Effectiveness of COVID-19 Pfizer-BioNTech (BNT162b2) mRNA vaccination in adolescents aged 12-17 years: A systematic review and meta-analysis.

The rapid emergence of COVID-19 variants of concern (VOCs) has hindered vaccine uptake. To inform policy, we investigated the effectiveness of the BNT162b2 vaccination among adolescents against symptomatic and severe COVID-19 diseases using mostly real-world data (15 studies). We searched international databases until May 2022 and used Cochrane's risk of bias tools for critical appraisal. Random effects models were used to examine overall vaccine effectiveness (VE) across studies (general inverse-variance) and the effect of circulating VOCs on VE (log relative ratio and VE). Meta-regression assessed the effect of age and time on VE (restricted-maximum likelihood). BNT162b2 VE against PCR-confirmed SARS-CoV-2 was 82.7% (95%CI: 78.37-87.31%). VE was higher for severe (88%) than non-severe (35%) outcomes and declining over time improved following booster dose in omicron era [73%(95%CI:65-81%)]. Fully vaccinated adolescents are protected from COVID-19 circulating VOCs by BNT162b2 especially for the need of critical care or life support.

Systematic review and meta-analysis of myocarditis and pericarditis in adolescents following COVID-19 BNT162b2 vaccination.

Myocarditis and pericarditis are frequent complications of COVID-19, but have also been reported following vaccination against COVID-19 in adolescents. To build vaccine confidence and inform policy, we characterized the incidence of myocarditis/pericarditis in adolescents following BNT162b2 vaccination and explored the association with dose and sex. We searched national and international databases for studies reporting the incidence of myocarditis/pericarditis following BNT162b2 vaccination as the primary endpoint. The intra-study risk of bias was appraised, and random-effects meta-analyses were performed to estimate the pooled incidence by dose stratified by sex. The pooled incidence of myocarditis/pericarditis was 4.5 (95%CI: 3.14-6.11) per 100,000 vaccinations across all doses. Compared to dose 1, the risk was significantly higher after dose 2 (RR: 8.62, 95%CI: 5.71-13.03). However, adolescents experienced a low risk after a booster dose than after dose 2 (RR: 0.06; 95%CI: 0.04-0.09). Males were approximately seven times (RR: 6.66, 95%CI: 4.77-4.29) more likely than females to present myocarditis/pericarditis. In conclusion, we found a low frequency of myocarditis/pericarditis after BNT162b2, which occurred predominantly after the second dose in male adolescents. The prognosis appears to be favorable, with full recovery in both males and females. National programs are recommended to adopt the causality framework to reduce overreporting, which undercuts the value of the COVID-19 vaccine on adolescent life, as well as to extend the inter-dose interval policy, which has been linked to a lower frequency of myocarditis/pericarditis.

Wastewater-based SARS-CoV-2 airport surveillance: key trends at the Cape Town International Airport.

Monitoring of SARS-CoV-2 RNA in wastewater has revealed the role of mobility in the transmission of coronavirus disease (COVID-19), and the surveillance of airport wastewater in cities across the world has demonstrated how travel entry points can give an indication of trends in transmission. This study undertook wastewater surveillance at the Cape Town International Airport (CTIA) to assess the use of a WBE approach to provide supplementary information on the presence of COVID-19 at a key air travel entry point in South Africa. Grab wastewater samples (n = 55) were collected from the CTIA wastewater pump station and analysed using quantitative real-time polymerase chain reaction (qRT-PCR) method. The study found a correlation between the wastewater data and clinical cases reported in the City of Cape Town during various time periods and during the peak of a COVID-19 wave. Highly elevated viral loads in the wastewater were observed at times there was increased mobility through the airport. The study also revealed elevated viral load levels at the airport despite the stricter restrictions and through the lower restrictions. The study findings indicate wastewater surveillance and airports can provide supplementary information to airport authorities to assess the impacts of imposed travel restrictions.

