Safety and immunogenicity of seven COVID-19 vaccines as a third dose (booster) following two doses of ChAdOx1 nCov-19 or BNT162b2 in the UK (COV-BOOST): a blinded, multicentre, randomised, controlled, phase 2 trial

Evaluation of humoral and cellular immune responses in healthcare workers with varying levels of SARS-CoV-2 exposure: effects of CoronaVac vaccination followed by heterologous booster

Background

The COVID-19 pandemic demanded diverse vaccination strategies, and there is significant interest in their effectiveness in generating a robust immune response. In Brazil, the use of CoronaVac was crucial in reducing mortality; however, heterologous booster doses were necessary to enhance memory immune response. This study aimed to evaluate the humoral and cellular immunity in healthcare workers who were vaccinated with a complete regimen of CoronaVac and subsequently received heterologous booster doses over nearly one year.

Methods

A longitudinal study recruited healthcare professionals with varying levels of exposure to SARS-CoV-2 from the Health Complex of the Rio de Janeiro State University (UERJ), Rio de Janeiro, Brazil. Blood samples were collected at five time points, including baseline and after vaccination with CoronaVac and heterologous booster doses (ChAdOx1 nCov-19 or BNT162b2). The Th1/Th2/Th17 cytokine production was measured by Flow Cytometry, using whole blood samples stimulated or not with the SARS-CoV-2 Spike protein. In parallel, serum levels of IgG antibodies against Spike (anti-S) and Nucleocapsid (anti-N) proteins were assessed using an immunoassay. Adjustments were made for confounding factors, including age, sex, level of SARS-CoV-2 exposure, and COVID-19 infection status.

Results

Our results demonstrate that CoronaVac induced high anti-S IgG levels at all evaluated time points (P<0.01). Cytokine analysis revealed a sustained production of antigen-specific Th1 cytokines, including IL-2 (P<0.01) and IFN-γ (P<0.05) regardless of level of SARS-CoV-2 exposure or previous COVID-19 infection at any point during the study. Additionally, we identified six moderate to strong positive correlations (P<0.0001): IL-10 and IFN-γ (ρ=0.77), IL-6 and TNF (ρ=0.77), IL-2 and IFN-γ (ρ=0.71), IL-6 and IL-10 (ρ=0.66), anti-N IgG and anti-S IgG (ρ=0.62), and IL-2 and anti-S IgG (ρ=0.62).

Conclusion

The CoronaVac elicited an antigen-specific cellular immune response, characterized by enhancing the production of key cytokines such as IFN-γ and IL-2, with high levels of anti-S IgG. Furthermore, the administration of heterologous boosters significantly enhanced these immune responses, demonstrating induced-specific immunological response. These findings underscore the importance of primary vaccination and boosters in inducing immune protection against COVID-19, potentially informing future vaccination policies and approaches.

An open-label study on the safety and immunogenicity of a PD-1-enhanced DNA vaccine used as a T cell booster for COVID-19

BACKGROUND

Inducing T cell responses by vaccines among elderly has been a long-standing challenge. There is a need for effective COVID-19 vaccines to boost waning immunity against emerging SARS-CoV-2 variants, especially for the elderly. This study investigated the safety and immunogenicity of a PD-1-enhanced COVID-19 DNA vaccine (ICCOV™), as a booster vaccine in healthy adults (aged 18-59 years) and elderly (aged 60-75 years).

METHODS

This open-label, non-randomised Phase 2 study enrolled healthy participants aged 18-75 years who had previously been vaccinated with Sinovac CoronaVac, Pfizer-bioNTech Comirnaty vaccines, or both. Participants were stratified into four cohorts according to age, primary vaccination, and COVID-19 infection history, namely Adult-CoronaVac, Adult-Comirnaty, Adult-Mixed, and Elderly-Mixed cohorts. Participants were administered with a single dose of 2 mg ICCOV intramuscularly followed by electroporation using the proprietary TERESA-EPT-I device. Participants were followed up for 60 days. The primary endpoint was T cell immunogenicity within 28 days post-ICCOV vaccination. The secondary endpoints were safety, T cell and antibody responses within 60 days post-vaccination (ClinicalTrials.govNCT05904054).

FINDINGS

The study was conducted at Gleneagles Hospital Hong Kong between 30 June and 30 November 2023. In total, 31 participants were enrolled across the Adult-Comirnaty (n = 4), Adult-Mixed (n = 15), and Elderly-Mixed (n = 12) cohorts. All enrolled participants completed the study and were included in safety and immunogenicity analyses. Among these participants, 2 from the Adult-Comirnaty cohort, 9 from the Adult-Mixed cohort, and 4 from the Elderly-Mixed cohort reported a total of 31 adverse events, all in grade 1-2. Pain at the administration site was the most frequently reported (38·7%). The proportion of participants demonstrating an increase of SARS-CoV-2-specific ELISpot T cell responses within 28 days post ICCOV vaccination was 100% (4/4), 80% (12/15), and 75% (9/12) in Adult-Comirnaty, Adult-Mixed, and Elderly-Mixed cohorts, respectively. Single ICCOV vaccination elicited SARS-CoV-2-specific, polyfunctional CD8+ and CD4+ T cells against both ancestral and Omicron strains in all cohorts. The magnitude of responses was not inferior in the elderly, compared to adults. No elevation of antibody responses was detected.

INTERPRETATION

Single PD-1-enhanced ICCOV booster DNA vaccination did not show major safety concerns. The ICCOV booster elicited cross-reactive T cell responses to multiple SARS-CoV-2 strains, including in the elderly. This report demonstrates the T-cell boosting immunogenicity of ICCOV in the susceptible elderly population.

FUNDING

Clinical Translational Catalyst, Hong Kong Science & Technology Parks Corporation.

What is the quality of evidence informing vaccine clinical practice recommendations in Australia?

BACKGROUND

Vaccine policy and guideline recommendations require high quality evidence. A review of the evidence quality used to inform vaccine clinical practice guidelines could help guide researchers on how to improve the design of their clinical studies to produce evidence of greater value to decision-makers. In Australia, the Australian Technical Advisory Group on Immunisation (ATAGI) develops evidence-based vaccine clinical practice recommendations using the Grading of Recommendations Assessment, Development and Evaluation (GRADE) methodology, a transparent, systematic and methodical framework for developing and presenting summaries of evidence and its certainty.

METHODS

We summarised the publicly available Australian GRADE assessments for the use of vaccines for prevention of cholera, diphtheria, tetanus and pertussis, human papillomavirus, influenza, meningococcal, pneumococcal, rabies and varicella zoster virus, including the certainty of evidence for each outcome (e.g., effectiveness, immunological or safety outcomes) and overall, in addition to the reasons for downgrade or upgrade of the certainty assessments.

RESULTS

Across 25 research questions, 189 separate outcomes were assessed; of these 43 (22.8 %), 38 (20.1 %), 68 (36.0 %) and 40 (21.2 %) were classified as informed by very low, low, moderate and high certainty of evidence, respectively. Overall, 4 (16 %), 10 (40 %), 9 (36 %) and 2 (8 %) research questions across the disease areas had their overall certainty of evidence classified as very low, low, moderate and high, respectively. Certainty of evidence was downgraded for confounding, uncertainty in the effect estimation, and differences between the research questions asked by ATAGI and those answered in the studies.

CONCLUSION

There is an unmet need to improve the quality of evidence available to vaccine policy-makers and National Immunisation Technical Advisory Groups. This could be achieved by improving the design of vaccine trials, in particular improving the precision of statistical estimates, inclusion of relevant subpopulations and ensuring trial endpoints are better aligned with the needs of policy-makers.

Broad Mucosal and Systemic Immunity in Mice Induced by Intranasal Booster With a Novel Recombinant Adenoviral Based Vaccine Protects Against Divergent Influenza A Virus

The development of broad-spectrum universal influenza vaccines and optimization of vaccination strategies to address the threats posed by pandemics and emerging influenza viruses are critical for public health. In this study, an adenovirus type 5 vector-based influenza vaccine carrying the hemagglutinin (HA) stem of H1, HA stem of H3, and neuraminidase (NA) of N1 from the influenza virus was constructed. Immune responses were evaluated in mice using various vaccination strategies: prime-only (intramuscular [IM] or intranasal [IN]) and prime-boost (IM + IN). Compared with the prime-only strategy, the prime-boost strategy significantly enhanced the systemic immune response, inducing higher levels of antigen-specific IgG, mucosal IgA, and T cell immunity in the spleen and lungs. Furthermore, the IN boosting strategy provided complete protection in mice challenged with the H1N1-PR8, rgH3N2-X31, and rgH5N1-Vietnam viruses, significantly reducing viral loads in the lungs and alleviating lung tissue pathologies. In conclusion, this study elucidates potential avenues for the development and application of universal influenza vaccines using customized mucosal boosting strategies.

The comprehensive insights into the B-cells-mediated immune response against COVID-19 infection amid the ongoing evolution of SARS-CoV-2

The antibody-mediated immune response is crucial for the development of protective immunity against SARS-CoV-2, the virus responsible for the COVID-19 pandemic. Understanding the interaction between SARS-CoV-2 and the immune system is critical because new variants emerge as a result of the virus's ongoing evolution. Understanding the function of B cells in the SARS-CoV-2 infection process is critical for developing effective and long-lasting vaccines against this virus. Triggered by the innate immune response, B cells transform into memory B cells (MBCs). It is fascinating to observe how MBCs provide enduring immune defence, not only eradicating the infection but also safeguarding against future reinfection. If there is a lack of B cell activation or if the B cells are not functioning properly, it can lead to a serious manifestation of the disease and make immunisation less effective. Individuals with disruptions in the B cells have shown increased production of cytokines and chemokines, resulting in a poor prognosis for the disease. Therefore, we have developed an updated review article to gain insight into the involvement of B cells in SARS-CoV-2 infection. The discussion has covered the generation, functioning, and dynamics of neutralising antibodies (nAbs). Furthermore, we have emphasised immunotherapeutics that rely on nAbs.

