Individual vaccine efficacy variation with time since mRNA BNT162b2 vaccination estimated by rapid, quantitative antibody measurements from a finger-prick sample.

We show that an individual's immune status to Covid-19 can be monitored through quantitative antibody measurements using a method specifically designed for high throughput and accuracy from a finger-prick blood sample. The quality of the rapid test results is comparable to that from major commercial laboratory testing kits. Anti-Receptor Binding Domain (RBD) IgG concentration showed a log-normal distribution with mean decreasing with time following the second vaccination with mRNA BNT162b2 (Pfizer). Using a model for an individual's antibody concentration-dependent vaccine efficacy allowed comparison with literature data on changing vaccine efficacy against symptomatic disease across a population. In this small trial (n = 100) estimated median vaccine efficacy was 90% (range 65-95%) < 90 days post vaccination, 75% (range 35 - 90%) 90 - 170 days and 65% (range 35-90%) 170 - 230 days. The results provide strong support for personalized booster programmes that, by targeting people in the tail of the distribution, should be more effective at diminishing breakthrough infection and optimising booster dose supply than a program that simply mandates a booster at a specific post-vaccination time point.