Reply letter to “Vaccine effectiveness of recombinant and standard dose influenza vaccines against outpatient illness during 2018–2019 and 2019–2020 calculated using a retrospective test-negative design”

Abstract

A recent study by Zimmerman et al. (2023) reported non-significant higher relative vaccine effectiveness of recombinant (RIV4) over the standard-dose influenza vaccines (SDIV) against outpatient illness during the 2018–19 and 2019–20 vaccination seasons. We agree with the authors’ conclusions and would like to emphasize minimal difference between RIV4 and SDIV using Number Needed to Vaccinate (NNV). The NNV analysis showed 8.9 for the RIV4 and 10 for the SDIV in the 50–64 age group. In the 65+ age group, the NNV was 10.6 for the RIV4 and 11.4 for the SDIV. This indicates a minimal difference between both vaccines and hence they both can be used in immunization programs to improve vaccine coverage.

Keywords

• number needed to vaccinate
• standard-dose quadrivalent vaccine
• recombinant quadrivalent vaccine
• vaccine shortage
• vaccine coverage
• influenza vaccine
• flu