Immune Response to Flu Increases During Pregnancy

During pregnancy, women have an increased immune response to influenza, which may explain why infected pregnant women have increased rates of morbidity and mortality, the results of a recent study suggest.

The study, published online on September 22, 2014, in the Proceedings of the National Academy of Sciences, examined natural killer (NK)-and T-cell responses to influenza during pregnancy. Immune responses were measured for pregnant women and nonpregnant controls immediately before and 7 days after they received an inactivated influenza vaccination, and 6 weeks after the women gave birth.

The results indicated that pregnant women had a significantly increased percentage of NK cells producing a response to the pH1N1 virus than nonpregnant women both before and after vaccination. Pregnant women also had significantly increased T-cell responses to the pH1N1 and the H3N2 strains.

The results of the study were surprising because previous research has shown that the overall production of both NK and T cells is suppressed during pregnancy.

“Robust cellular immune responses to influenza during pregnancy could drive pulmonary inflammation, explaining increased morbidity and mortality,” the study authors explained.