determined the predictors of COVID-19 vaccine uptake among persons aged 18 years and above in the Ga North Municipality using the Health Belief Model.

METHODS

The study used a cross-sectional study design. Structured questionnaires were used to collect data from a multistage sample of 388 respondents. Multivariable binary logistic regression was used to determine the predictors of COVID-19 vaccination uptake at the level of 0.05 and 95% confidence interval.

RESULTS

Vaccination uptake was 72.2%. The odds of COVID-19 vaccination uptake were higher among men than women [AOR = 2.02, 95% Cl: 1.13-3.20] and among singles than the married [AOR = 1.90, 95% Cl: 1.07-3.36], but lower among Muslims than Christians [AOR = 0.33, 95%Cl: 0.18-0.60]. Perceived susceptibility [AOR = 2.43, 95% Cl: 1.36-4.35], perceived barriers [AOR = 0.54, 95%Cl: 0.31-0.95], cues to action [AOR = 2.23, 95% Cl: 1.19-4.21] and self-efficacy [AOR = 3.23 95% Cl: 1.82-5.71] were the significant predictors of COVID-19 vaccination uptake.

CONCLUSION

The uptake of the COVID-19 vaccine in GA North Municipality is high. Health promotion interventions should focus on increasing perceived susceptibility to COVID-19, minimising barriers to COVID-19 vaccine uptake, and promoting cues and self-confidence for COVID-19 vaccine uptake. It should also target women, the married, and Muslims.

Seroprevalence and factors associated with SARS-CoV-2 infection among healthcare workers: cross-sectional study

BACKGROUND

Healthcare workers (HCWs) are at a higher risk of contracting COVID-19 due to their close contact with infected patients. However, the true burden of COVID-19 among HCWs in Yemen is unknown due to the inadequate availability of healthcare and the subclinical nature of the disease. This study aims to estimate the seroprevalence of SARS-CoV-2 infection among HCWs in two Yemeni governorates and identify associated factors using a cross-sectional design.

METHOD

A total of 404 HCWs were surveyed from June 2022 to September 2022 in Lahj and AL-Dhalea hospitals. A self-administered questionnaire collected demographic data, COVID-19 infection history, and vaccination status. A total of 404 human sera were tested using a specific electrochemiluminescence immunoassay assay. Association analysis was conducted to identify associations between antibody prevalence and demographic and vaccine-related variables.

RESULT

The median age of the HCWs was 31 (Range 20-64) years, with 65.0% being male and 35.0% female. Of all HCWs, 94% were SARS-CoV-2 seropositive and 77.0% had no confirmed test of COVID-19-related symptoms. There was no significant association between seropositivity and demographic factors such as age, gender, occupation, or COVID-19 vaccination (P > 0.05).

CONCLUSION

The seroprevalence of SARS-CoV-2 was high among HCWs in Yemen, primarily due to natural infection rather than vaccination. Compliance with infection prevention and control measures did not significantly affect seropositivity. This study highlights the need for improved healthcare systems and resources to reduce the burden of COVID-19 and promote infection prevention and control (IPC) measures among HCWs in Yemen.

The burden and dynamics of hospital-acquired SARS-CoV-2 in England

Hospital-based transmission had a dominant role in Middle East respiratory syndrome coronavirus (MERS-CoV) and severe acute respiratory syndrome coronavirus (SARS-CoV) epidemics1,2, but large-scale studies of its role in the SARS-CoV-2 pandemic are lacking. Such transmission risks spreading the virus to the most vulnerable individuals and can have wider-scale impacts through hospital-community interactions. Using data from acute hospitals in England, we quantify within-hospital transmission, evaluate likely pathways of spread and factors associated with heightened transmission risk, and explore the wider dynamical consequences. We estimate that between June 2020 and March 2021 between 95,000 and 167,000 inpatients acquired SARS-CoV-2 in hospitals (1% to 2% of all hospital admissions in this period). Analysis of time series data provided evidence that patients who themselves acquired SARS-CoV-2 infection in hospital were the main sources of transmission to other patients. Increased transmission to inpatients was associated with hospitals having fewer single rooms and lower heated volume per bed. Moreover, we show that reducing hospital transmission could substantially enhance the efficiency of punctuated lockdown measures in suppressing community transmission. These findings reveal the previously unrecognized scale of hospital transmission, have direct implications for targeting of hospital control measures and highlight the need to design hospitals better equipped to limit the transmission of future high-consequence pathogens.

