Impact of SARS-CoV-2 infection on vaccine-induced immune responses over time.

Objective: To determine the long-term impact of prior SARS-CoV-2 infection on immune responses after COVID-19 vaccination. Methods: Using longitudinally collected blood samples from the COMMUNITY study, we determined binding (WHO BAU mL-1) and neutralising antibody titres against ten SARS-CoV-2 variants over 7 months following BNT162b2 in SARS-CoV-2-recovered (n = 118) and SARS-CoV-2-naïve (n = 289) healthcare workers with confirmed prior SARS-CoV-2 infection. A smaller group with (n = 47) and without (n = 60) confirmed prior SARS-CoV-2 infection receiving ChAdOx1 nCoV-19 was followed for 3 months. SARS-CoV-2-specific memory T-cell responses were investigated in a subset of SARS-CoV-2-naïve and SARS-CoV-2-recovered vaccinees. Results: Vaccination with both vaccine platforms resulted in substantially enhanced T-cell responses, anti-spike IgG responses and neutralising antibodies effective against ten SARS-CoV-2 variants in SARS-CoV-2-recovered participants as compared to SARS-CoV-2-naïve participants. The enhanced immune responses sustained over 7 months following vaccination. Conclusion: These findings imply that prior SARS-CoV-2 infection should be taken into consideration when planning booster doses and design of current and future COVID-19 vaccine programmes.