New Study Suggests Possible Increased Risk of Spontaneous Abortion Following Influenza Vaccine Early in Pregnancy
A large body of evidence demonstrates the safety of IIV for both pregnant women and their unborn children.[1-5] Pregnant women who receive influenza vaccine have a lower likelihood of stillbirth than those who do not.
Donahue et al. recently reported results from a case-control study examining the risk of spontaneous abortion (SAb) following receipt of inactivated influenza vaccines containing H1N1pdm09 in the 2010-11 and 2011-12 flu seasons. The study found as association between influenza vaccine and SAb, particularly among women who had also been vaccinated in the previous year. The Donahue et al. findings need to be interpreted in the context of other epidemiological data.
Five observational studies examining associations between SAb and receipt of inactivated influenza vaccine in the first trimester did not find an association.[1-5] However, none of these studies examined the effect of multiple dosing.
Concomitant administration of Tdap and influenza vaccines during pregnancy is not associated with a higher risk of adverse outcomes compared to sequential vaccination.
1. Chambers CD, et al. Safety of the 2010–11, 2011–12, 2012–13, and 2013–14 seasonal influenza vaccines in pregnancy: Birth defects, spontaneous abortion, preterm delivery, and small for gestational age infants, a study from the cohort arm of VAMPSS. Vaccine 2016;34(37): 4443-9. Link to abstract
2. Chavant F, et al. The PREGVAXGRIP Study: a Cohort Study to Assess Foetal and Neonatal Consequences of In Utero Exposure to Vaccination Against A(H1N1)v2009 Influenza. Drug Safety 2013;36(6):455-65. Link to abstract
3. Oppermann M, et al. A(H1N1)v2009: A controlled observational prospective cohort study on vaccine safety in pregnancy. Vaccine 2012;30(30):4445-52. Link to abstract
4. Pasternak B, et al. Vaccination against pandemic A/H1N1 2009 influenza in pregnancy and risk of fetal death: cohort study in Denmark. BMJ 2012;344:e2794. Link to abstract
5. Tavares F, et al. Pregnancy and safety outcomes in women vaccinated with an AS03-adjuvanted split virion H1N1 (2009) pandemic influenza vaccine during pregnancy: A prospective cohort study. Vaccine 2011;29(37):6358-65. Link to abstract
6. Bratton KN, et al. Maternal influenza immunization and birth outcomes of stillbirth and spontaneous abortion: a systematic review and meta-analysis. Clinical infectious diseases: an official publication of the Infectious Diseases Society of America 2015;60:e11-9. Link to abstract