17β-Estradiol restores antibody responses to an influenza vaccine in a postmenopausal mouse model

Post-menopausal women belong to an age group that is highly susceptible to influenza infection and its most serious complications. However, data on the immunogenicity of influenza vaccines in these women is limited. Therefore, the antibody response to influenza vaccination was assessed in a postmenopausal mouse model. An inactivated-detergent-split vaccine from the A/New Caledonia/20/99 (H1N1) influenza virus strain was given to three groups of mice: ovariectomized (OVEX), OVEX with 17β-estradiol replacement (OVEX+E2), and sham-OVEX. The OVEX+E2 group produced influenza virus-specific serum antibodies, including neutralizing antibodies, at significantly higher levels (p<0.001) than did OVEX mice. These levels matched those observed in the sham-OVEX group, indicating that ovariectomy negatively modulates the antibody response to the influenza vaccine, whereas 17β-estradiol replacement restores this response to levels observed in intact animals. Our findings suggest that immunogenicity and efficacy of influenza vaccines need to be evaluated in postmenopausal women, including women receiving hormone replacement therapy.