Persistence of Antibody and Cellular Immune Responses in COVID-19 patients over Nine Months after Infection

Otitis media with effusion in adults during the SARS-CoV-2 epidemic

OBJECTIVES

The purpose of this study was to investigate the fluctuations in the prevalence of individuals diagnosed with otitis media with effusion (OME) during the SARS-CoV-2 pandemic, while also evaluating the persistence of SARS-CoV-2 in middle ear effusion (MEE) and assessing the effectiveness of tympanocentesis as a treatment modality for OME in this specific period.

METHODS

The total number of outpatients and patients diagnosed with OME in our department was recorded for January 2022 and January 2023. Thirty patients (aged 15-86 years) were categorized into two groups: group A (n = 12), who developed OME during their SARS-CoV-2 infection and group B (n = 18), who experienced OME after the resolution of SARS-CoV-2 infection. All patients underwent otoendoscopic tympanocentesis (without a ventilation tube), where MEE and nasopharyngeal secretions were simultaneously collected for SARS-CoV-2 detection by polymerase chain reaction. The time interval from SARS-CoV-2 infection to tympanocentesis, results of SARS-CoV-2 detection, preoperative and postoperative average hearing threshold, and Eustachian Tube Dysfunction Questionnaire (ETDQ-7) scores were documented.

RESULTS

The proportion of outpatients with OME in January 2023 was higher than that in January 2022. There were five patients who had positive test results for SARS-CoV-2 on MEE after tympanocentesis. These 5 patients underwent tympanocentesis at a mean of 28 ± 7.28 days following confirmation of SARS-CoV-2 infection. The ETDQ-7 scores of group A exhibited a reduction from 21.85 ± 4.8 to 10.00 ± 4.07 following tympanocentesis, while the ETDQ-7 scores of group B also demonstrated a decrease from 21.22 ± 4.65 to 10.11 ± 3.68 after undergoing tympanocentesis. The tympanocentesis was effective in both groups.

CONCLUSIONS

The study confirmed that the proportion of outpatients with OME in the Clinics of Otolaryngology during the SARS-CoV-2 epidemic increased significantly. SARS-CoV-2 RNA was detectable in MEE of COVID-19-related OME patients. Tympanocentesis was therapeutic for OME during SARS-CoV-2 infection, which facilitated viral clearance in MEE.

Antibody response to ChAdOx1 nCoV-19 (Covishield®) vaccine in people on maintenance hemodialysis

INTRODUCTION

People on renal replacement therapy (RRT) have a high risk of COVID-19 infection and subsequent death. COVID-19 vaccination is strongly recommended for those on RRT. Data are limited on the immune response of the ChAdOx1 nCoV-19/AZD1222 (Covishield®) vaccine in patients on RRT.

METHODS

A prospective cohort of adult (age > 18 years), on RRT in the form of hemodialysis were included and received two intramuscular doses of Covishield®. A blood specimen of 5.0 mL was collected at two time points, within a few days before administering the first dose of the vaccine and at 4-16 weeks after the second dose. According to their prior COVID-19 infection status, the participants were grouped as (i) prior symptomatic COVID-19 infection, (ii) prior asymptomatic COVID-19 infection, and (iii) no prior COVID-19 infection.

RESULTS

A large proportion (81%) of participants had anti-spike antibodies (ASAb) before vaccination, and a reasonable proportion (30%) also had neutralizing antibodies (NAb). The titer of ASAb was relatively low (207 U/mL) before vaccination. The ASAb titer (9405 [1635-25,000] U/mL) and percentage of NAb (96.4% [59.6-98.1%]) were markedly increased following the administration of two doses of the vaccine. The participants' prior COVID-19 exposure status did not influence the rise in ASAb titer and NAb percentage. Further, administering two doses of the Covishield vaccine helps them achieve a high ASAb titer.

CONCLUSION

Two doses of ChAdOx1 nCoV-19/AZD1222 (Covishield®) vaccine, given 12 weeks apart, achieve a high titer of ASAb and a high percentage of NAb in people on hemodialysis.

SARS-CoV-2-specific T cell responses wane profoundly in convalescent individuals 10 months after primary infection

A key question in the coronavirus disease 2019 (COVID-19) pandemic is the duration of specific T cell responses against the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) post primary infection, which is difficult to address due to the large-scale COVID-19 vaccination and re-exposure to the virus. Here, we conducted an analysis of the long-term SARS-CoV-2-specific T cell responses in a unique cohort of convalescent individuals (CIs) that were among the first to be infected worldwide and without any possible antigen re-exposure since then. The magnitude and breadth of SARS-CoV-2-specific T cell responses correlated inversely with the time that had elapsed from disease onset and the age of those CIs. The mean magnitude of SARS-CoV-2-specific CD4 and CD8 T cell responses decreased about 82% and 76%, respectively, over the time period of ten months after infection. Accordingly, the longitudinal analysis also demonstrated that SARS-CoV-2-specific T cell responses waned significantly in 75% of CIs during the follow-up. Collectively, we provide a comprehensive characterization of the long-term memory T cell response in CIs, suggesting that robust SARS-CoV-2-specific T cell immunity post primary infection may be less durable than previously expected.

[Development and preservation of specific T-cell immunity after COVID-19 or vaccination against this infection]

Aim evaluation of specific T-cell immunity against SARS-CoV-2 in primary and secondary response to virus antigens by screening method.

MATERIALS AND METHODS

Patients were tested 11.5 months after COVID-19 and 610 months before and after vaccination. Healthy volunteers were screened before, 26 times during the vaccination course, and 68 months after revaccination with the Sputnik V vaccine. IgG and IgM antibodies to SARS-CoV-2 were detected by ELISA using commercially available kits (Vector-Best, Russia). Antigenic (AG) activation of T cells in the fraction of bloods mononuclear cells was assessed by IFN- production after AG stimulation in the wells of plates from ELISA kits intended for detection of antibodies against SARS-CoV-2. Data were processed by MS Excel and Statistica 10.0 software.

RESULTS

AG-specific T cells were detected in 88.5% of vaccinated healthy volunteers, half of whom were found to have T cells appearing earlier than antibodies to AG. After 6-8 months, the level of AG activation decreases. Following the revaccination, the level of AG activation of memory T cells in vitro increases within six months in 76.9100.0% of vaccinated subjects. On the contrary, after COVID-19, 86.7% of individuals had in their blood the AG-specific T cells with high activity at the time of vaccination. The activity of T cells recognizing the RBD domain of the SARS-CoV-2 S protein and the proportion of individuals who had these cells in their blood increased after the vaccination of reconvalescents.

CONCLUSION

T-cell immunity against SARS-CoV-2 antigens has been shown to persist for 6 months after illness. In vaccinated individuals without history of COVID-19, such duration of the preservation of AG-specific T cells in blood was only achieved after the revaccination.

Long-term evaluation of the seroprevalence of SARS-CoV-2 IgG and IgM antibodies in recovered patients: a meta-analysis

Estimating severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) -specific immunoglobulin G (IgG) immunoglobulin M (IgM) antibodies are increasingly important for tracking the spread of infection and defining herd immunity barrier and individual immunization levels in the ongoing coronavirus disease 2019 (COVID-19) pandemic. Therefore, we conducted the present systematic review and meta-analysis to evaluate the seroprevalence of SARS-CoV-2 IgM and IgG antibodies of recovered COVID-19 patients in long-term follow-up studies. A systematic search of the MEDLINE, Embase, COVID-19 Primer, PubMed, CNKI, and the Public Health England library databases was conducted. Twenty-fourth eligible studies were included. Meta-analysis showed that 27% (95%CI: 0.04-0.49) and 66% (95%CI:0.47-0.85) were seropositive for SARS-CoV-2 IgM and IgG, respectively, while in long-term 12 months following up studies, the seroprevalences of IgM antibody (17%) decreased and IgG antibody (75%) was higher than 6 months follow-up patients. However, due to the limited number of relevant studies, the high level of heterogeneity, and the large gap in studies conducted, the findings of our study may not accurately reflect the true seroprevalence status of SARS-CoV-2 infection. Nevertheless, sequential vaccination or booster immunization is considered to be a necessary long-term strategy to sustain the fight against the pandemic.

Long-term hypercoagulability, endotheliopathy and inflammation following acute SARS-CoV-2 infection

INTRODUCTION

both symptomatic and asymptomatic SARS-CoV-2 infections - coined Coronavirus disease 2019 (COVID-19) - have been linked to a higher risk of cardiovascular events after recovery.

AREAS COVERED

our review aims to summarize the latest evidence on the increased thrombotic and cardiovascular risk in recovered COVID-19 patients and to examine the pathophysiological mechanisms underlying the interplay among endothelial dysfunction, inflammatory response and coagulation in long-COVID. We performed a systematic search of studies on hypercoagulability, endothelial dysfunction and inflammation after SARS-CoV-2 infection.

