Prediction of long-term kinetics of vaccine-elicited neutralizing antibody and time-varying vaccine-specific efficacy against the SARS-CoV-2 Delta variant by clinical endpoint

Abstract

Evidence on vaccine-specific protection over time and boosting impact against the Delta variant across different clinical endpoints and age groups is urgently needed. To address this, we used a previously published model, combined with neutralization data for four vaccines - mRNA-1273, BNT162b2, NVX-CoV2373, and CoronaVac - to evaluate long-term dynamics of neutralizing antibody and to predict time-varying efficacy against the Delta variant by specific vaccine, age group, and clinical severity. We found that booster vaccination produces higher neutralization titers compared with titers observed following primary-series vaccination for all vaccines studied. We estimate the efficacies of mRNA-1273 and BNT162b2 against Delta variant infection to be 63.5% (95%CI: 51.4-67.3%) and 78.4% (95%CI: 72.2-83.5%), respectively, 14-30 days after the second dose, and that efficacies decreased to 36.0% (95%CI: 24.1-58.0%) and 38.5% (95%CI: 28.7-49.1%) 6-8 months later. After administration of booster doses, efficacies against the Delta variant would be 97.0% (95%CI: 96.4-98.5%) and 97.2% (95.7-98.1%). All four vaccines are predicted to provide good protection against severe illness from the Delta variant after both primary and booster vaccination. Long-term monitoring and surveillance of antibody dynamics and vaccine protection, as well as further validation of neutralizing antibody or other markers that can serve as correlates of protection against SARS-CoV-2 and its variants are needed to inform COVID-19 pandemic preparedness.