T and B cell responses in different immunization scenarios for COVID-19: a narrative review

Vaccines against COVID-19 have high efficacy and low rates of adverse events. However, none of the available vaccines provide sterilizing immunity, and reinfections remain possible. This review aims to summarize the immunological responses elicited by different immunization strategies, examining the roles of homologous and heterologous vaccination and hybrid immunity. Homologous vaccination regimens exhibit considerable variation in immune responses depending on the vaccine platform, particularly concerning antibody titers, B cell activation, and T cell responses. mRNA vaccines, such as mRNA-1273 and BNT162b2, consistently generate higher and more durable levels of neutralizing antibodies and memory B cells compared to adenovirus-based vaccines like Ad26.COV2.S and ChAdOx1. The combination of two distinct vaccine platforms, each targeting different immune pathways, seems to be more effective in promoting long-lasting B cell responses and potent T cell responses. The high heterogeneity of the available studies, the different dosing schemes, the succession of new variants, and the subjects' immunological background do not allow for a definitive conclusion. Overall, heterologous vaccination strategies, combining sequentially viral vector and mRNA may deliver a more balanced and robust humoral and cellular immune response compared to homologous regimens. Hybrid immunity, which arises from SARS-CoV-2 infection preceded or followed by vaccination produces markedly stronger immune responses than either vaccination or infection alone. The immune response to SARS-CoV-2 variants of concern varies depending on both the vaccine platform and prior infection status. Hybrid immunity leads to a broader antibody repertoire, providing enhanced neutralization of variants of concern. Heterologous vaccination and hybrid immunity may provide further opportunities to enhance immune responses, offering broader protection and greater durability of immunity. However, from all-cause mortality, symptomatic or severe COVID, and serious adverse events at present it is not possible to infer different effects between homologous and heterologous schemes. Next-generation vaccines could involve tweaks to these designs or changes to delivery mechanisms that might improve performance.

Incidence of dynamic seroconversion in subjects received the first dose of the SARS-COV-2 vaccine (AstraZeneca, Moderna and Pfizer) in Kinshasa, Democratic Republic of Congo: prospective cohort study

BACKGROUND

Mass vaccination efforts worldwide have reduced the incidence of COVID-19, but despite this reduction, seroconversion studies in sub-Saharan Africa are limited. The aim of this study is to assess the incidence of seroconversion in subjects who received the first dose of SARS-COV-2 vaccine (AstraZeneca, Moderna and Pfizer) in Kinshasa.

METHODS

This was a prospective study recruiting 918 subjects vaccinated at the Cliniques Universitaires de Kinshasa between 19 April and 14 August 2021. Sociodemographic, haematological, biochemical and serological data were collected. Cox proportional hazards were used to identify predictors of seroconversion with a threshold of p < 0.05.

RESULTS

Of the 918 vaccinated individuals, 69.3% were men with a mean age of 47.4 ± 16.0 years. The incidence of seroconversion at last follow-up was 3.00 per 100 P-D. Patients receiving Pfizer (aRR: 3.19; 95% CI: 2.62-3.88) and Modern (aRR: 1.91; 95% CI: 1.60-2.29) vaccines, men (aRR: 2.03; 95% CI: 1.89-3.20), those with comorbidities (aRR: 2.38; 95% CI: 1.89-3.21); subjects with normal creatinine (aRR: 2.08; 95% CI: 1.88-3.32) and normal ALT (aRR: 3.04; 95% CI: 1.89-4.22) were the factors independently predicting seroconversion.

CONCLUSION

The vaccines used had conferred significant immunity on subjects upon receipt of the first dose. This immunity appears to be greater when using the mRNA vaccine than when using the inactivated vaccine.

Hesitancy towards COVID-19 booster vaccine among healthcare workers in Bangladesh

BACKGROUND

Despite completing the COVID-19 vaccination series, healthcare workers (HCWs) remain at an elevated risk of re-infection. Booster uptake, though essential for this group, remains poorly characterized among Bangladeshi HCWs. This study identified the prevalence and driving factors behind booster hesitancy among Bangladeshi HCWs, providing valuable insights for targeted interventions.

METHOD

From December 2022 to June 2023, we conducted a cross-sectional survey among 1772 HCWs enrolled from 20 healthcare facilities of all tiers purposively selected across four administrative divisions of Bangladesh. We collected information through face-to-face interviews regarding their sociodemographic, pre-existing, and currently existing medical conditions, COVID-19 vaccination status, and their intention, hesitancy, and willingness to receive future booster doses. We used a multivariable logistic regression model to analyze factors associated with booster hesitancy. Odd's ratio with 95% confidence intervals (CIs) was calculated for each factor, with p < 0.05 considered statistically significant.

RESULT

Of the 1772 HCWs interviewed in our study, 49% (879) were nurses [median age 36 years (IQR: 30.0-46.0)]; 69% were female. Among the respondents, 94% (1667) were willing to take a booster, and 6% (105) showed hesitancy. Safety concerns, especially regarding potential side effects post-booster administration (86%), emerged as the leading cause of booster hesitancy among healthcare workers. Our multivariable logistic regression analysis revealed that support staff, compared to physicians, were the most hesitant to receive any additional booster dose (aOR 4.68, 95% CI: 1.56-9.03; p=0.006). Compared to rural residency, HCWs with an urban residency type were also more reluctant to receive booster doses (aOR 4.45, 95% CI: 2.03-9.73; p < 0.001).

CONCLUSION

Concerns about side effects following booster administration were the primary driver of hesitancy in our study. Targeted interventions focusing on education and addressing these anxieties-supported by evidence-based communication strategies-could play a crucial role in improving booster acceptance and safeguarding this vulnerable workforce.

The immunogenicity, reactogenicity, and safety of a bivalent mRNA or protein COVID-19 vaccine given as a fourth dose

OBJECTIVES

We conducted a randomised controlled trial (RCT) to compare immunogenicity, reactogenicity and safety one month after a fourth COVID-19 mRNA or protein vaccine dose.

METHODS

This RCT recruited healthy adults in Melbourne, Australia, who had previously received three COVID-19 vaccine doses at least six months prior and had no SARS-CoV-2 infection in the last three months. The participants were randomised (1:1) to receive the bivalent mRNA vaccine (mRNA-1273.214/mRNA-1273.222, hereafter Moderna) or protein vaccine (NVX-CoV-2373, hereafter Novavax) as a fourth dose. A self-selected control group who elected not to receive an additional dose were also included. The co-primary endpoints compared immunogenicity at 28 days post-vaccination measured as binding antibodies (IgG against Ancestral and Omicron subvariants; BA.1, BA.4/5 and JN.1) between the two vaccine groups, and reactogenicity within one-week post-vaccination.

CLINICALTRIALS

gov Identifier: NCT05543356.

RESULTS

Between Feb 28 and Oct 4, 2023, 496 participants were enrolled into the study. Participants were randomised into either the bivalent mRNA Moderna (n=177) or protein Novavax (n=176) vaccine groups, with n=143 allocated to the control group. The geometric mean ratio (GMR) of anti-Spike binding IgG antibody levels were higher for the Moderna vaccine compared to the Novavax vaccine at 28 days post-vaccination for all variants tested, including Ancestral (GMR: 2.11, 95% CI: 1.88 - 2.37), BA.1 (GMR: 2.32, 95% CI 2.04 - 2.63), BA.4/5 (GMR: 2.32, 95% CI: 2.04 - 2.65), and JN.1 (GMR: 2.40, 95% CI: 2.14 - 2.70). The frequency of any local and systemic reactions (grades 1-4) was higher for the Moderna vaccine (159/177; 89.8%) compared to the Novavax vaccine (130/176; 73.9%). Serious reactions (grade 3-4) between the groups were similar (11/177; 6.2%, versus 9/176; 5.1%, respectively).

CONCLUSION

At day 28 post-vaccination, higher immunogenicity was observed following Moderna vaccination compared to Novavax vaccination when given as a fourth dose in healthy adults for Ancestral and Omicron subvariants, including JN.1. However, local and systemic reactogenicity was higher in the Moderna vaccine group compared with the Novavax vaccine group. These results may have important implications for ongoing booster strategies.

Epitope-focused vaccine immunogens design using tailored horseshoe-shaped scaffold

The continuous emergence of severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) variants highlights the need to update coronavirus 2019 disease (COVID-19) vaccine components. Epitope-based vaccine designs targeting conserved and immunorecessive regions of SARS-CoV-2 are critically needed. Here, we report an engineered epitope-focused immunogen design based on a novel horseshoe-shaped natural protein scaffold, named ribonuclease inhibitor 1 (RNH1), that can multiply display of conserved neutralizing epitopes from SARS-CoV-2 S2 stem helix. The designed immunogen RNH1-S1139 demonstrates high binding affinity to S2-specific neutralizing antibodies and elicits robust epitope-targeted antibody responses either through homologous or heterologous vaccination regimens. RNH1-S1139 immune serum has been proven to have similar binding ability against SARS-CoV, SARS-CoV-2 and its variants, providing broad-spectrum protection as a membrane fusion inhibitor. Further studies showed that RNH1 has the potential to serve as a versatile scaffold that displays other helical epitopes from various antigens, including respiratory syncytial virus (RSV) F glycoprotein. Our proposed immunogen engineering strategy via tailored horseshoe-shape nano-scaffold supports the continued development of epitope-focused vaccines as part of a next-generation vaccine design.

Cost-Effectiveness of Introducing Nuvaxovid to COVID-19 Vaccination in the United Kingdom: A Dynamic Transmission Model

Background/Objectives: Vaccination against SARS-CoV-2 remains a key measure to control COVID-19. Nuvaxovid, a recombinant Matrix-M-adjuvanted protein-based vaccine, showed similar efficacy to mRNA vaccines in clinical trials and real-world studies, with lower rates of reactogenicity. Methods: To support decision making on UK vaccine selection, a population-based compartmental dynamic transmission model with a cost-utility component was developed to evaluate the cost-effectiveness of Nuvaxovid compared with mRNA vaccines from a UK National Health Service perspective. The model was calibrated to official epidemiology statistics for mortality, incidence, and hospitalisation. Scenario and sensitivity analyses were conducted. Results: In the probabilistic base case, a Nuvaxovid-only strategy provided total incremental cost savings of GBP 1,338,323 and 1558 additional quality-adjusted life years (QALYs) compared with an mRNA-only vaccination strategy. Cost savings were driven by reduced cold chain-related operational costs and vaccine wastage, while QALY gains were driven by potential differences in vaccine tolerability. Probabilistic sensitivity analysis indicated an approximately 70% probability of cost-effectiveness with Nuvaxovid-only versus mRNA-only vaccination across most cost-effectiveness thresholds (up to GBP 300,000/QALY gained). Conclusions: Nuvaxovid remained dominant over mRNA vaccines in scenario analyses assessing vaccine efficacy waning, Nuvaxovid market shares, and the vaccinated population.