Immunogenicity and reactogenicity of COVID-19 Pfizer-BioNTech (Bnt162b2) mRNA vaccination in immunocompromised adolescents and young adults: a systematic review and meta-analyses.

BACKGROUND: This study aimed to evaluate the safety and effectiveness of the BNT162b2 vaccine in immunocompromised adolescents and young adults. RESEARCH DESIGN AND METHODS: The study conducted a meta-analysis of post-marketing studies examining BNT162b2 vaccination efficacy and safety among immunocompromised adolescents and young adults worldwide. The review included nine studies and 513 individuals aged between 12 and 24.3 years. The study used a random effect model to estimate pooled proportions, log relative risk, and mean difference, and assessed heterogeneity using the I2 test. The study also examined publication bias using Egger's regression and Begg's rank correlation and assessed bias risk using ROBINS-I. RESULTS: The pooled proportions of combined local and systemic reactions after the first and second doses were 30% and 32%, respectively. Adverse events following immunization (AEFI) were most frequent in rheumatic diseases (40%) and least frequent in cystic fibrosis (27%), although hospitalizations for AEFIs were rare. The pooled estimations did not show a statistically significant difference between immunocompromised individuals and healthy controls for neutralizing antibodies, measured IgG, or vaccine effectiveness after the primary dose. However, the evidence quality is low to moderate due to a high risk of bias, and no study could rule out the risk of selection bias, ascertainment bias, or selective outcome reporting. CONCLUSIONS: This study provides preliminary evidence that the BNT162b2 vaccine is safe and effective in immunocompromised adolescents and young adults, but with low to moderate evidence quality due to bias risk. The study calls for improved methodological quality in studies involving specific populations.

Vascular thrombosis after single dose Ad26.COV2.S vaccine in healthcare workers in South Africa: open label, single arm, phase 3B study (Sisonke study).

Objective: To assess the rates of vascular thrombotic adverse events in the first 35 days after one dose of the Ad26.COV2.S vaccine (Janssen/Johnson & Johnson) in healthcare workers in South Africa and to compare these rates with those observed in the general population. Design: Open label, single arm, phase 3B study. Setting: Sisonke study, South Africa, 17 February to 15 June 2021. Participants: The Sisonke cohort of 477 234 healthcare workers, aged ≥18 years, who received one dose of the Ad26.COV2.S vaccine. Main outcome measures: Observed rates of venous arterial thromboembolism and vaccine induced immune thrombocytopenia and thrombosis in individuals who were vaccinated, compared with expected rates, based on age and sex specific background rates from the Clinical Practice Research Datalink GOLD database (database of longitudinal routinely collected electronic health records from UK primary care practices using Vision general practice patient management software). Results: Most of the study participants were women (74.9%) and median age was 42 years (interquartile range 33-51). Twenty nine (30.6 per 100 000 person years, 95% confidence interval 20.5 to 44.0) vascular thrombotic events occurred at a median of 14 days (7-29) after vaccination. Of these 29 participants, 93.1% were women, median age 46 (37-55) years, and 51.7% had comorbidities. The observed to expected ratios for cerebral venous sinus thrombosis with thrombocytopenia and pulmonary embolism with thrombocytopenia were 10.6 (95% confidence interval 0.3 to 58.8) and 1.2 (0.1 to 6.5), respectively. Because of the small number of adverse events and wide confidence intervals, no conclusions were drawn between these estimates and the expected incidence rates in the population. Conclusions: Vaccine induced immune thrombocytopenia and thrombosis after one dose of the Ad26.COV2.S vaccine was found in only a few patients in this South African population of healthcare workers. These findings are reassuring if considered in terms of the beneficial effects of vaccination against covid-19 disease. These data support the continued use of this vaccine, but surveillance is recommended to identify other incidences of venous and arterial thromboembolism and to improve confidence in the data estimates. Trial registration: ClinicalTrials.gov NCT04838795.

The Future of Epidemic and Pandemic Vaccines to Serve Global Public Health Needs.