EXPERT OPINION

endothelial dysfunction is a major pathophysiological mechanism responsible for most clinical manifestations in COVID-19. The pathological activation of endothelial cells by a virus infection results in a pro-adhesive and chemokine-secreting phenotype, which in turn promotes the recruitment of circulating leukocytes. Cardiovascular events after COVID-19 appear to be related to persistent immune dysregulation. Patients with long-lasting symptoms display higher amounts of proinflammatory molecules such as tumor necrosis factor-α, interferon γ and interleukins 2 and 6. Immune dysregulation can trigger the activation of the coagulation pathway. The formation of extensive microclots in vivo, both during acute COVID-19 and in long-COVID-19, appears to be a relevant mechanism responsible for persistent symptoms and cardiovascular events.

Evaluation of Cellular Responses to ChAdOx1-nCoV-19 and BNT162b2 Vaccinations

While numerous studies have evaluated humoral responses to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccines, data on the cellular responses to these vaccines remain sparse. We evaluated T cell responses to ChAdOx1-nCoV-19 and BNT162b2 vaccinations using an interferon gamma (IFN-γ) release assay (IGRA). ChAdOx1-nCoV-19- and BNT162b2-vaccinated participants initially showed stronger T cell responses than unvaccinated controls. The T cell response decreased over time and increased substantially after the administration of a BNT162b2 booster dose. Changes in the T cell response were less significant than those in the anti-receptor-binding domain IgG antibody titer. The study results can serve as baseline data for T cell responses after SARS-CoV-2 vaccination and suggest that the IGRA can be useful in monitoring immunogenicity.

Dynamics of Different Classes and Subclasses of Antibody Responses to Severe Acute Respiratory Syndrome Coronavirus 2 Variants after Coronavirus Disease 2019 and CoronaVac Vaccination in Thailand

The humoral immune response plays a key role in protecting the population from SARS-CoV-2 transmission. Patients who recovered from COVID-19 as well as fully vaccinated individuals have elevated levels of antibodies. The dynamic levels of the classes and subclasses of antibody responses to new variants that occur in different populations remain unclear. We prospectively recruited 60 participants, including COVID-19 patients and CoronaVac-vaccinated individuals, in Thailand from May to August 2021. Plasma samples were collected on day 0, day 14, and day 28 to determine the dynamic levels of the classes and subclasses of plasma antibodies against the receptor-binding domain (RBD) in the spike protein (S) of four SARS-CoV-2 strains (Wuhan, Alpha, Delta, and Omicron) via enzyme-linked immunosorbent assay. Our results indicated that the patients with SARS-CoV-2 infections had broader class and subclass profiles as well as higher levels of anti-S RBD antibodies to the Wuhan, Alpha, and Delta strains than did the CoronaVac-vaccinated individuals. The median antibody levels increased and subsequently declined in a month in the COVID-19 patients and in the vaccinated group. Correlations of the classes and subclasses of antibodies were observed in the COVID-19 patients but not in the vaccinated individuals. The levels of all of the anti-S RBD antibodies against the Omicron variant were low in the patients and in the vaccinated individuals. Our study revealed distinct antibody profiles between the two cohorts, suggesting different pathways of immune activation. This could have an impact on protection from infections by new variants of concern (VOC). IMPORTANCE The antibody responses to new SARS-CoV-2 variants that occur in different populations remain unclear. In this study, we recruited 60 participants, including COVID-19 patients and CoronaVac-vaccinated individuals, in Thailand and determined the dynamic levels of the IgG, IgA, IgM, and IgG subclasses of antibodies against the spike protein (S) of four SARS-CoV-2 strains. Our results showed that the patients with SARS-CoV-2 infections had broader profiles and higher levels of antibodies to the Wuhan, Alpha, and Delta strains than did the CoronaVac-vaccinated individuals. The antibody levels of both groups increased and subsequently decreased within 1 month. Higher and functional correlations of these antibodies were observed in the COVID-19 patients. The levels of all anti-S RBD antibodies against the Omicron variant were low in patients and vaccinated individuals. Our study revealed distinct antibody responses between the two groups, suggesting different pathways of immune response, which may have an impact on protection from infections by new SARS-CoV-2 variants.

Reactogenicity and persistence of IgG antibodies against SARS-CoV-2 among recipients of ChAdOx1 nCoV-19 vaccine: A single center experience from Sri Lanka

Objectives

Actual world data on vaccines against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) are imperative for future immunization decisions. We studied the reactogenicity and IgG response in a cohort dually vaccinated with the ChAdOx1 nCoV-19 vaccine.

Methods

This prospective study recruited 494 ChAdOx1 nCoV-19 vaccine recipients at the University Hospital KDU between January 30 and February 5, 2021, and followed up for 9 months. The two doses of the vaccine were administered 3-month apart, followed by a booster dose with the BNT162b2 (Pfizer-BioNTech) vaccine 6 months later. One-week post-vaccination surveillance ascertained the reactogenicity of the vaccine. Seroprevalence of IgG antibodies before each vaccination dose was determined using a commercially available quantitative ELISA kit (WANTAI SARS-CoV-2 IgG Quantitative ELISA Beijing China). Reactogenicity profiles after vaccination doses were compared. Association of pre-vaccination seropositivity and demographic variables with antibody levels was assessed.

Results

Reactogenicity was reported by 78.5% (329/419) and 25.4% (104/410) participants after the first and second doses, respectively, with a significantly high mean total score of vaccine-related symptoms following the first dose (P = 0.015). Post-first dose seroconversion rate was 97.1%, and the immune response was more robust among pre-vaccination seropositive participants and females. Following the second dose, 100% seroconversion was observed. Subgroup analysis of 196 participants revealed persistent antibodies at nine months with a rise in the previously measured levels among 78.1% compared to 21.9% with declining titers. Antibody waning was significantly associated with pre-vaccination seropositivity (P = 0.015) and female gender (P = 0.022).

Conclusions

High seroconversion rates and longevity of antibody response in the absence of serious concerns regarding reactogenicity suggest that the vaccine is immunogenic and safe. Significant antibody waning among females and pre-vaccination seropositive participants warrant further research.

Immune correlates of protection for SARS-CoV-2, Ebola and Nipah virus infection

Correlates of protection (CoP) are biological parameters that predict a certain level of protection against an infectious disease. Well-established correlates of protection facilitate the development and licensing of vaccines by assessing protective efficacy without the need to expose clinical trial participants to the infectious agent against which the vaccine aims to protect. Despite the fact that viruses have many features in common, correlates of protection can vary considerably amongst the same virus family and even amongst a same virus depending on the infection phase that is under consideration. Moreover, the complex interplay between the various immune cell populations that interact during infection and the high degree of genetic variation of certain pathogens, renders the identification of immune correlates of protection difficult. Some emerging and re-emerging viruses of high consequence for public health such as SARS-CoV-2, Nipah virus (NiV) and Ebola virus (EBOV) are especially challenging with regards to the identification of CoP since these pathogens have been shown to dysregulate the immune response during infection. Whereas, virus neutralising antibodies and polyfunctional T-cell responses have been shown to correlate with certain levels of protection against SARS-CoV-2, EBOV and NiV, other effector mechanisms of immunity play important roles in shaping the immune response against these pathogens, which in turn might serve as alternative correlates of protection. This review describes the different components of the adaptive and innate immune system that are activated during SARS-CoV-2, EBOV and NiV infections and that may contribute to protection and virus clearance. Overall, we highlight the immune signatures that are associated with protection against these pathogens in humans and could be used as CoP.

Dynamics of Antibody and T Cell Immunity against SARS-CoV-2 Variants of Concern and the Impact of Booster Vaccinations in Previously Infected and Infection-Naïve Individuals

Despite previous coronavirus disease 2019 (COVID-19) vaccinations and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infections, SARS-CoV-2 still causes a substantial number of infections due to the waning of immunity and the emergence of new variants. Here, we assessed the SARS-CoV-2 spike subunit 1 (S1)-specific T cell responses, anti-SARS-CoV-2 receptor-binding domain (RBD) IgG serum concentrations, and the neutralizing activity of serum antibodies before and one, four, and seven months after the BNT162b2 or mRNA-1273 booster vaccination in a cohort of previously infected and infection-naïve healthcare workers (HCWs). Additionally, we assessed T cell responses against the spike protein of the SARS-CoV-2 Delta, Omicron BA.1 and BA.2 variants of concern (VOC). We found that S1-specific T cell responses, anti-RBD IgG concentrations, and neutralizing activity significantly increased one month after booster vaccination. Four months after booster vaccination, T cell and antibody responses significantly decreased but levels remained steady thereafter until seven months after booster vaccination. After a similar number of vaccinations, previously infected individuals had significantly higher S1-specific T cell, anti-RBD IgG, and neutralizing IgG responses than infection-naïve HCWs. Strikingly, we observed overall cross-reactive T cell responses against different SARS-CoV-2 VOC in both previously infected and infection-naïve HCWs. In summary, COVID-19 booster vaccinations induce strong T cell and neutralizing antibody responses and the presence of T cell responses against SARS-CoV-2 VOC suggest that vaccine-induced T cell immunity offers cross-reactive protection against different VOC.