SARS-CoV-2 Reinfection Risk in Persons with HIV, Chicago, Illinois, USA, 2020-2022

Understanding if persons with HIV (PWH) have a higher risk for SARS-CoV-2 reinfection may help tailor future COVID-19 public health guidance. To determine whether HIV infection was associated with increased risk for SARS-CoV-2 reinfection, we followed adult residents of Chicago, Illinois, USA, with SARS-CoV-2 longitudinally from their first reported infection through May 31, 2022. We matched SARS-CoV-2 laboratory data and COVID-19 vaccine administration data to Chicago's Enhanced HIV/AIDS Reporting System. Among 453,587 Chicago residents with SARS-CoV-2, a total of 5% experienced a SARS-CoV-2 reinfection, including 192/2,886 (7%) PWH and 23,642/450,701 (5%) persons without HIV. We observed higher SARS-CoV-2 reinfection incidence rates among PWH (66 [95% CI 57-77] cases/1,000 person-years) than PWOH (50 [95% CI 49-51] cases/1,000 person-years). PWH had a higher adjusted rate of SARS-CoV-2 reinfection (1.46, 95% CI 1.27-1.68) than those without HIV. PWH should follow the recommended COVID-19 vaccine schedule, including booster doses.

CD4+ and CD8+ T cells and antibodies are associated with protection against Delta vaccine breakthrough infection: a nested case-control study within the PITCH study

IMPORTANCE

Defining correlates of protection against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccine breakthrough infection informs vaccine policy for booster doses and future vaccine designs. Existing studies demonstrate humoral correlates of protection, but the role of T cells in protection is still unclear. In this study, we explore antibody and T cell immune responses associated with protection against Delta variant vaccine breakthrough infection in a well-characterized cohort of UK Healthcare Workers (HCWs). We demonstrate evidence to support a role for CD4+ and CD8+ T cells as well as antibodies against Delta vaccine breakthrough infection. In addition, our results suggest a potential role for cross-reactive T cells in vaccine breakthrough.

Demonstrating the learning and impact of embedding participant involvement in a pandemic research study: the experience of the SARS-CoV-2 immunity & reinfection evaluation (SIREN) study UK, 2020-2023

BACKGROUND

Participant involvement in research studies is not a new concept, yet barriers to implementation remain and application varies. This is particularly true for pandemic response research studies, where timeframes are condensed, pressure is high and the value and inclusion of participant involvement can be overlooked. The SIREN Participant Involvement Panel (PIP) provides a case study for participant involvement in pandemic research, working in partnership with people who the research is for and about.

METHODS

SIREN and the British Society for Immunology (BSI) recruited and ran two phases of the PIP, involving 15 members in total over a 16-month period. Phase 1 ran between January and August 2022 and Phase 2 between October 2022 and March 2023. Activity figures including recruitment interest and PIP meeting attendance were recorded. To evaluate how the PIP has influenced SIREN, feedback was collected from (a) researchers presenting at the PIP and (b) PIP members themselves. Evaluation at the end of Phase 1 informed our approach to Phase 2. Thematic grouping was planned to identify key lessons learned.

RESULTS

Applications increased from n = 30 to n = 485 between Phase 1 and Phase 2 of the PIP, a more than 15-fold increase. The SIREN PIP positively impacted the design, implementation and evaluation phases of the study and sub-studies. Feedback from PIP members themselves was positive, with members highlighting that they found the role rewarding and felt valued. Learnings from the PIP have been condensed into five key themes for applying to future pandemic response research studies: the importance of dedicated resources; recruiting the right panel; understanding motivations for participant involvement; providing flexible options for involvement and enabling the early involvement of participants.

CONCLUSIONS

The SIREN PIP has demonstrated the value of actively involving people who research is for and about. The PIP has provided an active feedback mechanism for research and demonstrated a positive influence on both SIREN study researchers and PIP members themselves. This paper makes the case for participant involvement in future pandemic research studies. Future work should include improved training for researchers and we would support the development of a national PIP forum as part of future pandemic research preparedness.

