ABSTRACT
BACKGROUNDFollowing the emergence of the Omicron variant of concern, we investigated immunogenicity, efficacy and safety of BNT162b2 or mRNA1273 fourth dose in an open-label, clinical intervention trial. METHODSPrimary end-points were safety and immunogenicity and secondary end-points were vaccine efficacy in preventing SARS-CoV-2 infections and COVID-19 symptomatic disease. The two intervention arms were compared to a matched control group. Eligible participants were healthcare-workers (HCW) vaccinated with three BNT162b2 doses, and whose IgG antibody levels were [≤]700 BAU (40-percentile). IgG and neutralizing titers, direct neutralization of live VOCs, and T-cell activation were assessed. All participants were actively screened for SARS-CoV-2 infections on a weekly basis. RESULTSOf 1050 eligible HCW, 154 and 120 were enrolled to receive BNT162b2 and mRNA1273, respectively, and compared to 426 age-matched controls. Recipients of both vaccine types had a [~]9-10-fold increase in IgG and neutralizing titers within 2 weeks of vaccination and an 8-fold increase in live Omicron VOC neutralization, restoring titers to those measured after the third vaccine dose. Breakthrough infections were common, mostly very mild, yet, with high viral loads. Vaccine efficacy against infection was 30% (95%CI:-9% to 55%) and 11% (95%CI:-43% to +43%) for BNT162b2 and mRNA1273, respectively. Local and systemic adverse reactions were reported in 80% and 40%, respectively. CONCLUSIONSThe fourth COVID-19 mRNA dose restores antibody titers to peak post-third dose titers. Low efficacy in preventing mild or asymptomatic Omicron infections and the infectious potential of breakthrough cases raise the urgency of next generation vaccine development. Trial registration numberclicaltrials.gov: NCT05231005, NCT05230953
ABSTRACT
Using isolates of SARS-CoV-2 WT, Beta, Delta and most importantly Omicron we studied the capability of the BNT162b2 vaccine given in two or three doses to neutralize major SARS-CoV-2 variants of concern (VOC). We demonstrate low neutralization efficiency against delta and wild-type for vaccines with more than 5 months following the second BNT162b2 dose, with no neutralization efficiency against Omicron. We demonstrate the importance of a third dose, by showing a 100-fold increase in neutralization efficiency of Omicron following a third dose, with a 4-fold reduced neutralization compared to that against the Delta VOC. The durability of the effect of the third dose is yet to be determined.
ABSTRACT
In a prospective cohort study involving 12,413 Health Care Workers (HCW), we assessed immunogenicity, vaccine-effectiveness (VE) and safety of the third BNT162b2 vaccine dose. One month after third dose, anti-RBD-IgG were induced 1.7-folds compared to one month after the second. A significant increase in avidity from 61.1% (95%CI:56.1-66.7) to 96.3% (95%CI:94.2-98.5) resulted in a 6.1-folds neutralizing antibodies induction. Linear mixed model demonstrated that the third dose elicited a greater response among HCW[≥]60 or those with [≥]two comorbidities who had a lower response following the second dose. VE of the third dose relative to two doses was 85.6% (95% CI, 79.2-90.1%). No serious adverse effects were reported. These results suggest that the third dose is superior to the second dose in both quantity and quality of IgG-antibodies and safely boosts protection from SARS-CoV-2 infection by generating high avidity antibodies to levels that are not significantly different between healthy and vulnerable populations.
ABSTRACT
Although SARS-CoV-2 infects the upper respiratory tract, we know little about the amount, type, and kinetics of antibodies (Ab) generated at this site in response to intramuscular COVID-19 vaccination, and whether these Ab protect against subsequent "breakthrough" infections. We collected longitudinal serum and saliva samples from participants receiving two doses of mRNA COVID-19 vaccines over a 6-month period and measured the relative level of anti-Spike and anti-Receptor Binding Domain (RBD) Ab. We detected anti-Spike/RBD IgG and IgA and associated secretory component in the saliva of most participants receiving 1 dose of mRNA vaccine. Administration of a second dose of mRNA boosted the IgG but not the IgA response, with only 30% of participants remaining positive for IgA at this timepoint. At 6 months post-dose 2, these participants exhibited greatly diminished anti-Spike/RBD IgG and IgA levels concomitant with a reduction in neutralizing activity in the saliva, although the level of secretory component associated anti-Spike was less susceptible to decay. Examining two prospective cohorts of subjects that were monitored for infections post-vaccination, we found that participants who were subsequently infected with SARS-CoV-2 had lower levels of vaccine-induced serum anti-Spike/RBD IgA at 2-4 weeks post-dose 2 compared to participants who did not experience an infection, whereas IgG levels were comparable between groups. These data emphasize the importance of developing COVID-19 vaccines that elicit a durable IgA response. One-Sentence SummaryOur study delves into whether intra-muscular mRNA vaccination regimes confer a local IgA response in the oral cavity and whether the IgA response is associated with protection against breakthrough infection.