This Review initiates a wide-ranging discussion over 2023 by selecting and exploring core themes to be investigated more deeply in papers submitted to the Vaccines Special Issue on the "Future of Epidemic and Pandemic Vaccines to Serve Global Public Health Needs". To tackle the SARS-CoV-2 pandemic, an acceleration of vaccine development across different technology platforms resulted in the emergency use authorization of multiple vaccines in less than a year. Despite this record speed, many limitations surfaced including unequal access to products and technologies, regulatory hurdles, restrictions on the flow of intellectual property needed to develop and manufacture vaccines, clinical trials challenges, development of vaccines that did not curtail or prevent transmission, unsustainable strategies for dealing with variants, and the distorted allocation of funding to favour dominant companies in affluent countries. Key to future epidemic and pandemic responses will be sustainable, global-public-health-driven vaccine development and manufacturing based on equitable access to platform technologies, decentralised and localised innovation, and multiple developers and manufacturers, especially in low- and middle-income countries (LMICs). There is talk of flexible, modular pandemic preparedness, of technology access pools based on non-exclusive global licensing agreements in exchange for fair compensation, of WHO-supported vaccine technology transfer hubs and spokes, and of the creation of vaccine prototypes ready for phase I/II trials, etc. However, all these concepts face extraordinary challenges shaped by current commercial incentives, the unwillingness of pharmaceutical companies and governments to share intellectual property and know-how, the precariousness of building capacity based solely on COVID-19 vaccines, the focus on large-scale manufacturing capacity rather than small-scale rapid-response innovation to stop outbreaks when and where they occur, and the inability of many resource-limited countries to afford next-generation vaccines for their national vaccine programmes. Once the current high subsidies are gone and interest has waned, sustaining vaccine innovation and manufacturing capability in interpandemic periods will require equitable access to vaccine innovation and manufacturing capabilities in all regions of the world based on many vaccines, not just "pandemic vaccines". Public and philanthropic investments will need to leverage enforceable commitments to share vaccines and critical technology so that countries everywhere can establish and scale up vaccine development and manufacturing capability. This will only happen if we question all prior assumptions and learn the lessons offered by the current pandemic. We invite submissions to the special issue, which we hope will help guide the world towards a global vaccine research, development, and manufacturing ecosystem that better balances and integrates scientific, clinical trial, regulatory, and commercial interests and puts global public health needs first.

Association between regular physical activity and the protective effect of vaccination against SARS-CoV-2 in a South African case-control study.

BACKGROUND: Both vaccination and physical activity have been shown to independently decrease the likelihood of severe COVID-19 infection. OBJECTIVE: To assess the association between regular physical activity and vaccination against COVID-19 among healthcare workers. METHODS: A test negative case-control study design was used to estimate the risk of having an associated COVID-19-related hospital admission, among individuals who were unvaccinated compared with those who were fully vaccinated with Ad26.COV2.S (>28 days after a single dose). 196 444 participant tests were stratified into three measured physical activity subgroups with low, moderate and high activity, to test the hypothesis that physical activity is an effect modifier on the relationship between vaccination and hospitalisation. RESULTS: Vaccine effectiveness against a COVID-19-related admission among vaccinated individuals within the low activity group was 60.0% (95% CI 39.0 to 73.8), 72.1% (95% CI 55.2 to 82.6) for the moderate activity group, and 85.8% (95% CI 74.1 to 92.2) for the high activity group. Compared with individuals with low activity levels, vaccinated individuals with moderate and high activity levels had a 1.4 (95% CI 1.36 to 1.51) and 2.8 (95% CI 2.35 to 3.35) times lower risk of COVID-19 admission, respectively (p value <0.001 for both groups). CONCLUSIONS: Regular physical activity was associated with improved vaccine effectiveness against COVID-19 hospitalisation, with higher levels of physical activity associated with greater vaccine effectiveness. Physical activity enhances vaccine effectiveness against severe COVID-19 outcomes and should be encouraged by greater public health messaging.

Novavax NVX-COV2373 triggers neutralization of Omicron sub-lineages.