SARS-CoV-2-The Role of Natural Immunity: A Narrative Review

BACKGROUND

Both natural immunity and vaccine-induced immunity to COVID-19 may be useful to reduce the mortality/morbidity of this disease, but still a lot of controversy exists.

AIMS

This narrative review analyzes the literature regarding these two immunitary processes and more specifically: (a) the duration of natural immunity; (b) cellular immunity; (c) cross-reactivity; (d) the duration of post-vaccination immune protection; (e) the probability of reinfection and its clinical manifestations in the recovered patients; (f) the comparisons between vaccinated and unvaccinated as to the possible reinfections; (g) the role of hybrid immunity; (h) the effectiveness of natural and vaccine-induced immunity against Omicron variant; (i) the comparative incidence of adverse effects after vaccination in recovered individuals vs. COVID-19-naïve subjects.

MATERIAL AND METHODS

through multiple search engines we investigated COVID-19 literature related to the aims of the review, published since April 2020 through July 2022, including also the previous articles pertinent to the investigated topics.

RESULTS

nearly 900 studies were collected, and 246 pertinent articles were included. It was highlighted that the vast majority of the individuals after suffering from COVID-19 develop a natural immunity both of cell-mediated and humoral type, which is effective over time and provides protection against both reinfection and serious illness. Vaccine-induced immunity was shown to decay faster than natural immunity. In general, the severity of the symptoms of reinfection is significantly lower than in the primary infection, with a lower degree of hospitalizations (0.06%) and an extremely low mortality.

CONCLUSIONS

this extensive narrative review regarding a vast number of articles highlighted the valuable protection induced by the natural immunity after COVID-19, which seems comparable or superior to the one induced by anti-SARS-CoV-2 vaccination. Consequently, vaccination of the unvaccinated COVID-19-recovered subjects may not be indicated. Further research is needed in order to: (a) measure the durability of immunity over time; (b) evaluate both the impacts of Omicron BA.5 on vaccinated and healed subjects and the role of hybrid immunity.

Prevalence, incidence and longevity of antibodies against SARS-CoV-2 among primary healthcare providers in Belgium: a prospective cohort study with 12 months of follow-up

OBJECTIVES

To estimate the prevalence, incidence and longevity of antibodies against SARS-CoV-2 among primary healthcare providers (PHCPs).

DESIGN

Prospective cohort study with 12 months of follow-up.

SETTING

Primary care in Belgium.

PARTICIPANTS

Any general practitioner (GP) working in primary care in Belgium and any other PHCP from the same GP practice who physically manages (examines, tests, treats) patients were eligible. A convenience sample of 3648 eligible PHCPs from 2001 GP practices registered for this study (3044 and 604 to start in December 2020 and January 2021, respectively). 3390 PHCPs (92,9%) participated in their first testing time point (2820 and 565, respectively) and 2557 PHCPs (70,1%) in the last testing time point (December 2021).

INTERVENTIONS

Participants were asked to perform a rapid serological test targeting IgM and IgG against the receptor binding domain of SARS-CoV-2 and to complete an online questionnaire at each of maximum eight testing time points.

PRIMARY AND SECONDARY OUTCOME MEASURES

The prevalence, incidence and longevity of antibodies against SARS-CoV-2 both after natural infection and after vaccination.

RESULTS

Among all participants, 67% were women and 77% GPs. Median age was 43 years. The seroprevalence in December 2020 (before vaccination availability) was 15.1% (95% CI 13.5% to 16.6%), increased to 84.2% (95% CI 82.9% to 85.5%) in March 2021 (after vaccination availability) and reached 93.9% (95% CI 92.9% to 94.9%) in December 2021 (during booster vaccination availability and fourth (delta variant dominant) COVID-19 wave). Among not (yet) vaccinated participants the first monthly incidence of antibodies against SARS-CoV-2 was estimated to be 2.91% (95% CI 1.80% to 4.01%). The longevity of antibodies is higher in PHCPs with self-reported COVID-19 infection.

CONCLUSIONS

This study confirms that occupational health measures provided sufficient protection when managing patients. High uptake of vaccination resulted in high seroprevalence of SARS-CoV-2 antibodies in PHCPs in Belgium. Longevity of antibodies was supported by booster vaccination and virus circulation.

TRIAL REGISTRATION NUMBER

NCT04779424.

Heterogenous humoral and cellular immune responses with distinct trajectories post-SARS-CoV-2 infection in a population-based cohort

To better understand the development of SARS-CoV-2-specific immunity over time, a detailed evaluation of humoral and cellular responses is required. Here, we characterize anti-Spike (S) IgA and IgG in a representative population-based cohort of 431 SARS-CoV-2-infected individuals up to 217 days after diagnosis, demonstrating that 85% develop and maintain anti-S responses. In a subsample of 64 participants, we further assess anti-Nucleocapsid (N) IgG, neutralizing antibody activity, and T cell responses to Membrane (M), N, and S proteins. In contrast to S-specific antibody responses, anti-N IgG levels decline substantially over time and neutralizing activity toward Delta and Omicron variants is low to non-existent within just weeks of Wildtype SARS-CoV-2 infection. Virus-specific T cells are detectable in most participants, albeit more variable than antibody responses. Cluster analyses of the co-evolution of antibody and T cell responses within individuals identify five distinct trajectories characterized by specific immune patterns and clinical factors. These findings demonstrate the relevant heterogeneity in humoral and cellular immunity to SARS-CoV-2 while also identifying consistent patterns where antibody and T cell responses may work in a compensatory manner to provide protection.

The persistence of the immune response to SARS-CoV-2 after recovery from infection is an indicator for subsequent protection against infection. Here the authors follow recovered patients and measure antibody and T cell responses and find that these two parts of the immune response may have different longevity.

Determining SARS-CoV-2 non-infectivity state-A brief overview

From the beginning of the COVID-19 pandemic, it has claimed over 6 million lives, and globally the pandemic rages with detrimental consequences, with the emergence of new more infectious and possibly virulent variants. A clinical obstacle in this battle has been to determine when an infected individual has reached a non-infectious state. Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) can be transmitted under diverse circumstances, and various rules and regulations, along with different testing methods, have been applied in an attempt to confine the transmission. However, that has proven to be a difficult task. In this review, we take together recently published data on infectivity and transmission of SARS-CoV-2 and have combined it with the clinical experience that physicians in Iceland have accumulated from the pandemic. In addition, we suggest guidelines for determining when patients with COVID-19 reach a non-infectious state based on a combination of clinical experience, scientific data, and proficient use of available tests. This review has addressed some of the questions regarding contagiousness and immunity against SARS-CoV-2.

High secondary attack rate and persistence of SARS-CoV-2 antibodies in household transmission study participants, Finland 2020–2021

Background

Household transmission studies offer the opportunity to assess both secondary attack rate (SAR) and persistence of SARS-CoV-2 antibodies over time.

Methods

In Spring 2020, we invited confirmed COVID-19 cases and their household members to four visits, where we collected nasopharyngeal and serum samples over 28 days after index case onset. We calculated SAR based on the presence of SARS-CoV-2 neutralizing antibodies (NAb) and assessed the persistence of NAb and IgG antibodies (Ab) against SARS-CoV-2 spike glycoprotein and nucleoprotein.

Results

SAR was 45% (39/87), including 35 symptomatic secondary cases. During the initial 28-day follow-up, 62% (80/129) of participants developed NAb. Of those that seroconverted, 90% (63/70), 85% (63/74), and 78% (45/58) still had NAb to early B-lineage SARS-CoV-2 3, 6, and 12 months after the onset of the index case. Anti-spike IgG Ab persisted in 100% (69/69), 97% (72/74), and 93% (55/59) of seroconverted participants after 3, 6, and 12 months, while anti-nucleoprotein IgG Ab levels waned faster, persisting in 99% (68/69), 78% (58/74), and 55% (39/71) of participants, respectively.

Conclusion

Following detection of a COVID-19 case in a household, other members had a high risk of becoming infected. NAb to early B-lineage SARS-CoV-2 persisted for at least a year in most cases.

Durability of SARS-CoV-2 Specific IgG Antibody Responses Following Two Doses of Match and Mixed COVID-19 Vaccines Regimens in Saudi Population

Background

SARS-CoV-2 pandemic continues to threaten the human population with millions of infections and deaths worldwide. Vaccination campaigns undertaken by several countries have resulted in a notable decrease in hospitalization and deaths. However, with the emergence of new virus variants, it is critical to determine the longevity and the protection efficiency provided by the current authorized vaccines.

Aim

The aims of this study are to provide data about the magnitude of immune responses in individuals fully vaccinated against COVID-19 in Riyadh province of Saudi Arabia. Also, to evaluate the continuity of specific IgG levels and compare the titers in individuals who have been received two doses of the matched and mixed vaccines, including Pfizer and AstraZeneca against SARS-CoV-2 during the period of three to six months. Moreover, we analyze the current state of immune response in terms of antibody responses in thepopulation postvaccination using homogenous or hetrogenous vaccine regimen.

