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.

BACKGROUND: Inactivated whole-virus vaccination elicits immune responses to both SARS-CoV-2 nucleocapsid (N) and spike (S) proteins, like natural infections. A heterologous Ad26.COV2.S booster given at two different intervals after primary BBIBP-CorV vaccination was safe and immunogenic at days 28 and 84, with higher immune responses observed after the longer pre-boost interval. We describe booster-specific and hybrid immune responses over 1 year.
METHODS: This open-label phase 1/2 study was conducted in healthy Thai adults aged ≥ 18 years who had completed primary BBIBP-CorV primary vaccination between 90-240 (Arm A1; n = 361) or 45-75 days (Arm A2; n = 104) before enrolment. All received an Ad26.COV2.S booster. We measured anti-S and anti-N IgG antibodies by Elecsys®, neutralizing antibodies by SARS-CoV-2 pseudovirus neutralization assay, and T-cell responses by quantitative interferon (IFN)-γ release assay. Immune responses were evaluated in the baseline-seronegative population (pre-booster anti-N < 1.4 U/mL; n = 241) that included the booster-effect subgroup (anti-N < 1.4 U/mL at each visit) and the hybrid-immunity subgroup (anti-N ≥ 1.4 U/mL and/or SARS-CoV-2 infection, irrespective of receiving non-study COVID-19 boosters).
RESULTS: In Arm A1 of the booster-effect subgroup, anti-S GMCs were 131-fold higher than baseline at day 336; neutralizing responses against ancestral SARS-CoV-2 were 5-fold higher than baseline at day 168; 4-fold against Omicron BA.2 at day 84. IFN-γ remained approximately 4-fold higher than baseline at days 168 and 336 in 18-59-year-olds. Booster-specific responses trended lower in Arm A2. In the hybrid-immunity subgroup at day 336, anti-S GMCs in A1 were 517-fold higher than baseline; neutralizing responses against ancestral SARS-CoV-2 and Omicron BA.2 were 28- and 31-fold higher, respectively, and IFN-γ was approximately 14-fold higher in 18-59-year-olds at day 336. Durable immune responses trended lower in ≥ 60-year-olds.
CONCLUSIONS: A heterologous Ad26.COV2.S booster after primary BBIBP-CorV vaccination induced booster-specific immune responses detectable up to 1 year that were higher in participants with hybrid immunity.
BACKGROUND: NCT05109559.

BACKGROUND: A single dose of Ad26.COV2.S is well-tolerated and effective in preventing moderate-to-severe disease outcomes due to COVID-19. We evaluated the impact of dose level, number of doses, and dose interval on immunogenicity, reactogenicity, and safety of Ad26.COV2.S in adults. Anamnestic responses were also explored.
METHODS: This randomised, double-blind, placebo-controlled, Phase 2a study was conducted in adults aged 18-55 years and ≥ 65 years (NCT04535453). Four dose levels (1.25 × 1010, 2.5 × 1010, 5 × 1010, and 1 × 1011 viral particles [vp], single and 2-dose schedules, and dose intervals of 56 and 84 days, were assessed. Four or 6 months post-primary vaccination, Ad26.COV2.S 1.25 × 1010 vp was given to evaluate anamnestic responses. Humoral and cell-mediated immune responses were measured. Reactogenicity and safety were assessed in all participants.
RESULTS: All Ad26.COV2.S schedules induced humoral responses with evidence of a dose response relationship. A single dose of Ad26.COV2.S (5 × 1010 vp) induced antibody and cellular immune responses that persisted for up to at least 6 months. In the 2-dose regimens, antibody responses were higher than 1-dose regimens at comparable dose levels, and the magnitude of the immune response increased when the interval between doses was increased (84 days vs 56 days). Rapid, marked immune responses were observed in all groups after vaccine antigen exposure indicating immune memory. Durable immune responses were observed in all groups for up to at least 6 months post-antigen exposure. Strong and consistent correlations between neutralising and binding antibodies were observed CD4 + and CD8 + T cell responses were similar after all regimens. Reactogenicity within 7 days post-vaccination tended to be dose-related.
CONCLUSIONS: The study supports the primary, single dose schedule with Ad26.COV2.S at 5 × 1010 vp and homologous booster vaccination after a 6 month interval. Rapid and marked responses to vaccine antigen exposure indicate induction of immune memory by 1- and 2-dose primary vaccination.

