USE OF SEASONAL INFLUENZA VACCINES IN PREGNANCY

Seasonal influenza vaccines are inactivated trivalent or quadrivalent vaccines produced in anticipation of the expected circulating strains of seasonal influenza virus for the coming influenza season.

Data on seasonal and pandemic influenza infection suggest that pregnant women, especially those with pre-existing medical conditions and in the later stages of pregnancy, are at increased risk of influenza complications and are more likely to experience adverse fetal outcomes such as miscarriage or stillbirth. Data regarding the risk of congenital malformation following maternal influenza infection during pregnancy are conflicting. Some studies have reported an association, but a causal link to maternal fever rather than a direct effect of the influenza virus on the fetus has been proposed.

Because the seasonal influenza vaccine antigen formulation changes each year, the currently available data on exposure in pregnancy relate to various formulations of influenza vaccines. Overall, there is no indication that exposure to inactivated influenza vaccines in pregnancy is associated with an increased risk of adverse fetal effects. Additionally, there is evidence that seasonal influenza vaccination during pregnancy confers immunity to influenza in the neonate.

Public Health England recommends that all pregnant women, regardless of stage of pregnancy, should receive the seasonal influenza vaccine given the increased risk of morbidity and mortality associated with influenza infection during pregnancy. 

Although there are no known adverse fetal effects of maternal influenza vaccination in pregnancy, other risk factors may be present in individual cases which may independently increase the risk of adverse pregnancy outcome. Clinicians are reminded of the importance of consideration of such factors when performing case-specific risk assessments.