The SARS-CoV-2 Omicron (B.1.1.529) Variant of Concern (VOC) and its sub-lineages (including BA.2, BA.4, BA.5, BA.2.12.1) contain spike mutations that confer high level resistance to neutralizing antibodies induced by vaccination with ancestral spike or infection with previously circulating variants. The NVX-CoV2373 vaccine, a protein nanoparticle vaccine containing the ancestral spike sequence, has value in countries with constrained cold-chain requirements. Here we report neutralizing titers following two or three doses of NVX-CoV2373. We show that after two doses, Omicron sub-lineages BA.1 and BA.4/BA.5 were resistant to neutralization by 72% (21/29) and 59% (17/29) of samples respectively. However, after a third dose of NVX-CoV2373, we observed high titers against Omicron BA.1 (GMT: 1,197) and BA.4/BA.5 (GMT: 582), with responses similar in magnitude to those triggered by three doses of an mRNA vaccine. These data are of particular relevance as BA.4/BA.5 is dominating in multiple locations, and highlight the potential utility of the NVX-CoV2373 vaccine as a booster in resource-limited environments.

Rapid Development of an Integrated Network Infrastructure to Conduct Phase 3 COVID-19 Vaccine Trials.

Importance: The COVID-19 pandemic has caused millions of infections and deaths and resulted in unprecedented international public health social and economic crises. As SARS-CoV-2 spread across the globe and its impact became evident, the development of safe and effective vaccines became a priority. Outlining the processes used to establish and support the conduct of the phase 3 randomized clinical trials that led to the rapid emergency use authorization and approval of several COVID-19 vaccines is of major significance for current and future pandemic response efforts. Observations: To support the rapid development of vaccines for the US population and the rest of the world, the National Institute of Allergy and Infectious Diseases established the COVID-19 Prevention Network (CoVPN) to assist in the coordination and implementation of phase 3 efficacy trials for COVID-19 vaccine candidates and monoclonal antibodies. By bringing together multiple networks, CoVPN was able to draw on existing clinical and laboratory infrastructure, community partnerships, and research expertise to quickly pivot clinical trial sites to conduct COVID-19 vaccine trials as soon as the investigational products were ready for phase 3 testing. The mission of CoVPN was to operationalize phase 3 vaccine trials using harmonized protocols, laboratory assays, and a single data and safety monitoring board to oversee the various studies. These trials, while staggered in time of initiation, overlapped in time and course of conduct and ultimately led to the successful completion of multiple studies and US Food and Drug Administration-licensed or -authorized vaccines, the first of which was available to the public less than 1 year from the discovery of the virus. Conclusions and Relevance: This Special Communication describes the design, geographic distribution, and underlying principles of conduct of these efficacy trials and summarizes data from 136 382 prospectively followed-up participants, including more than 2500 with documented COVID-19. These successful efforts can be replicated for other important research initiatives and point to the importance of investments in clinical trial infrastructure integral to pandemic preparedness.

Immune correlates analysis of the ENSEMBLE single Ad26.COV2.S dose vaccine efficacy clinical trial.

Measuring immune correlates of disease acquisition and protection in the context of a clinical trial is a prerequisite for improved vaccine design. We analysed binding and neutralizing antibody measurements 4 weeks post vaccination as correlates of risk of moderate to severe-critical COVID-19 through 83 d post vaccination in the phase 3, double-blind placebo-controlled phase of ENSEMBLE, an international randomized efficacy trial of a single dose of Ad26.COV2.S. We also evaluated correlates of protection in the trial cohort. Of the three antibody immune markers we measured, we found most support for 50% inhibitory dilution (ID50) neutralizing antibody titre as a correlate of risk and of protection. The outcome hazard ratio was 0.49 (95% confidence interval 0.29, 0.81; P = 0.006) per 10-fold increase in ID50; vaccine efficacy was 60% (43%, 72%) at non-quantifiable ID50 (<2.7 IU50 ml-1) and increased to 89% (78%, 96%) at ID50 = 96.3 IU50 ml-1. Comparison of the vaccine efficacy by ID50 titre curves for ENSEMBLE-US, the COVE trial of the mRNA-1273 vaccine and the COV002-UK trial of the AZD1222 vaccine supported the ID50 titre as a correlate of protection across trials and vaccine types.

