A study supported by the National Institutes of Health and performed by investigators from Johns Hopkins shows that reproductive hormones may influence immune response to influenza vaccination. Published in npj Vaccines, the analysis also found evidence that the association may be causal.
For the research, the authors evaluated cytokine and antibody responses to the 2009 H1N1 influenza vaccine in 145 men and women, half of whom were aged 18 to 45 and the other 65 and older. The women of reproductive age had higher concentrations of IL-6 after vaccination than either the men in the younger group or the older women (P= 0.06, one-way ANOVA). The greatest differences were between the younger and older women. The authors noted that IL-6 is crucial for germinal center formation, antibody production, and class switching.
The researchers then conducted a similar experiment in a mouse model, with gonadectomization and replacement of estradiol in the female animals and testosterone in the males before vaccination. They found that the estradiol increased vaccine-induced antibody responses in the female mice whereas testosterone decreased those responses in the male animals.
“What we show here is that the decline in estrogen that occurs with menopause impacts women’s immunity,” said lead investigator Sabra Klein, PhD, in a press release from Johns Hopkins. “Until now, this hasn’t been considered in the context of a vaccine. These findings suggest that for vaccines, one size doesn’t fit all—perhaps men should get larger doses, for example.”
In the report, the authors concluded that their data, “suggest that experimental design and data analyses should consider sex/gender and age in preclinical animal studies as well as in randomized controlled trials of influenza vaccines.”