Antibodies targeting a quaternary site on SARS-CoV-2 spike glycoprotein prevent viral receptor engagement by conformational locking

SARS-CoV-2 continues to evolve, with many variants evading clinically authorized antibodies. To isolate monoclonal antibodies (mAbs) with broadly neutralizing capacities against the virus, we screened serum samples from convalescing COVID-19 patients. We isolated two mAbs, 12-16 and 12-19, which neutralized all SARS-CoV-2 variants tested, including the XBB subvariants, and prevented infection in hamsters challenged with Omicron BA.1 intranasally. Structurally, both antibodies targeted a conserved quaternary epitope located at the interface between the N-terminal domain and subdomain 1, uncovering a site of vulnerability on SARS-CoV-2 spike. These antibodies prevented viral receptor engagement by locking the receptor-binding domain (RBD) of spike in the down conformation, revealing a mechanism of virus neutralization for non-RBD antibodies. Deep mutational scanning showed that SARS-CoV-2 could mutate to escape 12-19, but such mutations are rarely found in circulating viruses. Antibodies 12-16 and 12-19 hold promise as prophylactic agents for immunocompromised persons who do not respond robustly to COVID-19 vaccines.

T cell responses to SARS-CoV-2

This chapter provides a comprehensive analysis of T cell responses in COVID-19, focusing on T cell differentiation, specificity, and functional characteristics during SARS-CoV-2 infection. The differentiation of T cells in COVID-19 is explored, highlighting the key factors that influence T cell fate and effector functions. The immunology of the spike protein, a critical component of SARS-CoV-2, is discussed in detail, emphasizing its role in driving T-cell responses. The cellular immune responses against SARS-CoV-2 during acute infection are examined, including the specificity, phenotype, and functional attributes of SARS-CoV-2-specific T-cell responses. Furthermore, the chapter explores T-cell cross-recognition against other human coronaviruses (HCoVs) and the mechanisms of immune regulation mediated by spike proteins. This includes the induction of regulation through the innate immune system, the activation of self-spike protein-cross-reactive regulatory T cells, and the impact of self-tolerance on the regulation of spike proteins. The chapter investigates T cell responses to self-spike proteins and their implications in disease. The role of spike proteins as immunological targets in the context of COVID-19 is examined, shedding light on potential therapeutic interventions and clinical trials in autoimmune diseases. In conclusion, this chapter provides a comprehensive understanding of T cell responses in COVID-19, highlighting their differentiation, immune regulation, and clinical implications. This knowledge contributes to the development of targeted immunotherapies, vaccine strategies, and diagnostic approaches for COVID-19 and other related diseases.

Risk preferences, preventive behaviour, and the probability of a loss: Empirical evidence from the COVID-19 pandemic

RATIONALE

A theoretical model of optimal choice under risk, in which an individual chooses the level of prevention to avoid a loss, has the ambiguous prediction that a higher risk-taking preference increases the probability of a loss.

OBJECTIVE

To empirically investigate the prediction in the case of COVID-19 with individual-level survey data.

DATA

Survey data from the Understanding America Study (UAS). The UAS Coronavirus Tracking Survey followed 8628 respondents from March 2020 until July 2021 (29 survey waves) and data was gathered on having contracted COVID-19, vaccination, and preventive behaviour. Separate UAS modules gathered data on individuals' risk preferences; twice before and once during the COVID-19 pandemic. UAS also gathered data on pre-pandemic health and socio-economic status. Combining these data, and dropping missing observations, provided longitudinal data for 4335 respondents (96,370 observations) of whom 530 contracted COVID-19.

RESULTS

In support of the theoretical prediction, the empirical findings show that a one-standard deviation higher risk-taking preference is associated with about a one-third higher probability of contracting COVID-19 within two weeks. Furthermore, the findings show that individuals' risk-taking preference is negatively associated with the preventive behaviour of social distancing and not associated with getting vaccinated. There is, however, no support for preventive behaviour being associated with the probability of contracting COVID-19. The exception is for being vaccinated, which is negatively associated with the probability of contracting COVID-19. The findings, therefore, do not support that the positive association of the risk-taking preference with the probability of contracting COVID-19 is mediated through observed preventive behaviour.