Using Wastewater Surveillance to Compare COVID-19 Outbreaks during the Easter Holidays over a 2-Year Period in Cape Town, South Africa.

Wastewater surveillance of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has shown to be an important approach to determine early outbreaks of infections. Wastewater-based epidemiology (WBE) is regarded as a complementary tool for monitoring SARS-CoV-2 trends in communities. In this study, the changes in the SARS-CoV-2 RNA levels in wastewater during Easter holidays in 2021 and 2022 in the City of Cape Town were monitored over nine weeks. Our findings showed a statistically significant difference in the SARS-CoV-2 RNA viral load between the study weeks over the Easter period in 2021 and 2022, except for study week 1 and 4. During the Easter week, 52% of the wastewater treatment plants moved from the lower (low viral RNA) category in 2021 to the higher (medium to very high viral RNA) categories in 2022. As a result, the median SARS-CoV-2 viral loads where higher during the Easter week in 2022 than Easter week in 2021 (p = 0.0052). Mixed-effects model showed an association between the SARS-CoV-2 RNA viral loads and Easter week over the Easter period in 2021 only (p < 0.01). The study highlights the potential of WBE to track outbreaks during the holiday period.

Impact of SARS-CoV-2 exposure history on the T cell and IgG response.

Multiple severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) exposures, from infection or vaccination, can potently boost spike antibody responses. Less is known about the impact of repeated exposures on T cell responses. Here, we compare the prevalence and frequency of peripheral SARS-CoV-2-specific T cell and immunoglobulin G (IgG) responses in 190 individuals with complex SARS-CoV-2 exposure histories. As expected, an increasing number of SARS-CoV-2 spike exposures significantly enhances the magnitude of IgG responses, while repeated exposures improve the number of T cell responders but have less impact on SARS-CoV-2 spike-specific T cell frequencies in the circulation. Moreover, we find that the number and nature of exposures (rather than the order of infection and vaccination) shape the spike immune response, with spike-specific CD4 T cells displaying a greater polyfunctional potential following hybrid immunity compared with vaccination only. Characterizing adaptive immunity from an evolving viral and immunological landscape may inform vaccine strategies to elicit optimal immunity as the pandemic progress.

Safety of COVID-19 Pfizer-BioNtech (BNT162b2) mRNA vaccination in adolescents aged 12-17 years: A systematic review and meta-analysis.

The COVID-19 pandemic has severely affected adolescents. Safe and effective vaccines are pivotal tools in controlling this pandemic. We reviewed the safety profile of the BNT162b2 COVID-19 vaccine in adolescents using mostly real-world data to assist decision-making. We used random-effects model meta-analysis to derive pooled rates of single or grouped adverse events following immunization (AEFI) after each primary and booster dose, as well as after combining all doses. Reporting on over one million participants with safety data were included. The most-reported local and systemic AEFIs were pain/swelling/erythema/redness and fatigue/headache/myalgia, respectively. AESIs were rarely reported but were more frequent after the second dose than they were after the first and the booster doses. Health impact was less common among adolescents after receiving BNT162b2 vaccine. Rare life-threatening AEFIs were reported across all doses in real-world studies. Our findings highlight the significance of enhancing national and regional vaccination programs to ensure public confidence.

Delineating the Spread and Prevalence of SARS-CoV-2 Omicron Sublineages (BA.1-BA.5) and Deltacron Using Wastewater in the Western Cape, South Africa.