Self-reported longitudinal COVID-19 vaccination reactogenicity profiles in persons with multiple sclerosis

BACKGROUND

Preventing severe COVID-19 associated outcomes continues to be a priority for persons with multiple sclerosis (PwMS). We previously reported in an interim analysis that short-term reactions to the first and second SARS-CoV-2 vaccines experienced by PwMS were mostly self-limiting and similar to reactions experienced by the general population.

OBJECTIVES

First, to report short-term reactogenicity experienced by PwMS in relation to the first through fourth SARS-CoV-2 vaccines. Second, to report on short-term reactogenicity in PwMS for different sequences of the first three vaccines.

METHODS

Between March 2021 to March 2023, PwMS electronically self-reported SARS-CoV-2 vaccines, local and systemic reactions within 24 hours for each vaccine, and other clinical and demographic information. Multivariable models examined associations with reactogenicity after the first, second, third, and fourth vaccine. Similar models examined associations with reactogenicity after the third vaccine for specific vaccine sequences.

RESULTS

There were 1,087 PwMS, 722 PwMS, 263 PwMS, and 110 PwMS who provided information on the first and second vaccine and subsequent vaccines/boosters, respectively. 60 % reported a reaction after the first vaccine, compared to 71 % after the second, 62 % after the third, and 54 % after the fourth. 17 % reported a severe reaction after the first vaccine, while 22 % after the second, 16 % after the third, and 14 % after the fourth. Across most models, age and being on an sphingosine-1-phosphate receptor modulator were inversely associated with experiencing a reaction. Those who received mRNA-1273 (M) vs BNT162b2 (B) vaccine as the first through third vaccine, appeared to experience a high burden of reactions. Disease course, disease severity, and other demographic attributes were not associated with reactions after the third and fourth vaccines. PwMS who had the M-M-M sequence were more likely to report any and severe local reactions, the B-B-M sequence were more likely to report any severe and any severe systemic reactions, while the M-M-B sequence were less likely to report any reaction, in comparison to PwMS who only had the B-B-B sequence.

DISCUSSION

Our findings demonstrate that, in general, the short-term vaccine reactions experienced by PwMS are self-limiting, and their frequencies decrease with each subsequent vaccine/booster after peaking in response to the second vaccine. Those receiving mRNA-1273 as the third vaccine reported more reactions than those receiving BNT162b2.

Modelling antibody dynamics in humans after different Ad26.COV2.S vaccination schemes

AIMS

To develop a semimechanistic model that describes the kinetic profile and variability of antibody (Ab) concentrations following vaccination with Ad26.COV2.S at different doses and dosing intervals.

METHODS

Data were collected from participants randomized into 5 clinical trials receiving the Ad26.COV2.S vaccine. The model considered key elements of humoral immune response, dose proportionality and the evolutionary processes of the immune response. Interindividual variability and covariates were explored.

RESULTS

Fast and slow kinetic phases of Ab and their evolution over time were differentiated. After first and second administrations, Ab concentrations of both phases increased less than dose proportionally, indicating a saturation of B-cell production processes. Ab concentrations produced during the fast kinetic phase increased significantly after the second administration, indicating an underlying evolutive process after antigen exposures. For the slow kinetic phase, a less pronounced increase occurred after the second and third administrations but was relatively higher in subjects who had low concentrations after the first administration. Ab concentrations of the slow phase were higher in females and decreased with age. After multiple administrations, the fast phase had Ab maximum concentrations about 5 times higher than the slow phase. The limiting kinetic factors in the fast and slow phases were the elimination rates of Ab itself and Ab producing cells, respectively.

CONCLUSION

The model appears suitable to quantitatively describe the inter- and intraindividual kinetics of the immune response and the impact of covariates after multiple administrations of a vaccine.

Past, present, and future of Phase 3 vaccine trial design: rethinking statistics for the 21st century

Vaccines are crucial for protecting health globally; however, their widespread use relies on rigorous clinical development programmes. This includes Phase 3 randomized controlled trials (RCTs) to confirm their safety, immunogenicity, and efficacy. Traditionally, such trials used fixed designs with predetermined assumptions, lacking the flexibility to change during the trial or stop early due to overwhelming evidence of either efficacy or futility. Modern vaccine trials benefit from innovative approaches like adaptive designs, allowing for planned trial adaptations based on accumulating data. Here, we provide an overview of the evolution of Phase 3 vaccine trial design and statistical analysis methods from traditional to more innovative contemporary methods. This includes adaptive trial designs, which offer ethical advantages and enable early termination if indicated; Bayesian methods, which combine prior knowledge and observed trial data to increase efficiency and enhance result interpretation; modern statistical analysis methods, which enable more accurate and precise inferences; the estimand framework, which ensures the primary question of interest is addressed in a trial; novel approaches using machine learning methods to assess heterogeneity of treatment effects; and statistical advances in safety analysis to evaluate reactogenicity and clinical adverse events. We conclude with insights into the future direction of vaccine trials, aiming to inform clinicians and researchers about conventional and novel RCT design and analysis approaches to facilitate the conduct of efficient, timely trials.

Local and systemic reactogenicity after mRNA and protein-based COVID-19 vaccines compared to meningococcal vaccine (MenACWY) in a UK blinded, randomized phase 2 trial (COV-BOOST)

Reactogenicity, the occurrence of vaccine side effects, can impact vaccine acceptance. There is limited data comparing the reactogenicity of COVID-19 vaccines to other routinely used vaccines, such as the meningococcal conjugate vaccine (MenACWY). In a trial of UK adults, participants received a third COVID-19 vaccine dose (NVX-CoV2373, BNT162b2, or mRNA1273) alongside MenACWY as an active control. Compared to MenACWY, we found that mRNA vaccines, particularly mRNA1273, showed the greatest relative increase in side effects, while protein-based NVX-CoV2373 generally elicited similar reactogenicity to MenACWY. These findings suggest that platform type can influence vaccine reactogenicity, and further research is needed to compare COVID-19 vaccines with other routinely administered vaccines.

Linking COVID-19 and cancer: Underlying mechanism

COVID-19 caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), lead to a global health crisis with a spectrum of clinical manifestations. A potentially vulnerable category for SARS-CoV-2 infection was identified in patients with other medical conditions. Intriguingly, parallels exist between COVID-19 and cancer at the pathophysiological level, suggesting a possible connection between them. This review discusses all possible associations between COVID-19 and cancer. Expression of receptors like angiotensin-converting enzyme 2 (ACE2) and transmembrane protease serine 2 (TMPRSS2) increases COVID-19 susceptibility. SARS-CoV-2 infection might increase cancer susceptibility and accelerate cancer progression through mechanisms involving cytokine storm, tissue hypoxia, impaired T-cell responses, autophagy, neutrophil activation, and oxidative stress. These mechanisms collectively contribute to immune suppression, hindered apoptosis, and altered cellular signaling in the tumor microenvironment, creating conditions favorable for tumor growth, metastasis, and recurrence. Approved vaccines and their impact on cancer patients along-with new clinical trials are also described.

Safety and immunogenicity of a modified mRNA-lipid nanoparticle vaccine candidate against COVID-19: Results from a phase 1, dose-escalation study

This phase 1, open-label, dose-escalation, multi-center study (NCT05477186) assessed the safety and immunogenicity of a booster dose of an mRNA COVID-19 vaccine (CV0501) encoding the SARS-CoV-2 Omicron BA.1 spike protein. Participants aged ≥ 18 years previously vaccinated with ≥ 2 doses of an mRNA COVID-19 vaccine received CV0501 doses ranging from 12 to 200 μg. After assessment of safety and immunogenicity of the 12 μg dose in 30 adults, 30 adults ≤ 64 years were randomized to receive either a 3 or 6 μg dose. Solicited adverse events (AEs) were collected for 7 days, unsolicited AEs for 28 days, and serious AEs (SAEs), medically attended AEs (MAAEs), and AEs of special interest (AESIs) until day (D) 181 post-vaccination. Serum neutralizing titers specific to SARS-CoV-2 BA.1, wild-type, Delta, and additional Omicron subvariants were assessed at D1, D15, D29, D91, and D181. Of 180 vaccinated participants (mean age: 49.3 years; 57.8% women), 70.6% had prior SARS-CoV-2 infection. Most solicited local (98.1%) and systemic (96.7%) AEs were of mild-to-moderate severity; the most common were injection site pain (57.5%; 33.3-73.3% across groups) and myalgia (36.9%; 13.3-56.7%). Unsolicited AEs were reported by 14.4% (6.7-26.7%) of participants (mild-to-moderate severity in 88.5% of the participants). Three participants (1.7%) reported SAEs, 16.7% (6.7-30.0%) reported MAAEs, and 8.3% (0.0-13.3%) reported AESIs (15 COVID-19 cases), none related to vaccination. Geometric means of serum neutralizing titers increased from baseline to D15 and D29 (dose-dependent), and then decreased over time. The safety and immunogenicity results supported advancement to a phase 2 trial.