Methods

A total of 141 healthy volunteers were recruited to our study; blood (n=63) and the saliva samples (n=78) and were collected from fully vaccinated individuals in Riyadh city. We employed a specific ELISA assay in plasma and saliva of fully vaccinated individuals.

Results

IgG levels varied with age groups with the highest concentration in the age group 19–29 years, but the age group (≥50) had the lowest IgG concentration. The IgG levels in both serum and saliva were higher after three months and start to wane after six months. Individuals who received mixed types of vaccines had significantly better response than Pfizer vaccine alone.

Conclusion

The current study investigates the status of humoral responses in different age groups, in terms of antibody measurements. These data will help to evaluate the need for further COVID-19 vaccine doses and to what extent a two-dose regimen will protect vaccinated individuals.

Long COVID and the cardiovascular system - elucidating causes and cellular mechanisms in order to develop targeted diagnostic and therapeutic strategies: A joint Scientific Statement of the ESC Working Groups on Cellular Biology of the Heart and Myocardial & Pericardial Diseases

Long COVID has become a world-wide, non-communicable epidemic, caused by long-lasting multi-organ symptoms that endure for weeks or months after SARS-CoV-2 infection has already subsided. This scientific document aims to provide insight into the possible causes and therapeutic options available for the cardiovascular manifestations of long COVID. In addition to chronic fatigue, which is a common symptom of long COVID, patients may present with chest pain, ECG abnormalities, postural orthostatic tachycardia, or newly developed supraventricular or ventricular arrhythmias. Imaging of the heart and vessels has provided evidence of chronic, post-infectious peri-myocarditis with consequent left or right ventricular failure, arterial wall inflammation or micro-thrombosis in certain patient populations. Better understanding of the underlying cellular and molecular mechanisms of long COVID will aid in the development of effective treatment strategies for its cardiovascular manifestations. A number of mechanisms have been proposed, including those involving direct effects on the myocardium, micro-thrombotic damage to vessels or endothelium, or persistent inflammation. Unfortunately, existing circulating biomarkers, coagulation and inflammatory markers, are not highly predictive for either the presence or outcome of long COVID when measured 3 months after SARS-CoV-2 infection. Further studies are needed to understand underlying mechanisms, identify specific biomarkers and guide future preventive strategies or treatments to address long COVID and its cardiovascular sequelae.

Antibodies to the Spike Protein Receptor-Binding Domain of SARS-CoV-2 at 4–13 Months after COVID-19

Identification of factors behind the level and duration of persistence of the SARS-CoV-2 antibodies in the blood is assumed to set the direction for studying humoral immunity mechanisms against COVID-19, optimizing the strategy for vaccine use, antibody-based drugs, and epidemiological control of COVID-19. Objective: This study aimed to study the relationship between clinical and demographic characteristics and the level of IgG antibodies to the RBD of SARS-CoV-2 spike protein after COVID-19 in the long term. Residents of the Altai Region of Western Siberia of Russia, Caucasians, aged from 27 to 93 years (median 53.0 years), who recovered from COVID-19 between May 2020 and February 2021 (n = 44) took part in this prospective observational study. The titer of IgG antibodies to the RBD of SARS-CoV-2 spike protein was measured repeatedly in the blood at 4–13 months from the beginning of the clinical manifestation of COVID-19 via the method of enzyme-linked immunosorbent assay. The antibody titer positively correlated with age (p = 0.013) and COVID-19 pneumonia (p = 0.002) at 20–40 and 20–24 weeks from the onset of COVID-19 symptoms, respectively. Age was positively associated with antibody titer regardless of history of COVID-19 pneumonia (beta regression coefficient p = 0.009). The antibody titer decreased in 15 (34.1%) patients, increased in 10 (22.7%) patients, and did not change in 19 (43.2%) patients from the baseline to 48–49 weeks from the onset of COVID-19 symptoms, with seropositivity persisting in all patients. Age and COVID-19 pneumonia are possibly associated with higher IgG antibodies to the spike protein RBD of SARS-CoV-2 following COVID-19 in the long term. Divergent trends of anti-RBD IgG levels in adults illustrate inter-individual differences at 4–13 months from the onset of COVID-19 symptoms.

Serology suggests adequate safety measures to protect healthcare workers from COVID-19 in Shiga Prefecture, Japan

Healthcare workers (HCWs), especially frontline workers against coronavirus disease 2019 (COVID-19), are considered to be risky because of occupational exposure to infected patients. This study evaluated the correlation between seroprevalence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) antibodies among HCWs and the implementation of personal protective equipment (PPE) & infection prevention and control (IPC). We recruited 1237 HCWs from nine public COVID-19-designated hospitals in Shiga Prefecture, central Japan, between 15-26 February 2021. All participants answered a self-administered questionnaire and provided blood samples to evaluate SARS-CoV-2 antibodies. A total of 22 cases (1·78%) were seropositive among the 1237 study participants. An unavoidable outbreak of SARS-CoV-2 had occurred at the terminal care unit of one hospital, before identifying and securely isolating this cluster of cases. Excluding with this cluster, 0·68% of HCWs were suspected to have had previous SARS-CoV-2 infections. Binomial logistic regression from individual questionnaires and seropositivity predicted a significant correlation with N95 mask implementation under aerosol conditions (p = 8.63e-06, aOR = 2.47) and work duration in a red zone (p = 2.61e-04, aOR = 1.99). The institutional questionnaire suggested that IPC education was correlated with reduced seropositivity at hospitals. Seroprevalence and questionnaire analyses among HCWs indicated that secure implementation of PPE and re-education of IPC are essential to prevent SARS-CoV-2 infection within healthcare facilities. Occupational infections from SARS-CoV-2 in healthcare settings could be prevented by adhering to adequate measures and appropriate use of PPE. With these measures securely implemented, HCWs should not be considered against as significantly risky or dirty by local communities.

Factors Associated With the Decay of Anti-SARS-CoV-2 S1 IgG Antibodies Among Recipients of an Adenoviral Vector-Based AZD1222 and a Whole-Virion Inactivated BBV152 Vaccine

Background

The magnitude of protection conferred following recovery from COVID-19 or by vaccine administration, and the duration of protective immunity developed, remains ambiguous.

Methods

We investigated the factors associated with anti-SARS-CoV-2 S1 IgG decay in 519 individuals who recovered from COVID-19 illness or received COVID-19 vaccination with two commercial vaccines, viz., an adenoviral vector-based (AZD1222) and a whole-virion-based inactivated (BBV152) vaccine in Chennai, India from March to December 2021. Blood samples collected during regular follow-up post-infection/-vaccination were examined for anti-SARS-CoV-2 S1 IgG by a commercial automated chemiluminescent immunoassay (CLIA).

Results

Age and underlying comorbidities were the two variables that were independently associated with the development of a breakthrough infection. Individuals who were >60 years of age with underlying comorbid conditions (viz., hypertension, diabetes mellitus and cardiovascular disease) had a ~15 times and ~10 times greater odds for developing a breakthrough infection and hospitalization, respectively. The time elapsed since the first booster dose was associated with attrition in anti-SARS-CoV-2 IgG, where each month passed was associated with an ebb in the anti-SARS-CoV-2 IgG antibody levels by a coefficient of -6 units.

Conclusions

Our findings advocate that the elderly with underlying comorbidities be administered with appropriate number of booster doses with AZD1222 and BBV152 against COVID-19.

Antibody Response Three Months After SARS-CoV-2 Infection

The Coronavirus disease-19 (COVID-19) pandemic became the greatest public health challenge globally. In our study, it was aimed to determine the antibody levels in the 3rd month after the COVID-19 infection and the symptoms that continued until the 3rd month from the onset of the infection. One hundred people who applied to Tarsus State Hospital with the suspicion of COVID-19 and were positive for SARS-CoV-2 infection by real-time reverse transcriptase-polymerase chain reaction (RT-qPCR) were included. We collected serum samples from individuals, who were three months post-infection, and tested them in Anti-SARS-CoV-2 Quanti-Vac ELISA IgG (Euroimmun, Lubeck, Germany) kit coated with recombinant S1 antigen for testing SARS-CoV-2 antibodies. Antibody levels were found to be higher in those aged ≥55 years, non-smokers, those with comorbidities, and those who were hospitalized. The four most common symptoms that individuals initially encounter; are weakness, muscle and joint pain, loss of taste and smell, and cough. In three months after COVID-19 infection, the most common four symptoms are; muscle and joint pain, insomnia, fatigue, and other problems were determined. In conclusion; more research is needed to determine threshold levels of serum antibodies that could prevent reinfection of SARS-CoV-2. This article is protected by copyright. All rights reserved.