This study was one of the first to detect Omicron sublineages BA.4 and BA.5 in wastewater from South Africa. Spearman rank correlation analysis confirmed a strong positive correlation between severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) viral RNA in wastewater samples and clinical cases (r = 0.7749, P < .0001). SARS-CoV-2 viral load detected in wastewater, resulting from the Delta-driven third wave, was significantly higher than during the Omicron-driven fourth wave. Whole-genome sequencing confirmed presence of Omicron lineage defining mutations in wastewater with the first occurrence reported 23 November 2021 (BA.1 predominant). The variant spread rapidly, with prevalence of Omicron-positive wastewater samples rising to >80% by 10 January 2022 with BA.2 as the predominant sublineage by 10 March 2022, whilst on 18 April 2022 BA.4 and BA.5 were detected in selected wastewater sites. These findings demonstrate the value of wastewater-based epidemiology to monitor the spatiotemporal spread and potential origin of new Omicron sublineages.

Immunogenicity of Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) Infection and Ad26.CoV2.S Vaccination in People Living With Human Immunodeficiency Virus (HIV).

BACKGROUND: People living with HIV (PLWH) have been reported to have a higher risk of more severe COVID-19 disease and death. We assessed the ability of the Ad26.CoV2.S vaccine to elicit neutralizing activity against the Delta variant in PLWH relative to HIV-negative individuals. We also examined effects of HIV status and suppression on Delta neutralization response in SARS-CoV-2-infected unvaccinated participants. METHODS: We enrolled participants who were vaccinated through the SISONKE South African clinical trial of the Ad26.CoV2.S vaccine in healthcare workers (HCWs). PLWH in this group had well-controlled HIV infection. We also enrolled unvaccinated participants previously infected with SARS-CoV-2. Neutralization capacity was assessed by a live virus neutralization assay of the Delta variant. RESULTS: Most Ad26.CoV2.S vaccinated HCWs were previously infected with SARS-CoV-2. In this group, Delta variant neutralization was 9-fold higher compared with the infected-only group and 26-fold higher relative to the vaccinated-only group. No decrease in Delta variant neutralization was observed in PLWH relative to HIV-negative participants. In contrast, SARS-CoV-2-infected, unvaccinated PLWH showed 7-fold lower neutralization and a higher frequency of nonresponders, with the highest frequency of nonresponders in people with HIV viremia. Vaccinated-only participants showed low neutralization capacity. CONCLUSIONS: The neutralization response of the Delta variant following Ad26.CoV2.S vaccination in PLWH with well-controlled HIV was not inferior to HIV-negative participants, irrespective of past SARS-CoV-2 infection. In SARS-CoV-2-infected and nonvaccinated participants, HIV infection reduced the neutralization response to SARS-CoV-2, with the strongest reduction in HIV viremic individuals.

Randomised trials of COVID-19 vaccines in Africa – charting the path forward

Vaccines have played a critical role in controlling disease outbreaks, hence the proliferation of the development and testing of multiple vaccine candidates during the COVID-19 pandemic. Randomised trials are gold standards for evaluating the safety and efficacy of pharmaceutical interventions such as COVID-19 vaccines. However, contextual differences may attenuate effects of COVID-19 vaccines. Thus, the need to conduct COVID-19 vaccine trials in all settings, including in Africa. We conducted a crosssectional analysis of planned, ongoing, and completed COVID-19 vaccine trials in Africa. We searched the South African National Clinical Trials Register, Pan African Clinical Trials Registry, and International Clinical Trials Registry Platform (ICTRP) on 12 January and 30 April 2022: and complemented this with a search of ClinicalTrials.gov on 17 May 2022. We screened the search output and included randomised trials with at least one recruitment site in Africa. We identified only 108 eligible trials: 90 (83%) evaluating candidate COVID-19 vaccines, 11 (10%) assessing if existing vaccines could prevent SARS-CoV-2 infection, and 7 (7%) evaluating interventions for improving COVID-19 vaccination coverage. South Africa had the highest number of trials at 58 (54%). Beyond South Africa, countries with more than 10 trial sites include Kenya, Ghana, Egypt, Uganda, and Zimbabwe. Among the trials, 14 (13%) do not have principal investigators based in Africa, 39 (30%) are funded by industry, and 91 (84%) are funded by institutions based outside the host country. COVID-19 vaccine trials with recruitment sites in Africa represented only 7% of the 1453 COVID-19 vaccine trials in the ICTRP The paucity of COVID-19 vaccine trials conducted on the African continent is a cause for concern. This has implications for the role that Africa may play in future pandemics.