Seropersistence of SII-ChAdOx1 nCoV-19 (COVID-19 vaccine): 6-month follow-up of a randomized, controlled, observer-blind, phase 2/3 immuno-bridging study in Indian adults

AZD1222 (ChAdOx1 nCoV-19) is a replication-deficient adenoviral vectored coronavirus disease-19 (COVID-19) vaccine that is manufactured as SII-ChAdOx1 nCoV-19 by the Serum Institute of India Pvt Ltd following technology transfer from Oxford University/AstraZeneca. The non-inferiority of SII-ChAdOx1 nCoV-19 with AZD1222 was previously demonstrated in an observer-blind, phase 2/3 immuno-bridging study (trial registration: CTRI/2020/08/027170). In this analysis of immunogenicity and safety data 6 months post first vaccination (Day 180), 1,601 participants were randomized 3:1 to SII-ChAdOx1 nCoV-19 or AZD1222 (immunogenicity/reactogenicity cohort n = 401) and 3:1 to SII-ChAdOx1 nCoV-19 or placebo (safety cohort n = 1,200). Immunogenicity was measured by anti-severe acute respiratory syndrome coronavirus 2 spike (anti-S) binding immunoglobulin G and neutralizing antibody (nAb) titers. A decline in anti-S titers was observed in both vaccine groups, albeit with a greater decline in SII-ChAdOx1 nCoV-19 vaccinees (geometric mean titer [GMT] ratio [95% confidence interval (CI) of SII-ChAdOx1 nCoV-19 to AZD1222]: 0.60 [0.41-0.87]). Consistent similar decreases in nAb titers were observed between vaccine groups (GMT ratio [95% CI]: 0.88 [0.44-1.73]). No cases of severe COVID-19 were reported following vaccination, while one case was observed in the placebo group. No causally related serious adverse events were reported through 180 days. No thromboembolic or autoimmune adverse events of special interest were reported. Collectively, these data illustrate that SII-ChAdOx1 nCoV-19 maintained a high level of immunogenicity 6 months post-vaccination. SII-ChAdOx1 nCoV-19 was safe and well tolerated.

Comparing the protection of heterologous booster of inhaled Ad5-nCoV vaccine and hybrid immunity against Omicron BA.5 infection: a cohort study of hospital staff in China

BACKGROUND

After the exit "zero-COVID" strategy in mainland China by the end of 2022, a large-scale COVID-19 outbreak seeded by Omicron variants occurred. An inhaled adenovirus type-5 vector-based (i.e., inhaled Ad5-nCoV) COVID-19 vaccine was licensed earlier in 2021. In this study, we aimed to assess the real-world effectiveness of a heterologous booster of inhaled Ad5-nCoV vaccine against Omicron infection and compared with the protection from hybrid immunity (i.e., prior breakthrough infection).

METHODS

In this retrospective cohort study, we identified 1087 out of a total of 1146 hospital staff from a tertiary hospital in Urumqi city, China from November 22 to December 29, 2022. Demographic characteristics, baseline health status, occupation, behavioral factors, laboratory test of serological IgG antibody, and timeline from immunization to laboratory-testing outcome were obtained. We analysed the individual-level vaccination status of inhaled Ad5-nCoV vaccine, prior SARS-CoV-2 infection status and baseline vaccination status, and other risk factors before follow-up. The protective effects of the heterologous inhaled Ad5-nCoV vaccine and hybrid immunity against Omicron BA.5 infection and hospitalization were calculated as relative rate reduction (RRR), which was estimated using multivariate Poisson regression models.

RESULTS

A total of 1087 hospital staff (median age of 34 years, and 343 males [31.6%]), including 931 accepted for serological antibody tests, were recruited to assess the vaccine effectiveness (VE) of the inhaled Ad5-nCoV booster and hybrid immunity. Among the 1087 participants, 413 had a history of prior SARS-CoV-2 infection (before follow-up) but did not receive an inhaled Ad5-nCoV booster, and 674 reported no prior infection, including 390 who received an inhaled Ad5-nCoV booster. The highest serological IgG antibody level was detected among the inhaled Ad5-nCoV group, with a median of 294.59 S/CO, followed by the hybrid immunity group, with a median of 93.65 S/CO compared to the reference level of the inactivated vaccine group (most of whom received the Sinopharm/BBIBP-CorV vaccine). The inhaled Ad5-nCoV booster and hybrid immunity yielded RRRs of 41.9% (95% CI: 24.8, 55.0) and 97.9% (95% CI: 94.2, 99.2), respectively, against Omicron BA.5 infection, regardless of symptom status.

CONCLUSION

We found that hybrid immunity could provide a high level of protection against Omicron infection, while a heterologous inhaled Ad5-nCoV booster conferred a moderate level of protection. Our findings supported the rollout of a heterologous vaccination strategy regardless of preexisting vaccine coverage.

Booster COVID-19 mRNA vaccination ameliorates impaired B-cell but not T-cell responses in older adults

Age-associated differences in the effect of repetitive vaccination, particularly on memory T-cell and B-cell responses, remain unclear. While older adults (aged ≥65 years) exhibited enhanced IgG responses following COVID-19 mRNA booster vaccination, they produced fewer spike-specific circulating follicular helper T cells-1 than younger adults. Similarly, the cytotoxic CD8+ T-cell response remained diminished with reduced PD-1 expression even after booster vaccination compared with that in younger adults, suggesting impaired memory T-cell activation in older adults. In contrast, although B-cell responses in older adults were weaker than those in younger adults in the primary response, the responses were significantly enhanced upon booster vaccination, reaching levels comparable with that observed in younger adults. Therefore, while booster vaccination ameliorates impaired humoral immunity in older adults by efficiently stimulating memory B-cell responses, it may less effectively enhance T-cell-mediated cellular immunity. Our study provides insights for the development of effective therapeutic and vaccine strategies for the most vulnerable older population.

The Platform Trial In COVID-19 priming and BOOsting (PICOBOO): The immunogenicity, reactogenicity, and safety of licensed COVID-19 vaccinations administered as a second booster in BNT162b2 primed individuals aged 18-<50 and 50-<70 years old

OBJECTIVES

PICOBOO is a randomised, adaptive trial evaluating the immunogenicity, reactogenicity, and safety of COVID-19 booster strategies. Here, we present data for second boosters among individuals aged 18-<50 and 50-<70 years old primed with BNT162b2 until Day (D) 84.

METHODS

Immunocompetent adults who had received two doses of BNT162b2 and any licensed COVID-19 booster at least three months prior were eligible. Participants were randomly allocated to BNT162b2, mRNA-1273 or NVX-CoV2373 1:1:1. The log10 concentration of anti-spike Ig Total was summarised as the geometric mean concentration (GMC). Reactogenicity and safety outcomes were captured.

RESULTS

Between Mar 2022 and Aug 2023, 743 participants were recruited to the trial and had D28 samples available. Of these, 120 and 103 belonged to the 18-<50 y and 50-<70 y strata, respectively. The mean adjusted GMCs (95% credible intervals) peaked at D28; these were 41 262 (31 611, 51 105), 45 585 (34 194, 57 441) and 25 281 (20 021, 31 234) U/mL in the 18-<50 y stratum and 30 753 (25 071, 36 704), 35 132 (27 523, 42 239) and 17 322 (13 983, 20 641) U/mL in the 50-<70 y stratum following BNT162b2, mRNA-1273 and NVX-CoV2373, respectively. Limited neutralisation against Omicron subvariants was found following boosting with all vaccines. There were 4 possibly or probably-related adverse events in the 18-<50 y stratum and 5 events in the 50-<70 y stratum, and severe reactogenicity events were <10% and <11% in these strata, respectively.

CONCLUSIONS

Vaccines targeting Ancestral virus elicited boosted antibody responses to Ancestral virus but minimal neutralising antibody against Omicron variants.

Comparative study of anti-SARS-CoV-2 receptor-binding domain total antibody titer before and after heterologous booster with mRNA-based COVID-19 vaccine

The waning immunity following the COVID-19 vaccination become a significant concern and the immunological dynamics of vaccine-induced antibodies after vaccination need to be explored. The aim of this study was to compare anti-SARS-CoV-2 receptor-binding domain (RBD) antibody levels before and after a booster dose with heterologous COVID-19 vaccine and to identify factors influencing the levels after receiving the booster dose. A cross-sectional study was conducted in which individuals who received primary doses of CoronaVac and a booster dose with an mRNA-based vaccine were recruited using a purposive sampling technique. The titers of anti-SARS-CoV-2 RBD antibodies were measured using an enzyme-linked immunosorbent assay (ELISA), and plausible associated factors were collected using a questionnaire-assisted face-to-face interview. The Wilcoxon test was used to compare the titers before and after the booster dose, while the Kruskal-Wallis and Mann-Whitney tests, followed by multivariate linear regression, were used to assess the factors associated with RBD total antibody titers. The results showed that there was a significant increase of anti-SARS-CoV-2 RBD total antibody titers before and after receiving the booster dose (1,558.7 binding antibody units (BAU)/mL vs 140.6 BAU/mL, p<0.001). The analysis revealed that age (p=0.555), sex (p=0.254), type of vaccine (p=0.914), presence of hypertension (p=0.541), diabetes (p=0.975), chronic obstructive pulmonary disease (COPD, p=0.620), and gout (p=0.364) were not associated with anti-SARS-CoV-2 RBD total antibody titers. However, the titers of anti-SARS-CoV-2 RBD total antibody were significantly different between those with and without hyperlipidemia (p=0.021). This study suggests that a booster dose with a heterologous COVID-19 vaccine could significantly enhance immune responses against COVID-19, and therefore, this strategy may be recommended as part of preventive measures to strengthen immunity against COVID-19.

Mechanisms and implications of IgG4 responses to SARS-CoV-2 and other repeatedly administered vaccines

Vaccine-induced immunoglobulin G (IgG) profiles can vary with respect to the predominant subclasses that characterize the response. Among IgG subclasses, IgG4 is reported to have anti-inflammatory properties, but can also exhibit reduced capacity for virus neutralization and activation of Fc-dependent effector functions. Here, we review evidence that IgG4 subclass responses can be disproportionately increased in response to some types of vaccines targeting an array of diseases, including pertussis, HIV, malaria, and COVID-19. The basis for enhanced IgG4 induction by vaccines is poorly understood but may be associated with platform- or dose regimen-specific differences in antigen exposure and/or cytokine stimulation. The clinical implications of vaccine-induced IgG4 responses remain uncertain, though collective evidence suggests that proportional increases in IgG4 might reduce vaccine antigen-specific immunity. Additional work is needed to determine underlying mechanisms and to elucidate what role IgG4 may play in modifications of vaccine-induced immunity to disease.