Multiple Routes of Antibody-Dependent Enhancement of SARS-CoV-2 Infection

Antibody-dependent enhancement (ADE) of infection is generally known for many viruses. A potential risk of ADE in severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection has also been discussed since the beginning of the coronavirus disease 2019 (COVID-19) pandemic; however, clinical evidence of the presence of antibodies with ADE potential is limited. Here, we show that ADE antibodies are produced by SARS-CoV-2 infection and the ADE process can be mediated by at least two different host factors, Fcγ receptor (FcγR) and complement component C1q. Of 89 serum samples collected from acute or convalescent COVID-19 patients, 62.9% were found to be positive for SARS-CoV-2-specific IgG. FcγR- and/or C1q-mediated ADE were detected in 50% of the IgG-positive sera, whereas most of them showed neutralizing activity in the absence of FcγR and C1q. Importantly, ADE antibodies were found in 41.4% of the acute COVID-19 patients. Neutralizing activity was also detected in most of the IgG-positive sera, but it was counteracted by ADE in subneutralizing conditions in the presence of FcγR or C1q. Although the clinical importance of ADE needs to be further investigated with larger numbers of COVID-19 patient samples, our data suggest that SARS-CoV-2 utilizes multiple mechanisms of ADE. C1q-mediated ADE may particularly have a clinical impact since C1q is present at high concentrations in plasma and its receptors are ubiquitously expressed on the surfaces of many types of cells, including respiratory epithelial cells, which SARS-CoV-2 primarily infects.

IMPORTANCE Potential risks of antibody-dependent enhancement (ADE) in the coronavirus disease 2019 (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection has been discussed and the proposed mechanism mostly depends on the Fc gamma receptor (FcγR). However, since FcγRs are exclusively expressed on immune cells, which are not primary targets of SARS-CoV-2, the clinical importance of ADE of SARS-CoV-2 infection remains controversial. Our study demonstrates that SARS-CoV-2 infection induces antibodies that increase SARS-CoV-2 infection through another ADE mechanism in which complement component C1q mediates the enhancement. Although neutralizing activity was also detected in the serum samples, it was counteracted by ADE in the presence of FcγR or C1q. Considering the ubiquity of C1q and its cellular receptors, C1q-mediated ADE may more likely occur in respiratory epithelial cells, which SARS-CoV-2 primarily infects. Our data highlight the importance of careful monitoring of the antibody properties in COVID-19 convalescent and vaccinated individuals.

The Epidemiological, Clinical Features and Outcomes of Imported Chinese COVID-19 Patients Following Inactivated Vaccines Injection

Background

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccination had been demonstrated as an effective way to reduce the risk of coronavirus disease 2019 (COVID-19), and only a few vaccines suffered from SARS-CoV-2 infection. However, limited data concerning the clinical features of these vaccines infected with SARS-CoV-2 can be identified.

Methods

We retrospectively collected and analyzed epidemiological and clinical characteristics data of the imported COVID-19 cases who received Chinese inactivated vaccines abroad. Data were extracted from electronic medical records from a designated hospital in the Shaanxi Province of China between March 22 and May 17, 2021.

Results

Totally, 46 confirmed SARS-CoV-2 infection patients were enrolled. The mean age was 40.5 years (range 20–61), 41 (89.1%) are male. Eighteen (39.1%) patients were from Pakistan. Fourteen (30.4%) patients had at least one comorbidity. Forty (87.0%) and 6 cases were fully vaccinated and partly vaccinated. The time interval between vaccination and infection was 88 days (IQR, 33–123), 31 (67.4%) and 15 (32.6%) were asymptomatic and symptomatic cases, respectively. Fever (3/46, 6.5%) was the most common symptom; however, none had a body temperature higher than 38.0°C, and no severe case was observed. Notably, the rate of SARS-CoV-2 shedding discontinuation at 7 days after hospitalization in asymptomatic cases was higher than symptomatic one (93.5% vs 40%, P < 0.0001).

Conclusion

Individuals who received Chinese inactivated vaccines abroad remain to have the probability of being infected with SARS-CoV-2, but all the vaccines infected with SARS-CoV-2 were asymptomatic or had mild symptoms with favorable clinical outcomes.

Quantity of IgG response to SARS-CoV-2 spike glycoprotein predicts pulmonary recovery from COVID-19

The CovILD study is a prospective, multicenter, observational cohort study to systematically follow up patients after coronavirus disease-2019 (COVID-19). We extensively evaluated 145 COVID-19 patients at 3 follow-up visits scheduled for 60, 100, and 180 days after initial confirmed diagnosis based on typical symptoms and a positive reverse transcription-polymerase chain reaction (RT-PCR) for severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2). We employed comprehensive pulmonary function and laboratory tests, including serum concentrations of IgG against the viral spike (S) glycoprotein, and compared the results to clinical data and chest computed tomography (CT). We found that at the 60 day follow-up, 131 of 145 (90.3%) participants displayed S-specific serum IgG levels above the cut-off threshold. Notably, the highly elevated IgG levels against S glycoprotein positively correlated with biomarkers of immune activation and negatively correlated with pulmonary function and the extent of pulmonary CT abnormalities. Based on the association between serum S glycoprotein-specific IgG and clinical outcome, we generated an S-specific IgG-based recovery score that, when applied in the early convalescent phase, accurately predicted delayed pulmonary recovery after COVID-19. Therefore, we propose that S-specific IgG levels serve as a useful immunological surrogate marker for identifying at-risk individuals with persistent pulmonary injury who may require intensive follow-up care after COVID-19.

Humoral and Cellular Responses to SARS-CoV-2 in Convalescent COVID-19 Patients With Multiple Sclerosis

Background and Objectives

Information about humoral and cellular responses to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and antibody persistence in convalescent (COVID-19) patients with multiple sclerosis (PwMS) is scarce. The objectives of this study were to investigate factors influencing humoral and cellular responses to SARS-CoV-2 and its persistence in convalescent COVID-19 PwMS.

Methods

This is a retrospective study of confirmed COVID-19 convalescent PwMS identified between February 2020 and May 2021 by SARS-CoV-2 antibody testing. We examined relationships between demographics, MS characteristics, disease-modifying therapy (DMT), and humoral (immunoglobulin G against spike and nucleocapsid proteins) and cellular (interferon-gamma [IFN-γ]) responses to SARS-CoV-2.

Results

A total of 121 (83.45%) of 145 PwMS were seropositive, and 25/42 (59.5%) presented a cellular response up to 13.1 months after COVID-19. Anti–CD20-treated patients had lower antibody titers than those under other DMTs (p < 0.001), but severe COVID-19 and a longer time from last infusion increased the likelihood of producing a humoral response. IFN-γ levels did not differ among DMT. Five of 7 (71.4%) anti-–CD20-treated seronegative patients had a cellular response. The humoral response persisted for more than 6 months in 41/56(81.13%) PwMS. In multivariate analysis, seropositivity decreased due to anti-CD20 therapy (OR 0.08 [95% CI 0.01–0.55]) and increased in males (OR 3.59 [1.02–12.68]), whereas the cellular response decreased in those with progressive disease (OR 0.04 [0.001–0.88]). No factors were associated with antibody persistence.

Discussion

Humoral and cellular responses to SARS-CoV-2 are present in COVID-19 convalescent PwMS up to 13.10 months after COVID-19. The humoral response decreases under anti-CD20 treatment, although the cellular response can be detected in anti–CD20-treated patients, even in the absence of antibodies.

SARS-CoV-2 antibody and T cell responses one year after COVID-19 and the booster effect of vaccination: A prospective cohort study

OBJECTIVES

First, to describe SARS-CoV-2 T cell and antibody responses in a prospective cohort of healthcare workers that suffered from mild to moderate COVID-19 approximately one year ago. Second, to assess COVID-19 vaccine-induced immune responses in these prior-infected individuals.

METHODS

SARS-CoV-2-specific T cell and anti-SARS-CoV-2-Spike-RBD immunoglobulin G (IgG) responses in blood were determined before COVID-19 vaccination with mRNA-1273, BNT162b2, Ad26.CoV2-S or ChAdOx1-S, two weeks after first vaccination, and after second vaccination.

RESULTS

55 prior SARS-CoV-2 infected and seroconverted individuals were included. S1-specific T cell responses and anti-RBD IgG were detectable one year post SARS-CoV-2 infection: 24 spot-forming cells per 10⁶ peripheral blood mononuclear cells (SFCs/10⁶ PBMCs) after S1 stimulation and anti-RBD IgG concentration of 74 (IQR 36-158) IU/mL. Responses after the first and second vaccination were comparable with S1-specfic T cell responses of 198 (IQR 137-359) and 180 (IQR 103-347) SFCs/10⁶ PBMCs, and IgG concentrations of 6792 (IQR 3386-15,180) and 6326 (IQR 2336-13,440) IU/mL, respectively. These responses retained up to four months after vaccination.

CONCLUSIONS

Both T cell and IgG responses against SARS-CoV-2 persist for up to one year after COVID-19. A second COVID-19 vaccination in prior-infected individuals did not further increase immune responses in comparison to one vaccination.