Safety evaluation of the single-dose Ad26.COV2.S vaccine among healthcare workers in the Sisonke study in South Africa: A phase 3b implementation trial.

BACKGROUND: Real-world evaluation of the safety profile of vaccines after licensure is crucial to accurately characterise safety beyond clinical trials, support continued use, and thereby improve public confidence. The Sisonke study aimed to assess the safety and effectiveness of the Janssen Ad26.COV2.S vaccine among healthcare workers (HCWs) in South Africa. Here, we present the safety data. METHODS AND FINDINGS: In this open-label phase 3b implementation study among all eligible HCWs in South Africa registered in the national Electronic Vaccination Data System (EVDS), we monitored adverse events (AEs) at vaccination sites through self-reporting triggered by text messages after vaccination, healthcare provider reports, and active case finding. The frequency and incidence rate of non-serious and serious AEs were evaluated from the day of first vaccination (17 February 2021) until 28 days after the final vaccination in the study (15 June 2021). COVID-19 breakthrough infections, hospitalisations, and deaths were ascertained via linkage of the electronic vaccination register with existing national databases. Among 477,234 participants, 10,279 AEs were reported, of which 138 (1.3%) were serious AEs (SAEs) or AEs of special interest. Women reported more AEs than men (2.3% versus 1.6%). AE reports decreased with increasing age (3.2% for age 18-30 years, 2.1% for age 31-45 years, 1.8% for age 46-55 years, and 1.5% for age > 55 years). Participants with previous COVID-19 infection reported slightly more AEs (2.6% versus 2.1%). The most common reactogenicity events were headache (n = 4,923) and body aches (n = 4,483), followed by injection site pain (n = 2,767) and fever (n = 2,731), and most occurred within 48 hours of vaccination. Two cases of thrombosis with thrombocytopenia syndrome and 4 cases of Guillain-Barré Syndrome were reported post-vaccination. Most SAEs and AEs of special interest (n = 138) occurred at lower than the expected population rates. Vascular (n = 37; 39.1/100,000 person-years) and nervous system disorders (n = 31; 31.7/100,000 person-years), immune system disorders (n = 24; 24.3/100,000 person-years), and infections and infestations (n = 19; 20.1/100,000 person-years) were the most common reported SAE categories. A limitation of the study was the single-arm design, with limited routinely collected morbidity comparator data in the study setting. CONCLUSIONS: We observed similar patterns of AEs as in phase 3 trials. AEs were mostly expected reactogenicity signs and symptoms. Furthermore, most SAEs occurred below expected rates. The single-dose Ad26.COV2.S vaccine demonstrated an acceptable safety profile, supporting the continued use of this vaccine in this setting. TRIAL REGISTRATION: ClinicalTrials.gov NCT04838795; Pan African Clinical Trials Registry PACTR202102855526180.

Impact of Preexisting Anti-Adenovirus 26 Humoral Immunity on Immunogenicity of the Ad26.COV2.S Coronavirus Disease 2019 Vaccine.

This secondary analysis of the phase 3 ENSEMBLE trial (NCT04505722) assessed the impact of preexisting humoral immunity to adenovirus 26 (Ad26) on the immunogenicity of Ad26.COV2.S-elicited severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)-specific antibody levels in 380 participants in Brazil, South Africa, and the United States. Among those vaccinated in Brazil and South Africa, 31% and 66%, respectively, had prevaccination serum-neutralizing activity against Ad26, with little preexisting immunity detected in the United States. Vaccine recipients in each country had similar postvaccination spike (S) protein-binding antibody levels, indicating that baseline immunity to Ad26 has no clear impact on vaccine-induced immune responses.