Longitudinal Immunological Analysis of Portuguese Healthcare Workers Across the COVID-19 Pandemic Reveals Differences in the Humoral Immune Response to Vaccines

Background: A vaccination programme against severe acute respiratory syndrome coronavirus 2 was initiated in Portugal in December 2020. In this study, we report the findings of a prospective cohort study implemented with the objective of monitoring antibody production in response to COVID-19 vaccination. Methods: The humoral immune response to vaccination was followed up using blood samples collected from 191 healthcare workers. Participants were split into three groups: the Oxford-AstraZeneca (Vaxzevria) vaccine group (n = 68), the Pfizer-BioNTech COVID-19 (Comirnaty) vaccine group (n = 51), and the Post-COVID group (n = 72). The kinetics of anti-spike antibody production were evaluated until 56 days on average after the third dose (booster). Results: We observed that antibody titres peaked approximately one month after full vaccination and declined steadily thereafter. We also found that mRNA vaccination induces higher titres of antibodies than viral vector vaccination, and both generate greater antibody responses than mild or moderate COVID-19. Additionally, whilst the booster for the Oxford-AstraZeneca and Pfizer-BioNTech groups led to antibody levels higher than those at any previous sample collection point, the booster for the Post-COVID group (persons with a history of COVID-19 prior to vaccination) led to antibody levels lower than those attained one month after the second dose. Interpretation: Our results indicate that there are different kinetics of antibody production between individuals who received the Pfizer-BioNtech mRNA vaccine and those who received the Oxford-AstraZeneca vector vaccine, or individuals who had COVID-19 before being vaccinated. Additionally, we observed that exposure to either natural infection or vaccination modulates the response to subsequent vaccination. This is particularly evident after administration of the third dose to the Post-COVID group, where our findings point to a hindrance in vaccine boosting, probably due to unwanted feedback by high titres of pre-existing antibodies.

Case-cohort design as an efficient approach to evaluating COVID-19 vaccine effectiveness, waning, heterologous immune effect and optimal dosing interval

Though widely applied in other epidemiological fields, the case-cohort study design has seen little application in the field of vaccinology. Case-cohort studies use probabilistic sampling and reweighting to draw inferences about effects (in this case vaccine efficacy) at the population level in an efficient manner. The SARS-CoV-2 pandemic was met with high vaccine uptake, and high rates of population testing prior to the emergence of Omicron variants of concern, in Ontario, Canada, providing an ideal environment for application of case-cohort methodology. We combined a population-based case line list and vaccination database for the province of Ontario between December 2020 and October 2021. Risk of infection after vaccination was evaluated in all laboratory-confirmed vaccinated SARS-CoV-2 cases, and a 2 % sample of vaccinated controls, evaluated using survival analytic methods, including construction of Cox proportional hazards models. Vaccination status was treated as a time-varying covariate. First and second doses of SARS-CoV-2 vaccine markedly reduced risk of infection (first dose efficacy 68 %, 95 % CI 67 %-69 %; second dose efficacy 88 %, 95 % CI 87-88 %). In multivariable models, extended dosing intervals were associated with lowest risk of breakthrough infection (HR for redosing 0.64 (95 % CI 0.61-0.67) at 6-8 weeks). Heterologous vaccine schedules that mixed viral vector vaccine first doses with mRNA second doses were significantly more effective than mRNA only vaccines. Risk of infection largely vanished during the time period 4-6 months after the second vaccine dose, but rose markedly thereafter. We conclude that a case-cohort design provided an efficient means to identify strong protective effects associated with SARS-CoV-2 vaccination in real time, and also served to quantify the timing and magnitude of infection breakthrough risk in the same cohort. Heterologous vaccination and extended dosing intervals improved the durability of immune response.

The Ambivalence of Post COVID-19 Vaccination Responses in Humans

The Coronavirus disease 2019 (COVID-19) pandemic, caused by severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), has prompted a massive global vaccination campaign, leading to the rapid development and deployment of several vaccines. Various COVID-19 vaccines are under different phases of clinical trials and include the whole virus or its parts like DNA, mRNA, or protein subunits administered directly or through vectors. Beginning in 2020, a few mRNA (Pfizer-BioNTech BNT162b2 and Moderna mRNA-1273) and adenovirus-based (AstraZeneca ChAdOx1-S and the Janssen Ad26.COV2.S) vaccines were recommended by WHO for emergency use before the completion of the phase 3 and 4 trials. These vaccines were mostly administered in two or three doses at a defined frequency between the two doses. While these vaccines, mainly based on viral nucleic acids or protein conferred protection against the progression of SARS-CoV-2 infection into severe COVID-19, and prevented death due to the disease, their use has also been accompanied by a plethora of side effects. Common side effects include localized reactions such as pain at the injection site, as well as systemic reactions like fever, fatigue, and headache. These symptoms are generally mild to moderate and resolve within a few days. However, rare but more serious side effects have been reported, including allergic reactions such as anaphylaxis and, in some cases, myocarditis or pericarditis, particularly in younger males. Ongoing surveillance and research efforts continue to refine the understanding of these adverse effects, providing critical insights into the risk-benefit profile of COVID-19 vaccines. Nonetheless, the overall safety profile supports the continued use of these vaccines in combating the pandemic, with regulatory agencies and health organizations emphasizing the importance of vaccination in preventing COVID-19's severe outcomes. In this review, we describe different types of COVID-19 vaccines and summarize various adverse effects due to autoimmune and inflammatory response(s) manifesting predominantly as cardiac, hematological, neurological, and psychological dysfunctions. The incidence, clinical presentation, risk factors, diagnosis, and management of different adverse effects and possible mechanisms contributing to these effects are discussed. The review highlights the potential ambivalence of human response post-COVID-19 vaccination and necessitates the need to mitigate the adverse side effects.

Diverse BCR usage and T cell activation induced by different COVID-19 sequential vaccinations

Limited knowledge is available on the differences in severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) specific antibody breadth and T cell differentiation among different COVID-19 sequential vaccination strategies. In this study, we compared the immunogenicity of the third different dose of COVID-19 vaccines, such as mRNA (I-I-M), adenoviral vector (I-I-A), and recombinant protein (I-I-R) vaccines, in terms of the magnitude and breadth of antibody response and differentiation of SARS-CoV-2-specific T and B cells. These studies were performed in the same clinical trial, and the samples were assessed in the same laboratory. IGHV1-69, IGHV3-9, and IGHV4-34 were the dominant B cell receptor (BCR) usages of the I-I-M, I-I-A, and I-I-R groups, respectively; the RBD+ B cell activation capacities were comparable. Additionally, the I-I-R group was characterized by higher numbers of regulatory T cells, circulating T follicular helper cells (cTFH) - cTFH1 (CXRC3+CCR6-), cTFH1-17 (CXRC3+CCR6+), cTFH17 (CXRC3-CCR6+), and cTFH-CM (CD45RA-CCR7+), and lower SMNE+ T cell proliferative capacity than the other two groups, whereas I-I-A showed a higher proportion and number of virus-specific CD4+ T cells than I-I-R, as determined in ex vivo experiments. Our data confirmed different SARS-CoV-2-specific antibody profiles among the three different vaccination strategies and also provided insights regarding BCR usage and T/B cell activation and differentiation, which will guide a better selection of vaccination strategies in the future.

IMPORTANCE

Using the same laboratory test to avoid unnecessary interference due to cohort ethnicity, and experimental and statistical errors, we have compared the T/B cell immune response in the same cohort sequential vaccinated by different types of COVID-19 vaccine. We found that different sequential vaccinations can induce different dominant BCR usage with no significant neutralizing titers and RBD+ B-cell phenotype. Recombinant protein vaccine can induce higher numbers of regulatory T cells, circulating TFH (CTFH)1, CTFH17, and CTFH-CM, and lower SMNE+ T-cell proliferative capacity than the other two groups, whereas I-I-A showed higher proportion and number of virus-specific CD4+ T cells than I-I-R. Overall, our study provides a deep insight about the source of differences in immune protection of different types of COVID-19 vaccines, which further improves our understanding of the mechanisms underlying the immune response to SARS-CoV-2.

Comparable antibody levels in heterologous and homologous mRNA COVID-19 vaccination, with superior neutralizing and IgA antibody responses in mRNA homologous boosting

BACKGROUND

Priming with two doses of AZD1222 (Oxford-AstraZeneca; ChAd) followed by a third mRNA vaccine boosting is considered in several countries, yet comparisons between heterologous and homologous booster efficacy remain unexplored.

AIM

To evaluate and contrast the immunogenicity of homologous and heterologous boosting regimens.

METHOD

The study examined antibody responses in 1113 subjects, comprising 895 vaccine-naïve individuals across different vaccination strategies (partial, primary series, heterologous booster, homologous booster) and 218 unvaccinated, naturally infected individuals. Assessments included neutralizing total antibodies (NTAbs), total antibodies (TAbs), anti-S-RBD IgG, and anti-S1 IgA levels.

RESULTS

The study found mRNA vaccines to exhibit superior immunogenicity in primary series vaccination compared to ChAd, with mRNA-1273 significantly enhancing NTAbs, TAbs, anti-S-RBD IgG, and anti-S1 IgA levels (p < 0.001). Both booster types improved antibody levels beyond primary outcomes, with no significant difference in TAbs and anti-S-RBD IgG levels between regimens. However, homologous mRNA boosters significantly outperformed heterologous boosters in enhancing NTAbs and anti-S1 IgA levels, with the BNT/BNT/BNT regimen yielding particularly higher enhancements (p < 0.05).

CONCLUSION

The study concludes that although TAbs and anti-S-RBD IgG antibody levels are similar for both regimens, homologous mRNA boosting outperform heterologous regimen by enhancing anti-S1 IgA and neutralizing antibody levels.

