The influence of the host cell on standardisation of influenza vaccine potency

Conventional influenza vaccines are standardised using the single-radial-immunodiffusion (SRD) test where reagents are produced from egg-grown viruses. It is important to ensure homology between SRD antigen reagents and test vaccines. There was concern that cell-grown vaccines may differ antigenically from corresponding egg-grown vaccines, which may in turn affect vaccine standardisation. In an examination of five cell-grown vaccines from two companies, only one vaccine was affected by the specificity of the SRD test. Options for standardisation of cell-grown vaccines are considered and recommendations are made for further studies.