CONCLUSIONS

The findings support the importance of individuals' risk-taking behaviour for contracting COVID-19 and, more generally, the importance of loss prevention as a risk management tool for individuals.

Real-time surveillance of international SARS-CoV-2 prevalence using systematic traveller arrival screening: An observational study

BACKGROUND

Effective Coronavirus Disease 2019 (COVID-19) response relies on good knowledge of population infection dynamics, but owing to under-ascertainment and delays in symptom-based reporting, obtaining reliable infection data has typically required large dedicated local population studies. Although many countries implemented Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) testing among travellers, it remains unclear how accurately arrival testing data can capture international patterns of infection, because those arrival testing data were rarely reported systematically, and predeparture testing was often in place as well, leading to nonrepresentative infection status among arrivals.

METHODS AND FINDINGS

In French Polynesia, testing data were reported systematically with enforced predeparture testing type and timing, making it possible to adjust for nonrepresentative infection status among arrivals. Combining statistical models of polymerase chain reaction (PCR) positivity with data on international travel protocols, we reconstructed estimates of prevalence at departure using only testing data from arrivals. We then applied this estimation approach to the United States of America and France, using data from over 220,000 tests from travellers arriving into French Polynesia between July 2020 and March 2022. We estimated a peak infection prevalence at departure of 2.1% (95% credible interval: 1.7, 2.6%) in France and 1% (95% CrI: 0.63, 1.4%) in the USA in late 2020/early 2021, with prevalence of 4.6% (95% CrI: 3.9, 5.2%) and 4.3% (95% CrI: 3.6, 5%), respectively, estimated for the Omicron BA.1 waves in early 2022. We found that our infection estimates were a leading indicator of later reported case dynamics, as well as being consistent with subsequent observed changes in seroprevalence over time. We did not have linked data on traveller demography or unbiased domestic infection estimates (e.g., from random community infection surveys) in the USA and France. However, our methodology would allow for the incorporation of prior data from additional sources if available in future.

CONCLUSIONS

As well as elucidating previously unmeasured infection dynamics in these countries, our analysis provides a proof-of-concept for scalable and accurate leading indicator of global infections during future pandemics.

Herd immunity, vaccination and moral obligation

The public health benefits of herd immunity are often used as the justification for coercive vaccine policies. Yet, 'herd immunity' as a term has multiple referents, which can result in ambiguity, including regarding its role in ethical arguments. The term 'herd immunity' can refer to (1) the herd immunity threshold, at which models predict the decline of an epidemic; (2) the percentage of a population with immunity, whether it exceeds a given threshold or not; and/or (3) the indirect benefit afforded by collective immunity to those who are less immune. Moreover, the accumulation of immune individuals in a population can lead to two different outcomes: elimination (for measles, smallpox, etc) or endemic equilibrium (for COVID-19, influenza, etc). We argue that the strength of a moral obligation for individuals to contribute to herd immunity through vaccination, and by extension the acceptability of coercion, will depend on how 'herd immunity' is interpreted as well as facts about a given disease or vaccine. Among other things, not all uses of 'herd immunity' are equally valid for all pathogens. The optimal conditions for herd immunity threshold effects, as illustrated by measles, notably do not apply to the many pathogens for which reinfections are ubiquitous (due to waning immunity and/or antigenic variation). For such pathogens, including SARS-CoV-2, mass vaccination can only be expected to delay rather than prevent new infections, in which case the obligation to contribute to herd immunity is much weaker, and coercive policies less justifiable.

Lessons from COVID-19 for rescalable data collection

Novel data and analyses have had an important role in informing the public health response to the COVID-19 pandemic. Existing surveillance systems were scaled up, and in some instances new systems were developed to meet the challenges posed by the magnitude of the pandemic. We describe the routine and novel data that were used to address urgent public health questions during the pandemic, underscore the challenges in sustainability and equity in data generation, and highlight key lessons learnt for designing scalable data collection systems to support decision making during a public health crisis. As countries emerge from the acute phase of the pandemic, COVID-19 surveillance systems are being scaled down. However, SARS-CoV-2 resurgence remains a threat to global health security; therefore, a minimal cost-effective system needs to remain active that can be rapidly scaled up if necessary. We propose that a retrospective evaluation to identify the cost-benefit profile of the various data streams collected during the pandemic should be on the scientific research agenda.