Enhanced RBD-Specific Antibody Responses and SARS-CoV-2-Relevant T-Cell Activity in Healthcare Workers Following Booster Vaccination

COVID-19 continues to impact healthcare workers (HCWs), making it crucial to investigate vaccine response rates. This study examined HCWs' humoral and cellular immunological responses to COVID-19 booster dosages. We enrolled thirty-four vaccinated HCWs. Twelve received a booster. Post-immunization, the participants' anti-COVID-19 IgG antibodies and IFN-γ secretion were assessed. The median second immunization response time was 406.5 days. Eighteen of twenty-two (81.8%) experienced breakthrough infections after the second vaccination, whereas ten out of twelve individuals who received booster doses had breakthrough infections (83.3%). Six of thirty-four HCWs (17.6%) had no breakthrough infections. Booster-injection recipients had a median antibody titer of 19,592 AU/mL, compared to 7513.55 AU/mL. HCWs with breakthrough infections exhibited a median antibody titer of 13,271.9 AU/mL, compared to 7770.65 AU/mL for those without infections. Breakthrough-infection and booster-injection groups had a slightly higher median T-cell response to antigens 1, 2, and 3. SARS-CoV-2 antibody titer and T-cell responsiveness were positively associated. HCWs sustain cellular and humoral immunity for over 10 months. Irrespective of the type of vaccine, booster injections enhance these immune responses. The results of our research are consistent with previous studies, and a multicenter investigation could validate the findings.

Persistent longitudinal T cell responses after SARS-CoV-2 mRNA vaccines in MS patients on different disease modifying treatments

Few data are available regarding vaccine induced SARS-CoV-2 specific T cell responses over time and after booster doses in multiple sclerosis (MS) patients on different disease modifying treatments. We measured SARS-CoV-2 specific CD4+ T cell responses in 72 samples collected from 36 MS patients. The percentage of CD4+ CTVlow CD25+ ICOS+ T cells after stimulation with Spike Recombinant Protein was 29.9 (17.0-43.6) on teriflunomide, 32.4 (11.9-42.5) on ocrelizumab, but much lower (0.6 [0.3-5.9]) on sphingosine-1-phospate receptor modulators (β = -26.35, p = 0.003). SARS-CoV-2 specific T cells were mainly of Th1 type and stable over time and after booster vaccine doses. mRNA vaccines elicit strong and persistent CD4+ T cell responses against SARS-CoV-2 in MS patients on anti-CD20 and teriflunomide, but not in those on sphingosine-1-phospate receptor modulators.

The Potential of mRNA Vaccines to Fight Against Viruses

Vaccines have always been a critical tool in preventing infectious diseases. However, the development of traditional vaccines often takes a long time and may struggle to address the challenge of rapidly mutating viruses. The emergence of mRNA technology has brought revolutionary changes to vaccine development, particularly in rapidly responding to the threat of emerging viruses. The global promotion of mRNA vaccines against severe acute respiratory syndrome coronavirus 2 has demonstrated the importance of mRNA technology. Also, mRNA vaccines targeting viruses such as influenza, respiratory syncytial virus, and Ebola are under development. These vaccines have shown promising preventive effects and safety profiles in clinical trials, although the duration of immune protection is still under evaluation. However, the development of mRNA vaccines also faces many challenges, such as stability, efficacy, and individual differences in immune response. Researchers adopt various strategies to address these challenges. Anyway, mRNA vaccines have shown enormous potential in combating viral diseases. With further development and technological maturity, mRNA vaccines are expected to have a profound impact on public health and vaccine equity. This review discussed the potential of mRNA vaccines to fight against viruses, current progress in clinical trials, challenges faced, and future prospects, providing a comprehensive scientific basis and reference for future research.

Safety and antibody responses of Omicron BA.4/5 bivalent booster vaccine among hybrid immunity with diverse vaccination histories: A cohort study

This cohort study, conducted between July and August 2023, evaluated the adverse events (AEs) and immune response to a bivalent mRNA-1273.222 (containing sequences of the original Wuhan-H1 strain and the Omicron BA.4/5 variant) booster vaccine in 122 participants. The study included individuals with diverse vaccination histories, and their responses were assessed based on anti-receptor binding domain (RBD) IgG levels and neutralizing antibodies against the wild-type, Omicron BA.5, and XBB.1.16 variants. Following administration of the BA.4/5 bivalent vaccine, AEs were generally mild to moderate and well-tolerated within a few days. There were no reports of vomiting and no serious AEs or death. The findings demonstrated robust immune responses, with significant increases in anti-RBD IgG levels, particularly in groups that had received 3 -6 doses before the booster dose. The BA.4/5 bivalent booster effectively induced neutralizing antibodies against the vaccine strains, providing robust neutralization, including the XBB.1.16 strain. The study also highlighted that individuals with hybrid immunity, especially those assumed infected with the BA.5 strain or who had been infected twice, showed higher levels of robust neutralizing activity against Omicron XBB.1.16. Overall, these results indicate that the BA.4/5 bivalent booster vaccines can induce potent and good antibody responses in emerging Omicron subvariants, supporting its efficacy as a booster in individuals with diverse vaccination histories.

[The Molecular and Biological Patterns Underlying Sustained SARS-CoV-2 Circulation in the Human Population]

INTRODUCTION

For four years, SARS-CoV-2, the etiological agent of COVID-19, has been circulating among humans. By the end of the second year, an absence of immunologically naive individuals was observed, attributable to extensive immunization efforts and natural viral exposure. This study focuses on delineating the molecular and biological patterns that facilitate the persistence of SARS-CoV-2, thereby informing predictions on the epidemiological trajectory of COVID-19 toward refining pandemic countermeasures. The aim of this study was to describe the molecular biological patterns identified that contribute to the persistence of the virus in the human population.

MATERIALS AND METHODS

For over three years since the beginning of the COVID-19 pandemic, molecular genetic monitoring of SARS-CoV-2 has been conducted, which included the collection of nasopharyngeal swabs from infected individuals, assessment of viral load, and subsequent whole-genome sequencing.

RESULTS

We discerned dominant genetic lineages correlated with rising disease incidence. We scrutinized amino acid substitutions across SARS-CoV-2 proteins and quantified viral loads in swab samples from patients with emerging COVID-19 variants. Our findings suggest a model of viral persistence characterized by 1) periodic serotype shifts causing substantial diminutions in serum virus-neutralizing activity (> 10-fold), 2) serotype-specific accrual of point mutations in the receptor-binding domain (RBD) to modestly circumvent neutralizing antibodies and enhance receptor affinity, and 3) a gradually increasing amount of virus being shed in mucosal surfaces within a single serotype.

CONCLUSION

This model aptly accounts for the dynamics of COVID-19 incidence in Moscow. For a comprehensive understanding of these dynamics, acquiring population-level data on immune tension and antibody neutralization relative to genetic lineage compositions is essential.

Low booster uptake in cancer patients despite health benefits

Patients with cancer are at increased risk of death from COVID-19 and have reduced immune responses to SARS-CoV2 vaccines, necessitating regular boosters. We performed comprehensive chart reviews, surveys of patients attitudes, serology for SARS-CoV-2 antibodies and T cell receptor (TCR) β sequencing for cellular responses on a cohort of 982 cancer patients receiving active cancer therapy accrued between November-3-2020 and Mar-31-2023. We found that 92 · 3% of patients received the primer vaccine, 70 · 8% received one monovalent booster, but only 30 · 1% received a bivalent booster. Booster uptake was lower under age 50, and among African American or Hispanic patients. Nearly all patients seroconverted after 2+ booster vaccinations (>99%) and improved cellular responses, demonstrating that repeated boosters could overcome poor response to vaccination. Receipt of booster vaccinations was associated with a lower risk of all-cause mortality (HR = 0 · 61, p = 0 · 024). Booster uptake in high-risk cancer patients remains low and strategies to encourage booster uptake are needed.

Immunogenicity of a third dose with mRNA-vaccines in the ChAdOx1-S/BNT162b2 vaccination regimen against SARS-CoV-2 variants

CombiVacS study has demonstrated a strong immune response of the heterologous ChAdOx1-S/BNT162b2 vaccine combination. The primary outcomes of the study were to assess the humoral immune response against SARS-CoV-2, 28 days after a third dose of a mRNA vaccine, in subjects that received a previous prime-boost scheme with ChAdOx1-S/BNT162b2. Secondary outcomes extended the study to 3 and 6 months. The third vaccine dose of mRNA-1273 in naive participants previously vaccinated with ChAdOx1-S/BNT162b2 regimen reached higher neutralizing antibodies titers against the variants of concern Delta and BA.1 lineage of Omicron compared with those receiving a third dose of BNT162b2 at day 28. These differences between BNT162b2 and mRNA-1273 arms were observed against the ancestral variant G614 at day 90. Suboptimal neutralizing response was observed against BQ.1.1, XBB.1.5/XBB.1.9, and JN.1 in a relevant proportion of individuals 180 days after the third dose, even after asymptomatic Omicron breakthrough infections. EudraCT (2021-001978-37); ClinicalTrials.gov (NCT04860739).

Evaluation of Vaccine Strategies among Healthcare Workers during COVID-19 Omicron Outbreak in Taiwan

BACKGROUND/OBJECTIVES

This study aimed to assess the reactogenicity and immunogenicity of various SARS-CoV-2 vaccines and compare their protective effects against COVID-19 among healthcare workers (HCWs) during the Omicron outbreak in Taiwan.

METHODS

Conducted from March 2021 to July 2023, this prospective observational study included healthy HCWs without prior COVID-19 immunization. Participants chose between adenovirus-vectored (AstraZeneca), mRNA (Moderna, BioNTech-Pfizer), and protein-based (Medigen, Novavax) vaccines. Blood samples were taken at multiple points to measure neutralizing antibody (nAb) titers, and adverse events (AEs) were recorded via questionnaires.

RESULTS

Of 710 HCWs, 668 (94.1%) completed three doses, and 290 (40.8%) received a fourth dose during the Omicron outbreak. AEs were more common with AstraZeneca and Moderna vaccines, while Medigen caused fewer AEs. Initial nAb titers were highest with Moderna but waned over time regardless of the vaccine. Booster doses significantly increased nAb titers, with the highest levels observed in Moderna BA1 recipients. The fourth dose significantly reduced COVID-19 incidence, with Moderna BA1 being the most effective.