Prevalence and incidence of antibodies against SARS-CoV-2 among primary healthcare providers in Belgium during 1 year of the COVID-19 epidemic: prospective cohort study protocol

INTRODUCTION

National SARS-CoV-2 seroprevalence data provide essential information about population exposure to the virus and help predict the future course of the epidemic. Early cohort studies have suggested declines in levels of antibodies in individuals associated with, for example, illness severity, age and comorbidities. This protocol focuses on the seroprevalence among primary healthcare providers (PHCPs) in Belgium. PHCPs manage the vast majority of (COVID-19) patients and therefore play an essential role in the efficient organisation of healthcare. Currently, evidence is lacking on (1) how many PHCPs get infected with SARS-CoV-2 in Belgium, (2) the rate at which this happens, (3) their clinical spectrum, (4) their risk factors, (5) the effectiveness of the measures to prevent infection and (6) the accuracy of the serology-based point-of-care test (POCT) in a primary care setting.

METHODS AND ANALYSIS

This study will be set up as a prospective cohort study. General practitioners (GPs) and other PHCPs (working in a GP practice) will be recruited via professional networks and professional media outlets to register online to participate. Registered GPs and other PHCPs will be asked at each testing point (n=9) to perform a capillary blood sample antibody POCT targeting IgM and IgG against the receptor-binding domain of SARS-CoV-2 and complete an online questionnaire. The primary outcomes are the prevalence and incidence of antibodies against SARS-CoV-2 in PHCPs during a 12-month follow-up period. Secondary outcomes include the longevity of antibodies against SARS-CoV-2.

ETHICS AND DISSEMINATION

Ethical approval has been granted by the ethics committee of the University Hospital of Antwerp/University of Antwerp (Belgian registration number: 3002020000237). Alongside journal publications, dissemination activities include the publication of monthly reports to be shared with the participants and the general population through the publicly available website of the Belgian health authorities (Sciensano).

TRIAL REGISTRATION NUMBER

NCT04779424.

Is the BCG Vaccine an Answer to Future Pandemic Preparedness?

While the development of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccines was rapid, time to development and implementation challenges remain that may impact the response to future pandemics. Trained immunity via bacille Calmette-Guerin (BCG) vaccination (an antigen agnostic strategy) offers a potential intervention against future novel pathogens via an existing, safe, and widely distributed vaccine to protect vulnerable populations and preserve health system capacity while targeted vaccines are developed and implemented.

Persistence of Antibodies Against Spike Glycoprotein of SARS-CoV-2 in Healthcare Workers Post Double Dose of BBV-152 and AZD1222 Vaccines

Purpose: We investigated the persistence of the vaccine-induced immunoglobulin G (IgG) antibodies against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) among healthcare workers (HCWs) in Odisha who received a complete dose of either Covaxin or Covishield vaccine.

Methods: This 24-week longitudinal cohort study was conducted from January to July 2021 with participants from 6 healthcare and research facilities of Odisha to understand the dynamicity of the vaccine-induced IgG antibodies against SARS-CoV-2 after the complete dose of vaccines.

Results: Serum samples were collected from 614 participants during each follow-up and were tested in two chemiluminescent microparticle immunoassay (CLIA)-based platforms to detect SARS-CoV-2 antibodies both qualitatively and quantitatively. Among these participants, 308 (50.2%) participants were Covishield recipients and the rest 306 (49.8%) participants took Covaxin. A total of 81 breakthrough cases were recorded and the rest 533 HCWs without any history of postvaccination infection showed significant antibody waning either from T3 (Covaxin recipient) or T4 (Covishield recipient). The production of vaccine-induced IgG antibodies is significantly higher (p < 0.001) in Covishield compared with Covaxin. Covishield recipients produced higher median anti-S IgG titer than Covaxin. No statistically significant differences in antibody titers were observed based on age, gender, comorbidities, and blood groups.

Conclusion: This 6-month follow-up study documents a 2-fold and 4-fold decrease in spike antibody titer among Covishield and Covaxin recipients, respectively. The clinical implications of antibody waning after vaccination are not well understood. It also highlights the need for further data to understand the long-term persistence of vaccine-induced antibody and threshold antibody titer required for protection against reinfection.

Evaluation of Clinical and Immune Responses in Recovered Children with Mild COVID-19

The coronavirus disease 2019 (COVID-19) has spread globally and variants continue to emerge, with children are accounting for a growing share of COVID-19 cases. However, the establishment of immune memory and the long-term health consequences in asymptomatic or mildly symptomatic children after severe acute respiratory syndrome coronavirus 2 infection are not fully understood. We collected clinical data and whole blood samples from discharged children for 6–8 months after symptom onset among 0-to-14-year-old children. Representative inflammation signs returned to normal in all age ranges. The infants and young children (0–4 years old) had lung lesions that persisted for 6–8 months and were less responsive for antigen-specific IgG secretion. In the 5-to-14-year-old group, lung imaging abnormalities gradually recovered, and the IgG-specific antibody response was strongest. In addition, we found a robust IgM⁺ memory B cell response in all age. Memory T cells specific for the spike or nucleocapsid protein were generated, with no significant difference in IFN-γ response among all ages. Our study highlights that although lung lesions caused by COVID-19 can last for at least 6–8 months in infants and young children, most children have detectable residual neutralizing antibodies and specific cellular immune responses at this stage.

A Highly Sensitive and Specific SARS-CoV-2 Spike- and Nucleoprotein-Based Fluorescent Multiplex Immunoassay (FMIA) to Measure IgG, IgA, and IgM Class Antibodies

Validation and standardization of accurate serological assays are crucial for the surveillance of the coronavirus disease 2019 (COVID-19) pandemic and population immunity. We describe the analytical and clinical performance of an in-house fluorescent multiplex immunoassay (FMIA) for simultaneous quantification of antibodies against the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) nucleoprotein and spike glycoprotein. Furthermore, we calibrated IgG-FMIA against World Health Organization (WHO) International Standard and compared FMIA results to an in-house enzyme immunoassay (EIA) and a microneutralization test (MNT). We also compared the MNT results of two laboratories. IgG-FMIA displayed 100% specificity and sensitivity for samples collected 13 to 150 days post-onset of symptoms (DPO). For IgA- and IgM-FMIA, 100% specificity and sensitivity were obtained for a shorter time window (13 to 36 and 13 to 28 DPO for IgA- and IgM-FMIA, respectively). FMIA and EIA results displayed moderate to strong correlation, but FMIA was overall more specific and sensitive. IgG-FMIA identified 100% of samples with neutralizing antibodies (NAbs). Anti-spike IgG concentrations correlated strongly (ρ = 0.77 to 0.84, P < 2.2 × 10-16) with NAb titers, and the two laboratories' NAb titers displayed a very strong correlation (ρ = 0.95, P < 2.2 × 10-16). Our results indicate good correlation and concordance of antibody concentrations measured with different types of in-house SARS-CoV-2 antibody assays. Calibration against the WHO international standard did not, however, improve the comparability of FMIA and EIA results. IMPORTANCE SARS-CoV-2 serological assays with excellent clinical performance are essential for reliable estimation of the persistence of immunity after infection or vaccination. In this paper we present a thoroughly validated SARS-CoV-2 serological assay with excellent clinical performance and good comparability to neutralizing antibody titers. Neutralization tests are still considered the gold standard for SARS-CoV-2 serological assays, but our assay can identify samples with neutralizing antibodies with 100% sensitivity and 96% specificity without the need for laborious and slow biosafety level 3 (BSL-3) facility-requiring analyses.

Persistence of Robust Humoral Immune Response in Coronavirus Disease 2019 Convalescent Individuals Over 12 Months After Infection

Background

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection elicits varying degrees of protective immunity conferred by neutralizing antibodies (nAbs). In this study, we report the persistence of nAb responses over 12 months after infection despite their decreasing trend noticed from 6 months.

Methods

The study included sera from 497 individuals who had been infected with SARS-CoV-2 between January and August 2020. Samples were collected at 6 and 12 months after onset. The titers of immunoglobulin (Ig)G to the viral nucleocapsid protein (NP) and receptor-binding domain (RBD) of the spike protein were measured by chemiluminescence enzyme immunoassay. The nAb titer was determined using lentivirus-based pseudovirus or authentic virus.

Results

Antibody titers of NP-IgG, RBD-IgG, and nAbs were higher in severe and moderate cases than in mild cases at 12 months after onset. Although the nAb levels were likely to confer adequate protection against wild-type viral infection, the neutralization activity to recently circulating variants in some of the mild cases (~30%) was undermined, implying the susceptibility to reinfection with the variants of concerns (VOCs).

Conclusions

Coronavirus disease 2019 convalescent individuals have robust humoral immunity even at 12 months after infection albeit that the medical history and background of patients could affect the function and dynamics of antibody response to the VOCs.

SARS-CoV-2 Specific IgG Antibodies Persist Over a 12-Month Period in Oral Mucosal Fluid Collected From Previously Infected Individuals

Background

Developing an understanding of the antibody response, seroprevalence, and seroconversion from natural infection and vaccination against SARS-CoV-2 will give way to a critical epidemiological tool to predict reinfection rates, identify vulnerable communities, and manage future viral outbreaks. To monitor the antibody response on a larger scale, we need an inexpensive, less invasive, and high throughput method.