BACKGROUND: Although previous studies found no-increased mortality risk after COVID-19 vaccination, residual confounding bias might have impacted the findings. Using a modified self-controlled case series (SCCS) design, we assessed the risk of non-COVID-19 mortality, all-cause mortality, and four cardiac-related death outcomes after primary series COVID-19 vaccination.
METHODS: We analyzed all deaths between December 14, 2020, and August 11, 2021, among individuals from eight Vaccine Safety Datalink sites. Demographic characteristics of deaths in recipients of COVID-19 vaccines and unvaccinated individuals were reported. We conducted SCCS analyses by vaccine type and death outcomes and reported relative incidences (RI). The observation period for death spanned from the dates of emergency use authorization to the end of the study period (August 11, 2021) without censoring the observation period upon death. We pre-specified a primary risk interval of 28-day and a secondary risk interval of 14-day after each vaccination dose. Adjusting for seasonality in mortality analyses is crucial because death rates vary over time. Deaths among unvaccinated individuals were included in SCCS analyses to account for seasonality by incorporating calendar month in the models.
RESULTS: For Pfizer-BioNTech (BNT162b2), RIs of non-COVID-19 mortality, all-cause mortality, and four cardiac-related death outcomes were below 1 and 95 % confidence intervals (CIs) excluded 1 across both doses and both risk intervals. For Moderna (mRNA-1273), RI point estimates of all outcomes were below 1, although the 95 % CIs of two RI estimates included 1: cardiac-related (RI = 0.78, 95 % CI, 0.58-1.04) and non-COVID-19 cardiac-related mortality (RI = 0.80, 95 % CI, 0.60-1.08) 14 days after the second dose in individuals without pre-existing cancer and heart disease. For Janssen (Ad26.COV2.S), RIs of four cardiac-related death outcomes ranged from 0.94 to 0.98 for the 14-day risk interval, and 0.68 to 0.72 for the 28-day risk interval and 95 % CIs included 1.
CONCLUSIONS: Using a modified SCCS design and adjusting for temporal trends, no-increased risk was found for non-COVID-19 mortality, all-cause mortality, and four cardiac-related death outcomes among recipients of the three COVID-19 vaccines used in the US.

The Sisonke 2 study provided a homologous boost at least 6 months after administration of the priming dose of Ad26.COV2.S for healthcare workers enrolled on the Sisonke phase 3b implementation study. Safety monitoring was via five reporting sources: (i.) self-report through a web-link; (ii.) paper-based case report forms; (iii.) a toll-free telephonic reporting line; (iv.) healthcare professionals-initiated reports; and (v.) active linkage with National Disease Databases. A total of 2350 adverse events were reported by 2117 of the 240 888 (0.88%) participants enrolled; 1625 of the 2350 reported events are reactogenicity events and 28 adverse events met seriousness criteria. No cases of thrombosis with thrombocytopaenia syndrome were reported; all adverse events including thromboembolic disorders occurred at a rate below the expected population rates apart from one case of Guillain Barre Syndrome and one case of portal vein thrombosis. The Sisonke 2 study demonstrates that two doses of Ad26.COV2.S is safe and well tolerated; and provides a feasible model for national pharmacovigilance strategies for low- and middle-income settings.

