Dynamics of antibody response to BNT162b2 vaccine after six months: a longitudinal prospective study

Background: SARS-CoV-2 mRNA vaccines have proven high efficacy, however, limited data exists on the duration of immune responses and their relation to age and side effects. Methods: We studied the antibody and memory T cell responses after the two-dose BNT162b2 vaccine in 122 volunteers up to 6 months and correlated the findings with age and side effects. Findings: We found a robust antibody response to Spike protein after the second dose. However, the antibody levels declined at 12 weeks and 6 months post-vaccination, indicating a waning of the immune response over time. At 6 months after the second dose, the Spike antibody levels were similar to the levels in persons vaccinated with one dose or in COVID-19 convalescent individuals. The antibodies efficiently blocked ACE2 receptor binding to SARS-CoV-2 Spike protein of five variants of concern at one week but this was decreased at three months. 87% of individuals developed Spike-specific memory T cell responses, which were lower in individuals with increased proportions of immunosenescent CDS' TEMRA cells. We found antibody response to correlate negatively with age and positively with the total score of vaccination side effects. Interpretation: The mRNA vaccine induces a strong antibody response to SARS-CoV-2 and five VOCs at 1 week post-vaccination that decreases thereafter. T cell responses, although detectable in the majority, were lower in individuals with higher T cell immunosenescence. The deterioration of vaccine response suggests the need to monitor for the potential booster vaccination. (C) 2021 The Authors. Published by Elsevier Ltd.

Automated summary

The study found that antibody levels declined at 12 weeks and 6 months after receiving two doses of BNT162b2 vaccine, with Spike antibody levels at 6 months being similar to those in individuals who received one dose or had recovered from COVID-19. Most individuals developed Spike-specific memory T cell responses, which were lower in those with higher T cell immunosenescence. Antibody response was negatively correlated with age and positively correlated with the total score of vaccination side effects.