Kinetics and persistence of anti-SARS-CoV-2 neutralisation and antibodies after BNT162b2 vaccination in a Swiss cohort.

Introduction: Since the emergence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), substantial effort has been made to gain knowledge about the immunity elicited by infection or vaccination.

Methods: We studied the kinetics of antibodies and virus neutralisation induced by vaccination with BNT162b2 in a Swiss cohort of SARS-CoV-2 naïve (n = 40) and convalescent (n = 9) persons. Blood sera were analysed in a live virus neutralisation assay and specific IgG and IgA levels were measured by enzyme-linked immunoassay and analysed by descriptive statistics.

Results: Virus neutralisation was detected in all individuals 2-4 weeks after the second vaccine. Both neutralisation and antibodies remained positive for >4 months. Neutralisation and antibodies showed positive correlation, but immunoglobulin G (IgG) and immunoglobulin A (IgA) seroconversion took place 2-4 weeks faster than neutralisation. Spike-protein specific IgG levels rose significantly faster and were more stable over time than virus neutralisation titres or IgA responses. For naïve but not convalescent persons, a clear boosting effect was observed. Convalescent individuals showed faster, more robust and longer-lasting immune responses after vaccination compared to noninfected persons. No threshold could be determined for spike protein-specific IgG or IgA that would confer protection in the neutralisation assay, implicating the need for a better correlate of protection then antibody titres alone.

Conclusions: This study clearly shows the complex translation of antibody data and virus neutralisation, while supporting the evidence of a single dose being sufficient for effective antibody response in convalescent individuals.