Antibody response to first and second dose of BNT162b2 in a cohort of characterized healthcare workers

Background: Vaccine-induced population immunity is a key global strategy to control coronavirus disease 2019 (COVID-19). The rapid implementation and availability of several COVID-19 vaccines is now a global health-care priority but more information about humoral responses to single- and double-dose vaccine is needed. Methods: 163 health care workers (HCW) of the Padua University Hospitals, who underwent a complete vaccination campaign with BNT162b2 vaccine were asked to collect serum samples at 12 (t12) and 28 (t28) days after the first inoculum to allow the measurement of SARS-CoV-2 Antibodies (Ab) using chemiluminescent assays against the spike (S) protein and the Receptor Binding Domain (RBD) of the virus, respectively. Results: Significant differences were found at t12 for infection-naive and subjects with previous-natural infection who present higher values of specific antibodies, while no significant differences have been found between t12 and t28. No statistically significant difference was found between male and female, while lower Ab levels have been observed in subjects older than 60 years at t12 but not at t28. Conclusions: Our study confirms observed differences in vaccine responses between infection-naive and subjects with previous natural infection at t12 but not for a longer time. The influence of sex and age deserves further studies, even if the relationship with age seems particularly significant.

Automated summary

The study found significant differences in antibody levels at day 12 after receiving the BNT162b2 vaccine between infection-naive individuals and those with previous natural infection, but no differences were observed thereafter. There were no statistically significant differences between males and females, while individuals over 60 years of age had lower antibody levels at day 12 but not at day 28. The influence of sex and age on vaccine responses warrants further investigation, with age showing particular significance.