CONCLUSIONS

Regular booster doses, especially with mRNA and adjuvant-protein vaccines, effectively enhance nAb levels and reduce infection rates, providing critical protection for frontline HCWs during variant outbreaks.

Burden changes in notifiable infectious diseases in Taiwan during the COVID-19 pandemic

Background

This study aimed to assess the impact of the COVID-19 pandemic on the disease burden of Taiwan's notifiable infectious diseases (NIDs). We compared disease burdens between the pandemic and pre-pandemic year of 2020 (with non-pharmaceutical interventions (NPIs)) and 2010 (without NPIs), respectively, to understand the overall pandemic impact on NIDs in Taiwan.

Methods

Forty-three national NIDs were analyzed using the Statistics of Communicable Diseases and Surveillance Report by estimating the premature death and disability via different transmission categories, sex, and age groups. The study evaluated the impact of diseases by assessing the years lost due to death (YLLs), the duration of living with disability (YLDs), and the overall disability-adjusted life years (DALYs) by measuring both the severity of the illness and its duration.

Results

Taiwan recorded 1,577 (2010) and 1,260 (2020) DALYs per million population and lost 43 NIDs, decreasing 317 DALYs per million population. Tuberculosis, HIV/AIDS and acute hepatitis B/D were the leading causes of DALYs, accounting for 89% (2010) and 77% (2020).

Conclusion

Overall, this study provided the first insight of changes in disease burdens in NIDs between pre- and post-COVID-19 based on a nationwide viewpoint for further preventive measures and interventions to be focused on specific diseases by associated health administrations and policies.

Original antigenic sin: A potential double-edged effect for vaccine improvement

Original antigenic sin (OAS) influences the immune response to subsequent infections with related variants following initial pathogen exposure. This phenomenon is characterized by cross-reactivity, which, although it may worsen infections, also provides a degree of protection against immune evasion caused by variations. This paradox complicates the development of creating universal vaccinations, as they frequently show diminished effectiveness against these emerging variants. This review aims to elucidate the diverse impacts of OAS on the immune response to various infections, emphasizing the complicated balance between beneficial and harmful outcomes. Moreover, we evaluate the influence of adjuvants and other variables on the extent of OAS, hence affecting the effectiveness of vaccines. Understanding the mechanisms of OAS that cause persistent infections and evasion of the immune system is crucial for the developing innovative vaccines. And it has significant potential for clinical applications.

Proton pump inhibitors associated with severe COVID-19 among two-dose but not three-dose vaccine recipients

BACKGROUND AND AIM

Proton pump inhibitors (PPIs) may increase the risk of COVID-19 among non-vaccinated subjects via various mechanisms, including gut dysbiosis. We aimed to investigate whether PPIs also affect the clinical outcomes of COVID-19 among vaccine recipients.

METHODS

This was a territory-wide cohort study of 3 272 286 vaccine recipients (aged ≥ 18 years) of ≥ 2 doses of either BNT162b2 or CoronaVac. Exclusion criteria included prior gastrointestinal surgery, immunocompromised status, and prior COVID-19. The primary outcome was COVID-19, and secondary outcomes included COVID-19-related hospitalization and severe infection (composite of intensive care unit admission, ventilatory support, and/or death). Covariates include age, sex, the Charlson Comorbidity Index, comorbidities, and concomitant medication use. Subjects were followed from index date (first dose of vaccination) until outcome occurrence, death, additional dose of vaccination, or March 31, 2022. Exposure was pre-vaccination PPI use (any prescription within 90 days before the index date). Propensity score (PS) matching and a Poisson regression model were used to estimate the adjusted incidence rate ratio (aIRR) of outcomes with PPI use.

RESULTS

Among 439 154 PS-matched two-dose vaccine recipients (mean age: 65.3 years; male: 45.7%) with a median follow-up of 6.8 months (interquartile range: 2.6-7.9), PPI exposure was associated with a higher risk of COVID-19 (aIRR: 1.08; 95% confidence interval [95% CI]: 1.05-1.10), hospitalization (aIRR: 1.20; 95% CI: 1.08-1.33), and severe infection (aIRR: 1.57; 95% CI: 1.24-1.98). Among 188 360 PS-matched three-dose vaccine recipients (mean age: 62.5 years; male: 49.0%; median follow-up: 9.1 months [interquartile range: 8.0-10.9]), PPIs were associated with higher infection risk (aIRR: 1.11; 95% CI: 1.08-1.15) but not other outcomes.

CONCLUSIONS

Although PPI use was associated with a higher COVID-19 risk, severe infection was limited to two-dose but not three-dose vaccine recipients.

Immunogenicity, reactogenicity, and safety of a second booster with BNT162b2 or full-dose mRNA-1273: A randomized VACCELERATE trial in adults aged ≥75 years (EU-COVAT-1-AGED Part B)

OBJECTIVES

To assess the safety and immunogenicity of a fourth vaccination (second booster) in individuals aged ≥75 years.

METHODS

Participants were randomized to BNT162b2 (Comirnaty, 30 µg) or messenger RNA (mRNA)-1273 (Spikevax, 100 µg). The primary end point was the rate of two-fold antibody titer increase 14 days after vaccination, targeting the receptor binding domain (RBD) region of wild-type SARS-CoV-2. The secondary end points included changes in neutralizing activity against wild-type and 25 variants. Safety was assessed by monitoring solicited adverse events (AEs) for 7 days.

RESULTS

A total of 269 participants (mean age 81 years, mRNA-1273 n = 135/BNT162b2 n = 134) were included. Two-fold anti-RBD immunoglobulin (Ig) G titer increase was achieved by 101 of 129 (78%) and 116 of 133 (87%) subjects in the BNT162b2 and the mRNA-1273 group, respectively (P = 0.054). A second booster of mRNA-1273 provided higher anti-RBD IgG geometric mean titer: 21.326 IU/mL (95% confidence interval: 18.235-24.940) vs BNT162b2: 15.181 IU/mL (95% confidence interval: 13.172-17.497). A higher neutralizing activity was noted for the mRNA-1273 group. The most frequent AE was pain at the injection site (51% in mRNA-1273 and 48% in BNT162b2). Participants in the mRNA-1273 group had less vaccine-related AEs (30% vs 39%).

CONCLUSIONS

A second booster of either BNT162b2 or mRNA-1273 provided substantial IgG increase. Full-dose mRNA-1273 provided higher IgG levels and neutralizing capacity against SARS-CoV-2, with similar safety profile for subjects of advanced age.

Waning Humoral Immune Response Following the Third and Fourth SARS-COV-2 Vaccine: A Cohort Study in Healthcare Workers

BACKGROUND

This study is aimed at providing information about the timing of booster doses and antibody kinetics in healthcare workers.

METHODS

This research extends a prospective cohort study conducted at Dokuz Eylul University Hospital in Turkey, covering the period from March 2021 to December 2021. During this timeframe, the antibody levels of the health workers were measured at four different time points. The associations of antibody levels with gender, age, occupation, body mass index (BMI), chronic disease, and smoking were analyzed.

RESULTS

There was a significant difference between antibody levels in all four blood draws (p < 0.001). Antibody levels decreased in both those vaccinated with BNT162b2 (p < 0.001) and those vaccinated with CoronaVac (p = 0.002) until the fourth blood draw. There was a significant difference between those vaccinated with one and two doses of booster BNT162b2 before the third blood draw (p < 0.001), which continued at the fourth blood draw (p < 0.001). The antibody levels of those with an interval of 41-50 days between two vaccinations decreased significantly at the fourth blood draw (p < 0.001).

CONCLUSIONS

This study provides insight into the dynamics and persistence of antibody response after additional COVID-19 vaccine doses among healthcare workers. The longer the interval between booster doses may result in greater antibody levels being maintained over time, allowing for longer durations of protection.

Viral vector-based therapeutic HPV vaccines

Replication-defective viral vector vaccines have several advantages over conventional subunit vaccines, including potent antibody responses, cellular responses critical for eliminating pathogen-infected cells, and the induction of highly immunogenic and durable immune responses without adjuvants. The Human papillomavirus (HPV), a microorganism with over 200 genotypes, plays a crucial role in inducing human tumors, with the majority of HPV-related malignancies expressing HPV proteins. Tumors associated with HPV infection, most of which result from HPV16 infection, include those affecting the cervix, anus, vagina, penis, vulva, and oropharynx. In recent years, the development of therapeutic HPV vaccines utilizing viral vectors for the treatment of premalignant lesions or tumors caused by HPV infection has experienced rapid growth, with numerous research pipelines currently underway. Simultaneously, screening for optimal antigens requires more basic research and more optimized methods. In terms of preclinical research, we present the various models used to assess vaccine efficacy, highlighting their respective advantages and disadvantages. Further, we present current research status of therapeutic vaccines using HPV viral vectors, especially the indications, initial efficacy, combination drugs, etc. In general, this paper summarizes current viral vector therapeutic HPV vaccines in terms of HPV infection, antigen selection, vectors, efficacy evaluation, and progress in clinical trials.

The Novavax Heterologous Coronavirus Disease 2019 Booster Demonstrates Lower Reactogenicity Than Messenger RNA: A Targeted Review

Coronavirus disease 2019 (COVID-19) continues to be a global health concern, and booster doses are necessary for maintaining vaccine-mediated protection, limiting the spread of severe acute respiratory syndrome coronavirus 2. Despite multiple COVID-19 vaccine options, global booster uptake remains low. Reactogenicity, the occurrence of adverse local/systemic side effects, plays a crucial role in vaccine uptake and acceptance, particularly for booster doses. We conducted a targeted review of the reactogenicity of authorized/approved messenger RNA (mRNA) and protein-based vaccines demonstrated by clinical trials and real-world evidence. It was found that mRNA-based boosters show a higher incidence and an increased severity of reactogenicity compared with the Novavax protein-based COVID-19 vaccine (NVX-CoV2373). In a recent study from the National Institute of Allergy and Infectious Diseases, the incidence of pain/tenderness, swelling, erythema, fatigue/malaise, headache, muscle pain, or fever was higher in individuals boosted with BNT162b2 (0.4% to 41.6% absolute increase) or mRNA-1273 (5.5% to 55.0% absolute increase) compared with NVX-CoV2373. Evidence suggests that NVX-CoV2373, when utilized as a heterologous booster, demonstrates less reactogenicity compared with mRNA vaccines, which, if communicated to hesitant individuals, may strengthen booster uptake rates worldwide. Clinical Trials Registration NCT04889209.