Burden of stillbirths among women vaccinated with COVID-19 vaccines: A systematic review and meta-analysis

OBJECTIVE

To estimate the global burden of stillbirths among pregnant women with the COVID-19 vaccination.

DATA SOURCE

In this systematic review and meta-analysis, a literature search was carried out in PubMed, Cochrane and Scopus until February 4, 2023, with language restriction (English).

STUDY SELECTION

Title-abstract screening followed by full text review was done independently by two authors, based on the research question, "What is the prevalence of stillbirths among the pregnant women vaccinated with COVID-19 vaccines?"

DATA EXTRACTION

Two authors independently extracted the relevant data from every study. The third author resolved the conflicts. This study was registered in PROSPERO and followed the PRISMA guidelines.

DATA ANALYSIS

A Random effects model was applied to assess the pooled estimate of stillbirths. The I2 test was used to assess the heterogeneity of the articles included in the study. For checking the publication bias, the Doi plot and the contour-enhanced funnel plot were utilized.

RESULTS

The database systematic search yielded 168 articles; 11 of them were determined to be eligible for systematic review and 8 of them ended up being included for meta-analysis. The pooled prevalence of stillbirth in pregnant women vaccinated against COVID-19 infection was 0.00509 (5 per 1000 live births delivered by pregnant women vaccinated against COVID-19 (95% CI: 0.00003-0.01676). Statistically significant heterogeneity was reported across studies (I2 = 98%; p < 0.01).

CONCLUSIONS

The study concluded that vaccination against COVID-19 among pregnant women had a low stillbirth rate. It adds to the existing evidence that the COVID-19 vaccine is safe and can be taken during pregnancy.

Primary series COVID-19 vaccine effectiveness among healthcare workers in Albania, February-December 2021

Background

Healthcare workers have experienced high rates of morbidity and mortality from coronavirus disease 2019 (COVID-19).

Methods

A prospective cohort study was conducted in three Albanian hospitals between 19 February and 14 December 2021. All participants underwent polymerase chain reaction (PCR) and serological testing at enrolment, regular serology throughout, and PCR testing when symptomatic.Vaccine effectiveness (VE) against COVID-19 and against all severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) infections (symptomatic or asymptomatic) was estimated. VE was estimated using a Cox regression model, with vaccination status as a time-varying variable.

Findings

In total, 1504 HCWs were enrolled in this study; 70% had evidence of prior SARS-CoV-2 infection. VE was 65.1% [95% confidence interval (CI) 37.7-80.5] against COVID-19, 58.2% (95% CI 15.7-79.3) among participants without prior SARS-CoV-2 infection, and 73.6% (95% CI 24.3-90.8) among participants with prior SARS-CoV-2 infection. For BNT162b2 alone, VE was 69.5% (95% CI 44.5-83.2). During the period when the Delta variant was predominant, VE was 67.1% (95% CI 38.3-82.5). VE against SARS-CoV-2 infection for the full study period was 36.9% (95% CI 15.8-52.7).

Interpretation

This study found moderate primary series VE against COVID-19 among healthcare workers in Albania. These results support the continued promotion of COVID-19 vaccination in Albania, and highlight the benefits of vaccination in populations with high levels of prior infection.

COVID-19 vaccine coverage targets to inform reopening plans in a low incidence setting

Since the emergence of SARS-CoV-2 in 2019 through to mid-2021, much of the Australian population lived in a COVID-19-free environment. This followed the broadly successful implementation of a strong suppression strategy, including international border closures. With the availability of COVID-19 vaccines in early 2021, the national government sought to transition from a state of minimal incidence and strong suppression activities to one of high vaccine coverage and reduced restrictions but with still-manageable transmission. This transition is articulated in the national 're-opening' plan released in July 2021. Here, we report on the dynamic modelling study that directly informed policies within the national re-opening plan including the identification of priority age groups for vaccination, target vaccine coverage thresholds and the anticipated requirements for continued public health measures-assuming circulation of the Delta SARS-CoV-2 variant. Our findings demonstrated that adult vaccine coverage needed to be at least 60% to minimize public health and clinical impacts following the establishment of community transmission. They also supported the need for continued application of test-trace-isolate-quarantine and social measures during the vaccine roll-out phase and beyond.

