Age-Related Dynamics of Serum Anti-Spike IgG Ab After the Third Dose of BNT162b2 Vaccine in a Naive Health Care Workers Population

The kinetics of postvaccination serum anti-Spike IgG concentration were determined in 1,541 health care workers (Sant'Andrea Hospital of Rome, Italy) with no prior infection by SARS-COV-2. Anti-Spike IgG were measured at 3, 12, and 24 weeks after the completion of the primary vaccine cycle (two doses of the BNT162b2 vaccine by Biontech/Pfizer) and 3 weeks apart a third BNT162b2 dose. Stratification of the study population by age (decades from 21-30 to 61-70) highlighted that 24 weeks after cycle completion all age groups had an order of magnitude reduction in serum IgG titers. Considering older adults (age 61-70), they had significantly lower serum IgG titers at each time point compared with younger people, except after the booster dose, which induced similar and elevated IgG titers despite the age.