Methods

Here we investigate the use of oral mucosal fluids from individuals recovered from SARS-CoV-2 infection to monitor antibody response and persistence over a 12-month period. For this cohort study, enzyme-linked immunosorbent assays (ELISAs) were used to quantify anti-Spike(S) protein IgG antibodies in participants who had prior SARS-CoV-2 infection and regularly (every 2-4 weeks) provided both serum and oral fluid mucosal fluid samples for longitudinal antibody titer analysis.

Results

In our study cohort (n=42) with 17 males and 25 females with an average age of 45.6 +/- 19.3 years, we observed no significant change in oral mucosal fluid IgG levels across the time course of antibody monitoring. In oral mucosal fluids, all the participants who initially had detectable antibodies continued to have detectable antibodies throughout the study.

Conclusions

Based on the results presented here, we have shown that oral mucosal fluid-based assays are an effective, less invasive tool for monitoring seroprevalence and seroconversion, which offers an alternative to serum-based assays for understanding the protective ability conferred by the adaptive immune response from viral infection and vaccination against future reinfections.

Does infection with or vaccination against SARS-CoV-2 lead to lasting immunity?

Many nations are pursuing the rollout of SARS-CoV-2 vaccines as an exit strategy from unprecedented COVID-19-related restrictions. However, the success of this strategy relies critically on the duration of protective immunity resulting from both natural infection and vaccination. SARS-CoV-2 infection elicits an adaptive immune response against a large breadth of viral epitopes, although the duration of the response varies with age and disease severity. Current evidence from case studies and large observational studies suggests that, consistent with research on other common respiratory viruses, a protective immunological response lasts for approximately 5-12 months from primary infection, with reinfection being more likely given an insufficiently robust primary humoral response. Markers of humoral and cell-mediated immune memory can persist over many months, and might help to mitigate against severe disease upon reinfection. Emerging data, including evidence of breakthrough infections, suggest that vaccine effectiveness might be reduced significantly against emerging variants of concern, and hence secondary vaccines will need to be developed to maintain population-level protective immunity. Nonetheless, other interventions will also be required, with further outbreaks likely to occur due to antigenic drift, selective pressures for novel variants, and global population mobility.

Long-term specific IgG response to SARS-CoV-2 nucleocapsid protein in recovered COVID-19 patients

This study monitored the long-term immune response to severe acute respiratory syndrome coronavirus (SARS-CoV)-2 infection in patients who had recovered from coronavirus disease (COVID)-19. Anti-nucleocapsid immunoglobulin G (anti-N IgG) titer in serum samples collected at a single (N = 302) or multiple time points (N = 229) 3–12 months after COVID-19 symptom onset or SARS-CoV-2 detection in respiratory specimens was measured by semiquantitative chemiluminescent microparticle immunoassay. The 531 patients (966 specimens) were classified according to the presence or absence of pneumonia symptoms. Anti N IgG was detected in 87.5% of patients (328/375) at 3 months, 38.6% (93/241) at 6 months, 23.7% (49/207) at 9 months, and 26.6% (38/143) at 12 months. The anti-N IgG seropositivity rate was significantly lower at 6, 9, and 12 months than at 3 months (P < 0.01) and was higher in the pneumonia group than in the non-pneumonia/asymptomatic group at 6 months (P < 0.01), 9 months (P = 0.04), and 12 months (P = 0.04). The rate started to decline 6–12 months after symptom onset. Anti-N IgG sample/cutoff index was positively correlated with age (r = 0.192, P < 0.01) but negatively correlated with interval between symptom onset and blood sampling (r =  − 0.567, P < 0.01). These findings can guide vaccine strategies in recovered COVID-19 patients.

Long-Lasting Immunity Against SARS-CoV-2: Dream or Reality?

Since its declaration as a pandemic in March 2020, SARS-CoV-2 has infected more than 217 million people worldwide and despite mild disease in the majority of the cases, more than 4.5 million cases of COVID-19-associated death have been reported as of September 2021. The question whether recovery from COVID-19 results in prevention of reinfection can be answered with a "no" since cases of reinfections have been reported. The more important question is whether during SARS-CoV-2 infection, a protective immunity is built and maintained afterwards in a way which protects from possibly severe courses of disease in case of a reinfection. A similar question arises with respect to vaccination: as of September 2021, globally, more than 5.2 billion doses of vaccines have been administered. Therefore, it is of utmost importance to study the cellular and humoral immunity toward SARS-CoV-2 in a longitudinal manner. In this study, reconvalescent COVID-19 patients have been followed up for more than 1 year after SARS-CoV-2 infection to characterize in detail the long-term humoral as well as cellular immunity. Both SARS-CoV-2-specific T cells and antibodies could be detected for a period of more than 1 year after infection, indicating that the immune protection established during initial infection is maintained and might possibly protect from severe disease in case of reinfection or infection with novel emerging variants. Moreover, these data demonstrate the opportunity for immunotherapy of hospitalized COVID-19 patients via adoptive transfer of functional antiviral T cells isolated from reconvalescent individuals.

COVID-19 reinfection: the role of natural immunity, vaccines, and variants

The COVID-19 pandemic has altered innumerable lives. Although recent mass vaccinations offer a glimmer of hope, the rising death toll and new variants continue to dominate the current scenario. As we begin to understand more about SARS-CoV-2 infections, the territory of reinfections with COVID-19 remains unexplored. In this review, we will discuss several aspects of reinfection: (a) How is COVID-19 reinfection characterized? (b) Does prior literature differentiate between reinfection and reactivation? (c) What SARS-CoV-2 strains do the vaccines target and can they protect against new strains? Larger and longer timeline studies are needed to understand reinfection risks. With the ongoing distribution of the SARS-CoV-2 vaccines to provide protection, the understanding of the possibility for SARS-CoV-2 reinfection remains critical.

Abbreviations CDC: Centers for Disease ControlSARS-CoV-2: Severe acute respiratory syndrome coronavirus 2COVID-19: Coronavirus disease 2019RT-PCR: Reverse Transcription Polymerase Chain ReactionPASC: Post-Acute Sequelae of SARS-CoV-2 infection

SARS-CoV-2-specific T-cell responses after COVID-19 recovery in patients with rheumatic diseases on immunosuppressive therapy

Background

In patients with immune-mediated rheumatic diseases (RMD), the development of T-cell responses against SARS-CoV-2 may be impaired by either the immune disturbances associated with the disease, or by the effects of immunosuppressive therapies. We aimed at determining the magnitude of SARS-CoV-2-specific interferon (IFN)-γ-producing T-cell response after COVID-19 recovery in a cohort of patients with RMD on different immunosuppressive therapies.

Patients and methods

53 adult patients with inflammatory or autoimmune RMD and 61 sex and age-matched non-RMD patients with confirmed COVID-19 were included. Peripheral blood mononuclear cells were obtained and T-cell-IFN-γ antigen-specific responses against the S1 domain of the spike glycoprotein, the nucleoprotein (N) and the membrane (M) protein from SARS-CoV-2 were assessed by FluoroSpot assay.

Results

Patients with RMD and COVID-19 showed positive T-cells-IFN-γ responses to SARS-COV-2 antigens, in a similar proportion and magnitude as non-RMD patients at a median of 298 [151–316] and 165 [162–167] days after COVID-19 respectively. Among RMD patients 83%, 87% and 90%, and among non-RMD patients, 95%, 87% and 93% responded to S1, N and M protein respectively. Similar responses were observed in the different diagnostic and therapeutic groups, including conventional synthetic disease-modifying anti-rheumatic drugs (csDMARDs), TNF-α inhibitors, IL-17 inhibitors, rituximab, JAK inhibitors or other immunosuppressants.

Conclusion

T-cell responses to the main SARS-CoV-2 antigens are present after COVID-19 recovery in most patients with RMD and are not impaired by immunosuppressive therapies.

Profiling Antibody Response Patterns in COVID-19: Spike S1-Reactive IgA Signature in the Evolution of SARS-CoV-2 Infection

This contribution explores in a new statistical perspective the antibody responses to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in 141 coronavirus disease 2019 (COVID-19) patients exhibiting a broad range of clinical manifestations. This cohort accurately reflects the characteristics of the first wave of the SARS-CoV-2 pandemic in Italy. We determined the IgM, IgA, and IgG levels towards SARS-CoV-2 S1, S2, and NP antigens, evaluating their neutralizing activity and relationship with clinical signatures. Moreover, we longitudinally followed 72 patients up to 9 months postsymptoms onset to study the persistence of the levels of antibodies. Our results showed that the majority of COVID-19 patients developed an early virus-specific antibody response. The magnitude and the neutralizing properties of the response were heterogeneous regardless of the severity of the disease. Antibody levels dropped over time, even though spike reactive IgG and IgA were still detectable up to 9 months. Early baseline antibody levels were key drivers of the subsequent antibody production and the long-lasting protection against SARS-CoV-2. Importantly, we identified anti-S1 IgA as a good surrogate marker to predict the clinical course of COVID-19. Characterizing the antibody response after SARS-CoV-2 infection is relevant for the early clinical management of patients as soon as they are diagnosed and for implementing the current vaccination strategies.