Age differentially impacts adaptive immune responses induced by adenoviral versus mRNA vaccines against COVID-19

Adenoviral and mRNA vaccines encoding the viral spike (S) protein have been deployed globally to contain severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Older individuals are particularly vulnerable to severe infection, probably reflecting age-related changes in the immune system, which can also compromise vaccine efficacy. It is nonetheless unclear to what extent different vaccine platforms are impacted by immunosenescence. Here, we evaluated S protein-specific immune responses elicited by vaccination with two doses of BNT162b2 or ChAdOx1-S and subsequently boosted with a single dose of BNT162b2 or mRNA-1273, comparing age-stratified participants with no evidence of previous infection with SARS-CoV-2. We found that aging profoundly compromised S protein-specific IgG titers and further limited S protein-specific CD4+ and CD8+ T cell immunity as a probable function of progressive erosion of the naive lymphocyte pool in individuals vaccinated initially with BNT162b2. Our results demonstrate that primary vaccination with ChAdOx1-S and subsequent boosting with BNT162b2 or mRNA-1273 promotes sustained immunological memory in older adults and potentially confers optimal protection against coronavirus disease 2019.

Real-World Effectiveness of a Third Dose of mRNA-1273 Versus BNT162b2 on Inpatient and Medically Attended COVID-19 Among Immunocompromised US Adults

INTRODUCTION

Recent data have shown elevated infection rates in several subpopulations at risk of SARS-CoV-2 infection and COVID-19, including immunocompromised (IC) individuals. Previous research suggests that IC persons have reduced risks of hospitalization and medically attended COVID-19 with two doses of mRNA-1273 (SpikeVax; Moderna) compared to two doses of BNT162b2 (Comirnaty; Pfizer/BioNTech). The main objective of this retrospective cohort study was to compare real-world effectiveness of third doses of mRNA-1273 versus BNT162b2 at multiple time points on occurrence of COVID-19 hospitalization and medically attended COVID-19 among IC adults in the United States (US).

METHODS

This retrospective, observational comparative effectiveness study identified patients from the US HealthVerity database from December 11, 2020, through August 31, 2022. Medically attended SARS-CoV-2 infections and hospitalizations were assessed following a three-dose mRNA-1273 versus BNT162b2 regimen. Inverse probability weighting was applied to balance baseline confounders between vaccine groups. Relative risk (RR) and risk difference were calculated for subgroup and sensitivity analyses using a non-parametric method.

RESULTS

In propensity score-adjusted analyses, receiving mRNA-1273 vs. BNT162b2 as third dose was associated with 32.4% (relative risk 0.676; 95% confidence interval 0.506-0.887), 29.3% (0.707; 0.573-0.858), and 23.4% (0.766; 0.626-0.927) lower risk of COVID-19 hospitalization after 90, 180, and 270 days, respectively. Corresponding reductions in medically attended COVID-19 were 8.4% (0.916; 0.860-0.976), 6.4% (0.936; 0.895-0.978), and 2.4% (0.976; 0.935-1.017), respectively.

CONCLUSIONS

Our findings suggest a third dose of mRNA-1273 is more effective than a third dose of BNT162b2 in preventing COVID-19 hospitalization and breakthrough medically attended COVID-19 among IC adults in the US.

Comprehensive Review of COVID-19: Epidemiology, Pathogenesis, Advancement in Diagnostic and Detection Techniques, and Post-Pandemic Treatment Strategies

At present, COVID-19 remains a public health concern due to the ongoing evolution of SARS-CoV-2 and its prevalence in particular countries. This paper provides an updated overview of the epidemiology and pathogenesis of COVID-19, with a focus on the emergence of SARS-CoV-2 variants and the phenomenon known as 'long COVID'. Meanwhile, diagnostic and detection advances will be mentioned. Though many inventions have been made to combat the COVID-19 pandemic, some outstanding ones include multiplex RT-PCR, which can be used for accurate diagnosis of SARS-CoV-2 infection. ELISA-based antigen tests also appear to be potential diagnostic tools to be available in the future. This paper also discusses current treatments, vaccination strategies, as well as emerging cell-based therapies for SARS-CoV-2 infection. The ongoing evolution of SARS-CoV-2 underscores the necessity for us to continuously update scientific understanding and treatments for it.

Statistical considerations for the platform trial in COVID-19 vaccine priming and boosting

The Platform trial In COVID-19 priming and BOOsting (PICOBOO) is a multi-site, adaptive platform trial designed to generate evidence of the immunogenicity, reactogenicity, and cross-protection of different booster vaccination strategies against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and its variants, specific for the Australian context. The PICOBOO trial randomises participants to receive one of three COVID-19 booster vaccine brands (Pfizer, Moderna, Novavax) available for use in Australia, where the vaccine brand subtypes vary over time according to the national vaccine roll out strategy, and employs a Bayesian hierarchical modelling approach to efficiently borrow information across consecutive booster doses, age groups and vaccine brand subtypes. Here, we briefly describe the PICOBOO trial structure and report the statistical considerations for the estimands, statistical models and decision making for trial adaptations. This paper should be read in conjunction with the PICOBOO Core Protocol and PICOBOO Sub-Study Protocol 1: Booster Vaccination. PICOBOO was registered on 10 February 2022 with the Australian and New Zealand Clinical Trials Registry ACTRN12622000238774.

Safety, reactogenicity, and immunogenicity of Ad26.COV2.S as homologous or heterologous COVID-19 booster vaccination: Results of a randomized, double-blind, phase 2 trial

COVID-19 vaccine boosters may optimize durability of protection against variants of concern (VOCs). In this randomized, double-blind, phase 2 trial, participants received 3 different dose levels of an Ad26.COV2.S booster (5 × 1010 vp [viral particles], 2.5 × 1010 vp, or 1 × 1010 vp) ≥6 months post-primary vaccination with either single-dose Ad26.COV2.S (homologous boost; n = 774) or 2-dose BNT162b2 (heterologous boost; n = 758). Primary endpoints were noninferiority of neutralizing antibody responses at Day 15 post-boost versus Day 29 post-primary vaccination. Secondary endpoints included reactogenicity/safety and neutralizing antibody responses to VOCs. All primary endpoints passed prespecified hierarchical noninferiority criteria by Day 15 post-boost. Geometric mean increases in neutralizing antibody titers against the D614G reference strain ranged from 5.5 to 6.8 at Day 15 for homologous boosting and 12.6 to 22.0 for heterologous boosting. For VOCs, heterologous boosting elicited higher neutralizing antibody responses than homologous boosting. Neutralizing antibody responses were dose-dependent and durable for ≥6 months post-boost. More solicited systemic adverse events occurred following heterologous versus homologous boosting. Trial Registration:ClinicalTrials.gov Identifier: NCT04999111.

Reactogenicity Differences between Adjuvanted, Protein-Based and Messenger Ribonucleic Acid (mRNA)-Based COVID-19 Vaccines

Participants in studies investigating COVID-19 vaccines commonly report reactogenicity events, and concerns about side effects may lead to a reluctance to receive updated COVID-19 vaccinations. A real-world, post hoc analysis, observational 2019nCoV-406 study was conducted to examine reactogenicity within the first 2 days after vaccination with either a protein-based vaccine (NVX-CoV2373) or an mRNA vaccine (BNT162b2 or mRNA-1273) in individuals who previously completed a primary series. Propensity score adjustments were conducted to address potential confounding. The analysis included 1130 participants who received a booster dose of NVX-CoV2373 (n = 303) or an mRNA vaccine (n = 827) during the study period. Within the first 2 days after vaccination, solicited systemic reactogenicity events (adjusted) were reported in 60.5% of participants who received NVX-CoV2373 compared with 84.3% of participants who received an mRNA vaccine; moreover, 33.9% and 61.4%, respectively, reported ≥3 systemic reactogenicity symptoms. The adjusted mean (95% CI) number of systemic symptoms was 1.8 (1.6-2.0) and 3.2 (3.0-3.4), respectively. Local reactogenicity events (adjusted) were reported in 73.4% and 91.7% of participants who received NVX-CoV2373 and mRNA vaccines, respectively; the adjusted mean (95% CI) number of local symptoms was 1.5 (1.33-1.61) and 2.4 (2.31-2.52), respectively. These results support the use of adjuvanted, protein-based NVX-CoV2373 as an immunization option with lower reactogenicity than mRNAs.

Equal Maintenance of Anti-SARS-CoV-2 Antibody Levels Induced by Heterologous and Homologous Regimens of the BNT162b2, ChAdOx1, CoronaVac and Ad26.COV2.S Vaccines: A Longitudinal Study Up to the 4th Dose of Booster

Several technological approaches have been used to develop vaccines against COVID-19, including those based on inactivated viruses, viral vectors, and mRNA. This study aimed to monitor the maintenance of anti-SARS-CoV-2 antibodies in individuals from Brazil according to the primary vaccination regimen, as follows: BNT162b2 (group 1; 22) and ChAdOx1 (group 2; 18). Everyone received BNT162b2 in the first booster while in the second booster CoronaVac, Ad26.COV2.S, or BNT162b2. Blood samples were collected from 2021 to 2023 to analyze specific RBD (ELISA) and neutralizing antibodies (PRNT50). We observed a progressive increase in anti-RBD and neutralizing antibodies in each subsequent dose, remaining at high titers until the end of follow-up. Group 1 had higher anti-RBD antibody titers than group 2 after beginning the primary regimen, with significant differences after the 2nd and 3rd doses. Group 2 showed a more expressive increase after the first booster with BNT162B2 (heterologous booster). Group 2 also presented high levels of neutralizing antibodies against the Gamma and Delta variants until five months after the second booster. In conclusion, the circulating levels of anti-RBD and neutralizing antibodies against the two variants of SARS-CoV-2 were durable even five months after the 4th dose, suggesting that periodic booster vaccinations (homologous or heterologous) induced long-lasting immunity.