ABSTRACT
A third mRNA-based "booster" vaccination is the favored strategy to maintain protection against SARS-CoV-2 infection. Yet, significant waning of specific immunity within six months after 2nd vaccination, along with higher incidence of breakthrough infections associated with the time elapsed since 2nd vaccination raises concerns regarding the durability of immunity also after 3rd vaccination. We assessed virus-specific serum antibody and T cell response in the blood after vaccination with the mRNA vaccine BNT162b2 in more than 50 individuals older than 80 years. All old adults demonstrated a strong humoral response to 3rd vaccination which was at average higher and waned slower than the response to 2nd vaccination, indicative of enhanced humoral immunity. In contrast, their respective T cell response quantitatively limited to the level obtained after 2nd vaccination, with similar waning over time and no evidence for enhanced IFNg production. Because BNT162b2-mediated protection from the Omicron variant relies more on T cells than antibodies, our findings raise concern on the durability of protection from the Omicron variant by BNT162b2 in the senior population.
