Assessing commutability of the first WHO International Standard for antiserum to respiratory syncytial virus

The immunogenicity of RSV vaccines under development or recently licensed is often assessed using virus neutralisation assays. Comparison between studies and laboratories is challenging because various formats of virus neutralisation assays are being used. To overcome this issue, the World Health Organisation (WHO) established an International Standard for antiserum to RSV in 2017. In the present study, we assessed the commutability of the standard for eighteen samples from clinical trials of different RSV vaccine candidates and paediatric serum pools. Eight laboratories participated in the study, testing a panel of blinded samples including the international standard, 16/284. The results showed that use of standard 16/284, as well as its potential replacement 16/322, when used to normalise data, decreased between-laboratory variability and led to better agreement between laboratories. We conclude that standard 16/284 and its potential replacement 16/322 are useful tools for harmonising results from neutralisation assays when assessing RSV vaccines in development and its use in future clinical trials is encouraged.