Background: RNA vaccines against Covid-19 have demonstrated ∼95% efficacy in Phase III clinical trials. Although complete vaccination consisted of two-doses, the onset of protection for both licensed RNA vaccines was observed as early as 12 days after a single dose. The adaptive immune response that coincides with this onset of protection could represent the necessary elements of immunity against Covid-19.
Methods: Serological and T cell analysis was performed in a cohort of 20 healthcare workers after receiving the first dose of Pfizer/BioNTech BNT162b2 vaccine. The primary endpoint was the adaptive immune responses detectable at Days 7 and 10 after dosing.
Results: Spike-specific T cells and binding antibodies were detectable 10 days after the first dose of vaccine, in contrast to receptor-blocking and SARS-CoV-2 neutralising antibodies which were mostly undetectable at this early time-point.
Conclusions: Our findings suggest that early T cell and binding antibody responses, rather than either receptor-blocking or virus neutralizing activity, induced early protection against Covid-19.
Funding: The study was funded by a generous donation from The Hour Glass to support Covid-19 research.
Keywords: COVID-19; RNA vaccine; T cells; binding antibodies; neutralizing antibodies; vaccine efficacy.
© 2021 The Author(s).