BACKGROUND: Recently published studies have reported association of COVID-19 vaccine ChAdOx1-S (Vaxzevria) with Guillain Barré Syndrome (GBS). Less is known about the safety of other COVID-19 vaccines with respect to GBS outcome. This study investigated the association of COVID-19 vaccines with GBS in more than 15 million persons aged ≥12 years in Italy.
METHODS: Study population was all individuals aged ≥12 years who received at least one dose of COVID-19 vaccines, admitted to emergency care/hospital for GBS from 27 December 2020-30 September 2021 in Italy. Identification of GBS cases and receipt of at least one dose of mRNA-1273 (Elasomeran), BNT162b2 (Tozinameran), ChAdOx1-S (Vaxzevria) and Ad26.COV2.S (Janssen) through record linkage between regional health care and vaccination registries. Relative Incidence (RI) was estimated Self-controlled case series method adapted to event-dependent exposure using in the 42-day exposure risk period after each dose compared with other observation periods.
RESULTS: Increased risk of GBS was found after first (RI = 6.83; 95% CI 2.14-21.85) and second dose (RI = 7.41; 2.35-23.38) of mRNA-1273 and first dose of ChAdOx1-S (RI = 6.52; 2.88-14.77). Analysis by age found an increased risk among those aged≥60 years after first (RI = 8.03; 2.08-31.03) and second dose (RI = 7.71; 2.38-24.97) of mRNA-1273. The first dose of ChAdOx1-S was associated with GBS in those aged 40-59 (RI = 4.50; 1.37-14.79) and in those aged ≥ 60 years (RI = 6.84; 2.56-18.28).
CONCLUSIONS: mRNA-1273 and ChAdOx1-S vaccines were associated with an increased risk of GBS however this risk resulted in a small number of excess cases. Limitations were loss of GBS outpatient cases and imprecision of the estimates in the subgroup analysis due to a low number of events.

OBJECTIVE: Guillain-Barré syndrome (GBS) has been inconsistently associated with some coronavirus disease 2019 (COVID-19) vaccines. We aimed to quantify the risk of GBS according to the type of COVID-19 vaccine in a large population.
METHODS: Using the French National Health Data System linked to the COVID-19 vaccine database, we analyzed all individuals aged 12 years or older admitted for GBS from December 27, 2020, to May 20, 2022. We estimated the relative incidence (RI) of GBS within 1-42 days after vaccination up to the first booster dose compared with baseline periods using a self-controlled case series design. We then derived the number of cases attributable to the vaccination. Analyses were adjusted for the period and stratified by age group, sex, and for the presence of severe acute respiratory syndrome coronavirus 2 or common acute infections.
RESULTS: Of 58,530,770 people aged 12 years or older, 88.8% received at least 1 COVID-19 vaccine dose and 2,229 were hospitalized for GBS during the study period. Patients had a median age of 57 years, and 60% were male patients. The RI of GBS between 1-42 days was 2.5 (95% CI 1.8-3.6) for the first dose of ChAdOx1-S and 2.4 (95% CI 1.2-5.0) for the unique dose of Ad26.COV2.S vaccine. We estimated 6.5 attributable GBS cases per million persons having received a first dose of ChAdOx1-S and 5.7 cases per million for the Ad26.COV2.S vaccine. Except for the age group of 12-49 years after the second dose of the messenger RNA (mRNA)-1273 vaccine (RI 2.6, 95% CI 1.2-5.5), none of the RI estimates were found significantly increased for the mRNA vaccines.
CONCLUSIONS: In summary, we found increased risks of GBS after the first administration of ChAdOx1-S and Ad26.COV2.S vaccines. In this comprehensive assessment at the French population level, there was no statistically significant increase in the risk of GBS after the administration of mRNA vaccines. This is reassuring in the context of the ongoing and future use of mRNA-based booster vaccination.

We carried out a study to estimate the vaccine effectiveness (VE) of homologous vaccination schedules against COVID-19, using data from mandatory information systems from Bogota, Colombia.
A test-negative case-control study in adults from Bogota (Colombia), between March 1st of 2021 and February 25th of 2022. We assess VE among symptomatic COVID-19 cases during the Mul, Delta, and Omicron predominance periods in Bogota, with controls matched by sex, age (±5 years), and date of testing (±7 days), using a case:control ratio of 1:1. We selected homologous vaccination schedules with ChAdOx1, CoronaVac, BNT162b2, mRNA-1273, and Ad26.COV2.S. VE was reported as one minus the odds ratio in adjusted conditional logistic regressions, with their 95% confidence intervals (CI). A p-value < 0.05 was considered statistically significant.
52,913 cases were matched to controls, 16,722 for Mu, 14,094 for Delta, and 22,097 for Omicron. VE was high against COVID-19 during Mu weeks with full vaccination using the monovalent BNT162b2 (VE: 69; 95% CI, 65 to 72) vaccine and ChAdOx1 (VE: 64; 95% CI, 31 to 81) and significantly lower with CoronaVac (P < 0.001) and Ad26.COV2.S (P = 0.005). During Delta, VE against COVID-19 was higher with BNT162b2 (VE: 55; 95% CI, 51 to 58). The VE for COVID-19 cases during Omicron was higher with a booster dose of monovalent BNT162b2 (VE: 45; 95% CI, 34 to 54). The VE of primary series and booster for ChAdOx1, Ad26.COV2.S, and CoronaVac did not show protection for Omicron.
Our study provides further evidence on the protective effect of mRNA vaccines for Omicron, and warrant that the duration of protection against symptomatic infection may last for only a few months.