Surfing Corona waves - instead of breaking them: Rethinking the role of natural immunity in COVID-19 policy

In the first two years of the pandemic, COVID-19 response policies have aimed to break Corona waves through non-pharmaceutical interventions and mass vaccination. However, for long-term strategies to be effective and efficient, and to avoid massive disruption and social harms, it is crucial to introduce the role of natural immunity in our thinking about COVID-19  (or future "Disease-X") control and prevention. We argue that any Corona or similar virus control policy must appropriately balance five key elements simultaneously: balancing the various fundamental interests of the nation, as well as the various interventions within the health sector; tailoring the prevention measures and treatments to individual needs; limiting social interaction restrictions; and balancing the role of vaccinations against the role of naturally induced immunity. Given the high infectivity of SARS-CoV-2 and its differential impact on population segments, we examine this last element in more detail and argue that an important aspect of 'living with the virus' will be to better understand the role of naturally induced immunity in our overall COVID-19 policy response. In our eyes, a policy approach that factors natural immunity should be considered for persons without major comorbidities and those having 'encountered' the antigen in the past.

Infection pre-Ad26.COV2.S-vaccination primes greater class switching and reduced CXCR5 expression by SARS-CoV-2-specific memory B cells

Neutralizing antibodies strongly correlate with protection for COVID-19 vaccines, but the corresponding memory B cells that form to protect against future infection are relatively understudied. Here we examine the effect of prior SARS-CoV-2 infection on the magnitude and phenotype of the memory B cell response to single dose Johnson and Johnson (Ad26.COV2.S) vaccination in South African health care workers. Participants were either naïve to SARS-CoV-2 or had been infected before vaccination. SARS-CoV-2-specific memory B-cells expand in response to Ad26.COV2.S and are maintained for the study duration (84 days) in all individuals. However, prior infection is associated with a greater frequency of these cells, a significant reduction in expression of the germinal center chemokine receptor CXCR5, and increased class switching. These B cell features correlated with neutralization and antibody-dependent cytotoxicity (ADCC) activity, and with the frequency of SARS-CoV-2 specific circulating T follicular helper cells (cTfh). Vaccination-induced effective neutralization of the D614G variant in both infected and naïve participants but boosted neutralizing antibodies against the Beta and Omicron variants only in participants with prior infection. In addition, the SARS-CoV-2 specific CD8+ T cell response correlated with increased memory B cell expression of the lung-homing receptor CXCR3, which was sustained in the previously infected group. Finally, although vaccination achieved equivalent B cell activation regardless of infection history, it was negatively impacted by age. These data show that phenotyping the response to vaccination can provide insight into the impact of prior infection on memory B cell homing, CSM, cTfh, and neutralization activity. These data can provide early signals to inform studies of vaccine boosting, durability, and co-morbidities.

Impact of school operating scenarios on COVID-19 transmission under vaccination in the U.S.: an agent-based simulation model

At the height of the COVID-19 pandemic, K-12 schools struggled to safely operate under the fast-changing pandemic situation. However, little is known about the impact of different school operating scenarios considering the ongoing efforts of vaccination. In this study, we deployed an agent-based simulation model to mimic disease transmission in a mid-sized community consisting of 10,000 households. A total of eight school operating scenarios were simulated, in decreasing order of restrictiveness regarding COVID-19 mitigation measures. When masks were worn at school, work, and community environments, increasing in-person education from 50% to 100% would result in only 1% increase in cumulative infections. When there were no masks nor contact tracing while schools were 100% in person, the cumulative infection increased by 86% compared to the scenario when both masking and contact tracing were in place. In the sensitivity analysis for vaccination efficacy, we found that higher vaccination efficacy was essential in reducing overall infections. Our findings showed that full in-person education was safe, especially when contact tracing, masking, and widespread vaccination were in place. If no masking nor contact tracing was practiced, the transmission would rose dramatically but eventually slow down due to herd immunity.

