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. 2021 May 4;17(5):1396-1402.
doi: 10.1080/21645515.2020.1830685. Epub 2020 Nov 12.

The effect of sex on responses to influenza vaccines

Lucy Denly  1
Affiliations

The effect of sex on responses to influenza vaccines

Lucy Denly. Hum Vaccin Immunother. .

Abstract

The poor uptake and limited effectiveness of seasonal influenza vaccines mean that influenza continues to create a significant burden of disease. It has been hypothesized that sex differences are present in responses to seasonal influenza vaccines, and that these differences may contribute to this poor vaccine success. This has led to the suggestion that vaccines should be tailored to an individual's biological sex. However, studies in this field are often low quality. Comprehensive analysis of the available literature reveals that there is insufficient evidence to support sex differences in vaccine immunogenicity, effectiveness, or efficacy. Nonetheless, differences in vaccine safety are consistently observed, with females reporting adverse events following immunization more frequently than males. Bias introduced by gender differences in passive reporting of adverse effects may underlie this phenomenon. Highly controlled studies are required in future before any conclusions can be made about potential sex differences in response to seasonal influenza vaccines.

Keywords: Seasonal influenza vaccine; sex differences; vaccine effectiveness; vaccine efficacy; vaccine immunogenicity; vaccine safety.

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Figures

Figure 1.
Figure 1.
Antigenic mismatch decreases effectiveness of seasonal influenza vaccines. The prevalent circulating strains are selected 6 months before the beginning of the flu season, to allow adequate time for vaccine production. These strains are grown in eggs. Mutations may occur in the vaccine strains to increase their ability to grow in eggs (egg-adaptation). Mutations may occur in the circulating strains between selection and vaccine administration (genetic drift). Both types of mutations may lead to antigenic mismatch, so vaccinated populations do not have protection against the influenza strains circulating at the time. This leads to low vaccine effectiveness for that season
Figure 2.
Figure 2.
Test-negative design studies. A form of observational study commonly used in effectiveness studies of influenza vaccination to reduce disease misclassification and confounding by health care-seeking behaviors. However, gender differences in health-seeking behavior may introduce selection bias
See this image and copyright information in PMC

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