[Coronavirus disease 2019 in childhood and adolescence]

The coronavirus disease 2019 (COVID‑19) mostly occurs in children and adolescents as an asymptomatic infection. The course of the disease is usually mild or moderate. The estimated seroprevalence in Germany before the start of the vaccination program in children and adolescents was > 10%. Individual risk factors for a severe course are known. The COVID‑19-associated pediatric inflammatory multisystem syndrome (PIMS) is a very rare and severe disease with a favorable prognosis if diagnosed early and treated appropriately. The data situation on long-COVID syndrome in children and adolescents is still insufficiently defined and the incidence is not known. The primary source of infections in children and adolescents are household contacts. Transmission in school settings and other day care facilities play a subordinate role, at least in Germany.Two mRNA vaccines are currently approved in Europe for the prevention of COVID‑19 in children and adolescents above the age of 12 years. Except for the very rare occurrence of pericarditis/myocarditis in temporal association with the vaccination, especially in young men, the COVID‑19 vaccines are considered effective and safe in the age group 12-17 years. The Standing Vaccination Commission (STIKO) issued a vaccination recommendation for all 12-17-year-olds on 19 August 2021.

Robust Neutralizing Antibody Levels Detected after Either SARS-CoV-2 Vaccination or One Year after Infection

Humoral immunity after infection or after vaccination against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has been attributed a key part in mitigating the further transmission of the virus. In this study, we used a commercial anti-Spike immunoglobulin G (S-IgG) assay and developed a cell culture-based neutralization assay to understand the longitudinal course of neutralizing antibodies in both SARS-CoV2 infected or vaccinated individuals. We show that even more than one year after infection, about 78% of observed study participants remained seropositive concerning S-IgG antibodies. In addition, the serum of the individuals had stable neutralization capacity in a neutralization assay against a SARS-CoV-2 patient isolate from March 2020. We also examined volunteers after either homologous BNT162b2 prime-boost vaccination or heterologous AZD1222 prime/mRNA-based booster vaccination. Both the heterologous and the homologous vaccination regimens induced higher levels of neutralizing antibodies in healthy subjects when compared to subjects after a mild infection, showing the high effectiveness of available vaccines. In addition, we could demonstrate the reliability of S-IgG levels in predicting neutralization capacity, with 94.8% of seropositive samples showing a neutralization titer of ≥10, making it a viable yet cheap and easy-to-determine surrogate parameter for neutralization capacity.

Persistence of neutralizing antibodies a year after SARS-CoV-2 infection in humans

Most subjects develop antibodies to SARS‐CoV‐2 following infection. In order to estimate the duration of immunity induced by SARS‐CoV‐2 it is important to understand for how long antibodies persist after infection in humans. Here, we assessed the persistence of serum antibodies following WT SARS‐CoV‐2 infection at 8 and 13 months after diagnosis in 367 individuals. The SARS‐CoV‐2 spike IgG (S‐IgG) and nucleoprotein IgG (N‐IgG) concentrations and the proportion of subjects with neutralizing antibodies (NAb) were assessed. Moreover, the NAb titers among a smaller subset of participants (n = 78) against a WT virus (B) and variants of concern (VOCs): Alpha (B.1.1.7), Beta (B.1.351), and Delta (B.1.617.2) were determined. We found that NAb against the WT virus persisted in 89% and S‐IgG in 97% of subjects for at least 13 months after infection. Only 36% had N‐IgG by 13 months. The mean S‐IgG concentrations declined from 8 to 13 months by less than one third; N‐IgG concentrations declined by two‐thirds. Subjects with severe infection had markedly higher IgG and NAb levels and are expected to remain seropositive for longer. Significantly lower NAb titers against the variants compared to the WT virus, especially after a mild disease, suggests reduced protection against VOCs.

Antibody-dependent cellular cytotoxicity response to SARS-CoV-2 in COVID-19 patients

Antibody-dependent cellular cytotoxicity (ADCC) responses to viral infection are a form of antibody regulated immune responses mediated through the Fc fragment. Whether severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) triggered ADCC responses contributes to COVID-19 disease development is currently not well understood. To understand the potential correlation between ADCC responses and COVID-19 disease development, we analyzed the ADCC activity and neutralizing antibody response in 255 individuals ranging from asymptomatic to fatal infections over 1 year post disease. ADCC was elicited by 10 days post-infection, peaked by 11-20 days, and remained detectable until 400 days post-infection. In general, patients with severe disease had higher ADCC activities. Notably, patients who had severe disease and recovered had higher ADCC activities than patients who had severe disease and deceased. Importantly, ADCC activities were mediated by a diversity of epitopes in SARS-COV-2-infected mice and induced to comparable levels against SARS-CoV-2 variants of concern (VOCs) (B.1.1.7, B.1.351, and P.1) as that against the D614G mutant in human patients and vaccinated mice. Our study indicates anti-SARS-CoV-2 ADCC as a major trait of COVID-19 patients with various conditions, which can be applied to estimate the extra-neutralization level against COVID-19, especially lethal COVID-19.

Antibody Responses to Natural SARS-CoV-2 Infection or after COVID-19 Vaccination

The novel coronavirus, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), is the causative agent of the ongoing pandemic of coronavirus disease 2019 (COVID-19). The clinical severity of COVID-19 ranges from asymptomatic to critical disease and, eventually, death in smaller subsets of patients. The first case of COVID-19 was declared at the end of 2019 and it has since spread worldwide and remained a challenge in 2021, with the emergence of variants of concern. In fact, new concerns were the still unclear situation of SARS-CoV-2 immunity during the ongoing pandemic and progress with vaccination. If maintained at sufficiently high levels, the immune response could effectively block reinfection, which might confer long-lived protection. Understanding the protective capacity and the duration of humoral immunity during SARS-CoV-2 infection or after vaccination is critical for managing the pandemic and would also provide more evidence about the efficacy of SARS-CoV-2 vaccines. However, the exact features of antibody responses that govern SARS-CoV-2 infection or after vaccination remain unclear. This review summarizes the main knowledge that we have about the humoral immune response during COVID-19 disease or after vaccination. Such knowledge should help to optimize vaccination strategies and public health decisions.

Long-term SARS-CoV-2-specific immune and inflammatory responses in individuals recovering from COVID-19 with and without post-acute symptoms

We describe severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)-specific T cell responses, soluble markers of inflammation, and antibody levels and neutralization capacity longitudinally in 70 individuals with PCR-confirmed SARS-CoV-2 infection. Participants represent a spectrum of illness and recovery, including some with persistent viral shedding in saliva and many experiencing post-acute sequelae of SARS-CoV-2 infection (PASC). T cell responses remain stable for up to 9 months. Whereas the magnitude of early CD4⁺ T cell immune responses correlates with severity of initial infection, pre-existing lung disease is independently associated with higher long-term SARS-CoV-2-specific CD8⁺ T cell responses. Among participants with PASC 4 months following coronavirus disease 2019 (COVID-19) symptom onset, we observe a lower frequency of CD8⁺ T cells expressing CD107a, a marker of degranulation, in response to Nucleocapsid (N) peptide pool stimulation, and a more rapid decline in the frequency of N-specific interferon-γ-producing CD8⁺ T cells. Neutralizing antibody levels strongly correlate with SARS-CoV-2-specific CD4⁺ T cell responses.

Affinity Tag Coating Enables Reliable Detection of Antigen-Specific B Cells in Immunospot Assays

Assessment of humoral immunity to SARS-CoV-2 and other infectious agents is typically restricted to detecting antigen-specific antibodies in the serum. Rarely does immune monitoring entail assessment of the memory B-cell compartment itself, although it is these cells that engage in secondary antibody responses capable of mediating immune protection when pre-existing antibodies fail to prevent re-infection. There are few techniques that are capable of detecting rare antigen-specific B cells while also providing information regarding their relative abundance, class/subclass usage and functional affinity. In theory, the ELISPOT/FluoroSpot (collectively ImmunoSpot) assay platform is ideally suited for antigen-specific B-cell assessments since it provides this information at single-cell resolution for individual antibody-secreting cells (ASC). Here, we tested the hypothesis that antigen-coating efficiency could be universally improved across a diverse set of viral antigens if the standard direct (non-specific, low affinity) antigen absorption to the membrane was substituted by high-affinity capture. Specifically, we report an enhancement in assay sensitivity and a reduction in required protein concentrations through the capture of recombinant proteins via their encoded hexahistidine (6XHis) affinity tag. Affinity tag antigen coating enabled detection of SARS-CoV-2 Spike receptor binding domain (RBD)-reactive ASC, and also significantly improved assay performance using additional control antigens. Collectively, establishment of a universal antigen-coating approach streamlines characterization of the memory B-cell compartment after SARS-CoV-2 infection or COVID-19 vaccinations, and facilitates high-throughput immune-monitoring efforts of large donor cohorts in general.