Pathways to Immunity: Patterns of Excess Death Across the United States and Within Closed Religious Communities

Public health officials promoted COVID-19 vaccines to limit burdens placed on the U.S. healthcare system and end the pandemic. People in some closed religious communities refused to vaccinate and likely acquired temporary immunity through infection. This paper compares the death rates in Amish, Old Order Mennonites, and conservative Mennonite groups to a rate estimated for the U.S. population. Approximately two-thirds of the U.S. population was immunized against COVID-19, while few in the Amish/Mennonite community were. We find divergent patterns. Once vaccines became available, excess deaths declined in the general population and remained elevated among Amish and Mennonites. Vaccination campaigns must consider and value the cultural beliefs of closed religious communities to be effective.

Coronavirus disease 2019 (COVID-19) among nonphysician healthcare personnel by work location at a tertiary-care center, Iowa, 2020-2021

We describe COVID-19 cases among nonphysician healthcare personnel (HCP) by work location. The proportion of HCP with coronavirus disease 2019 (COVID-19) was highest in the emergency department and lowest among those working remotely. COVID-19 and non-COVID-19 units had similar proportions of HCP with COVID-19 (13%). Cases decreased across all work locations following COVID-19 vaccination.

Longitudinal study of humoral immunity against SARS-CoV-2 of health professionals in Brazil: the impact of booster dose and reinfection on antibody dynamics

Introduction

The pandemic caused by SARS-CoV-2 has had a major impact on health systems. Vaccines have been shown to be effective in improving the clinical outcome of COVID-19, but they are not able to fully prevent infection and reinfection, especially that caused by new variants.

Methods

Here, we tracked for 450 days the humoral immune response and reinfection in 52 healthcare workers from Brazil. Infection and reinfection were confirmed by RT-qPCR, while IgM and IgG antibody levels were monitored by rapid test.

Results

Of the 52 participants, 19 (36%) got reinfected during the follow-up period, all presenting mild symptoms. For all participants, IgM levels dropped sharply, with over 47% of them becoming seronegative by the 60th day. For IgG, 90% of the participants became seropositive within the first 30 days of follow-up. IgG antibodies also dropped after this period reaching the lowest level on day 270 (68.5 ± 72.3, p<0.0001). Booster dose and reinfection increased the levels of both antibodies, with the interaction between them resulting in an increase in IgG levels of 130.3 arbitrary units.

Conclusions

Overall, our data indicate that acquired humoral immunity declines over time and suggests that IgM and IgG antibody levels are not associated with the prevention of reinfection.

Kinetics of specific anti-SARS-CoV-2 IgM, IgA, and IgG responses during the first 12 months after SARS-CoV-2 infection: A prospective longitudinal study

Coronavirus 2019 (COVID-19) is a global health threat. The kinetics of antibodies against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) need to be assessed, as the long-term duration of these immunoglobulins remains largely controversial. The aim of this study was to assess the longitudinal dynamics of anti-SARS-CoV-2 antibodies against the nucleocapsid (N) protein and the receptor-binding domain (RBD) of the spike protein up to one year in a cohort of 190 COVID-19 patients. Between March and September 2021, we enrolled patients from two regional hospitals in Casablanca, Morocco. Blood samples were collected and analyzed for antibody levels. We used the commercial Euroimmun ELISA for the determination of anti-N IgM, the Abbott Architect™ SARS-CoV-2 IgG test for the detection of anti-RBD IgG, and an in-house kit for the assay of anti-N IgG and anti-N IgA. IgM and IgA antibodies were assessed 2-5, 9-12, 17-20 and 32-37 days after symptom onset. IgG antibodies were also assessed 60, 90, 120 and 360 days after symptom onset. One-third of patients developed IgM (32%), while two-thirds developed IgA (61%). One month of symptom onset, most patients developed IgG, with 97% and 93% positivity for anti-RBD IgG and anti-N IgG, respectively. The anti-RBD IgG positivity rate remained high up to one year of follow-up. However, the anti-N IgG positivity rate decreased over time, with only 41% of patients testing positive after one year's follow-up. IgG levels were significantly higher in older people (over 50 years) than in other study participants. We also found that patients who had received two doses of ChAdOx1 nCoV-19 vaccine prior to infection had a lower IgM response than unvaccinated patients. This difference was statistically significant two weeks after the onset of symptoms. We present the first study in Africa to measure the kinetics of antibody response (IgA, IgM and IgG) to SARS-CoV-2 over one year. Most participants remained seropositive for anti-RBD IgG after one year but showed a significant decline in antibody titers.