To combat the SARS-CoV-2 pandemic, multiple vaccines using different manufacturing platforms have been developed, including NVX-CoV2373 (an adjuvanted recombinant protein vaccine). As SARS-CoV-2 variants have emerged, some of which evade vaccine-induced immunity, introduction of vaccine booster doses has become critical. Employing different vaccine types for primary series vaccination and boosting could expand vaccine coverage and access. This study assessed whether NVX-CoV2373 would induce robust responses when used as a booster.
The 2019nCoV-307 study was a phase 3, randomized, observer-blinded trial evaluating immunogenicity and safety of NVX-CoV2373 in previously vaccinated adults aged 18-49 years in the United States (NCT05463068). Participants were randomized 1:1:1 to receive one intramuscular injection of NVX-CoV2373 from one of three different manufacturing lots. Immunogenicity was assessed by immunoglobulin G (IgG) and neutralizing antibodies (NAb). These responses were compared for the three lots, and for participants with primary series with or without a prior booster dose of the mRNA-1273, BNT162b2, Ad26.COV2.S, or NVX-CoV2373 COVID-19 vaccines.
A total of 911 participants were randomized between July 11 and 13, 2022, with 905 being assessed for safety and 848 for immunogenicity. Immunogenicity of NVX-CoV2373 met prespecified equivalence criteria between lots, and the booster dose was well-tolerated. NVX-CoV2373 induced robust IgG and NAb responses when used as a first or later booster dose, regardless of primary series vaccine type. Seroconversion rates were also similar across previous vaccine types. Induced antibodies were strongly reactive, even to the immune-evasive Omicron BA.1 and BA.5 variants.
NVX-CoV2373 showed consistent immunogenicity between lots, with no new safety signals identified. Use of NVX-CoV2373 as a booster dose (first or later) is supported.

Thrombosis with thrombocytopenia syndrome (TTS) is a very rare disorder described after vaccination with adenoviral vector-based COVID-19 vaccines. Co-occurring thrombosis with thrombocytopenia reported after vaccination can be a proxy for identification of TTS.
Descriptive database review of all cases of co-occurring (within 42 days) thrombosis with thrombocytopenia in participants in Ad26.COV2.S clinical trials or recipients of Ad26.COV2.S in real-world clinical practice. Cases were retrieved from Janssens\' clinical trial and Global Medical Safety databases.
There were 34 cases of co-occurring thrombosis with thrombocytopenia in Ad26.COV2.S recipients (46 per 100,000 person-years) and 15 after placebo (75 per 100,000 person-years) in clinical trials. Among Ad26.COV2.S recipients, mean age at the time of the event was 63 years (range 25-85), 82 % were male, mean time-to-onset 112 days (range 8-339) post-last Ad26.COV2.S dose, 26 events occurred post-dose-1, and 7 within a 28-day risk window post-vaccination. Diagnostic certainty was evaluated using Brighton Collaboration, US Centers for Disease Control and Prevention, and European Medicines Agency Pharmacovigilance Risk Assessment Committee case definitions. One case met the highest level of diagnostic certainty for all 3 definitions. There were 355 spontaneous reports of co-occurring thrombosis with thrombocytopenia in the Global Medical Safety database, 47 % males, 85 % within 28-days after vaccination. Twenty-seven cases met the highest level of diagnostic certainty for all definitions, 21 female, 19 with cerebral venous sinus thrombosis, age-range 18-68 years. Time-to-onset was 7-14 days post-vaccination in 20 cases. There were 8 fatalities.
TTS induced by Ad26.COV2.S is very rare. Most co-occurring thrombosis with thrombocytopenia does not constitute TTS.