The humoral response to COVID-19 vaccinations can predict the booster effect on health care workers—toward personalized vaccinations?

Background Waning immunity after the coronavirus disease 2019 (COVID-19) vaccinations creates the constant need of boosters. Predicting individual responses to booster vaccines can help in its timely administration. We hypothesized that the humoral response to the first two doses of the BNT162b2 vaccine can predict the response to the booster vaccine. Methods A prospective cohort of hospital health care workers (HCW) that received three doses of the BNT162b2 vaccine. Participants completed serological tests at 1 and 6 months after the second vaccine dose and 1 month after the third. We analyzed predictive factors of antibody levels after the booster using multivariate regression analyses. Results From 289 eligible HCW, 89 (31%) completed the follow-up. Mean age was 48 (±10) and 46 (52%) had daily interaction with patients. The mean (±standard deviation) antibody level 1 month after the second vaccine was 223 (±59) AU/ml, and 31 (35%) had a rapid antibody decline (>50%) in 6 months. Low antibody levels 1 month after the second vaccine and a rapid antibody decline were independent predictors of low antibody levels after the booster vaccine. Conclusions The characteristics of the humoral response to COVID-19 vaccinations show promise in predicting the humoral response to the booster vaccines.