Relating in vitro neutralisation level and protection in the CVnCoV (CUREVAC) trial

A recent study analysed the relationship between neutralising antibody response and protection from SARS-CoV-2 infection across eight vaccine platforms ¹ . The efficacy results from a phase 2b/3 trial of a ninth vaccine candidate, CVnCoV (CUREVAC), was announced on 16 June 2021 ² . The low efficacy of this new mRNA vaccine, which showed only 47% protection from symptomatic SARS-CoV-2 infection, was surprising given the high efficacy of two previous mRNA-based vaccines ^3,4 . A number of factors have been suggested to play a role in the low efficacy in the CVnCoV study, particularly around the dose and immunogenicity of the vaccine (which uses an unmodified mRNA construct ^5,6 ) and the potential role of infection with SARS-CoV-2 variants (which were the dominant strains observed in the CVnCoV trial) ² .