Flu vaccine accepted by pregnant women, not linked to miscarriage

BOSTON — Pregnant women were more likely to receive the influenza vaccine when compared with years prior. Those who received the vaccine were no more likely to have a miscarriage when compared with those who did not receive the vaccine, according to new findings from two studies presented here.

“Pregnant women are understandably concerned about protecting their unborn babies, which makes it all the more important for them to understand that getting a flu shot during pregnancy is an important way to protect the baby, as well as themselves,” Kathleen Neuzil, MD, a member of IDSA’s Pandemic Influenza Task Force and clinical professor in the School of Medicine at the University of Washington, said in a press release.

Increased vaccination rates

Marci Drees, MD, of Christiana Care Health Services in Delaware, and colleagues surveyed postpartum women during the 2009 to 2010 and 2010 to 2011 influenza seasons to compare vaccine uptake and reasons for lack of vaccination.

During the 2009 to 2010 H1N1 season, 61% of postpartum women reported receiving the seasonal influenza vaccine during pregnancy vs. 55% during the 2010 to 2011 season. Of those who declined the vaccine, concern about safety was a primary barrier for 66% of women during 2009 to 2010 vs. only 26% of those who cited safety concerns during 2010 to 2011.

Common reasons for refusing vaccination included: not usually getting the flu vaccine (62%); lack of perceived risk for influenza (50%); and lack of perceived risk for severe illness from influenza (35%).

“So far, all efforts to increase pregnant women’s flu vaccination rates have been sustained past the immediate urgency of the 2009 H1N1 pandemic,” Drees told Infectious Disease News. “While safety is always a critical element of education targeted to pregnant women, in our study, they had many of the common concerns that non-pregnant people do. If we want to continue to sustain or improve flu vaccination rates in this population, continued vigilance and continued efforts will be needed.”

Flu vaccine not linked to miscarriage

In a retrospective, case-control study, Stephanie Irving, MHS, epidemiologist at the Marshfield Clinic Research Foundation in Wisconsin, and colleagues assessed the association between early pregnancy loss that occurred before the first 20 weeks of gestation and the receipt of influenza vaccine during the previous 4 weeks.

Stephanie Irving, MHS

Confirmed cases of early pregnancy loss among women aged 18 to 44 years during the fall of 2005 or 2006 were matched 1:1 to women who had a live birth or stillbirth that occurred after 20 weeks (controls).

Of the 243 matched pairs, the researchers observed no association between early pregnancy loss and influenza vaccination (adjusted OR=1.2; 95% CI, 0.5-2.7).

Compared with 16% of cases, 13% of controls received the vaccine before the matched-date of early pregnancy loss. Further, 7% of cases and 6% of controls were vaccinated within the 28 day risk-window before the fetal demise of the matched pair, according to the researchers.

“Influenza vaccination is currently recommended during all trimesters of pregnancy, but some providers and women remain hesitant to vaccinate in early pregnancy,” Irving told Infectious Disease News. “These findings should reassure individuals who are concerned about this specific outcome.”– by Ashley DeNyse

For more information:

Drees M. #540. Presented at: IDSA 49th Annual Meeting; Oct. 20-23, 2011; Boston.
Irving S. #535. Presented at: IDSA 49th Annual Meeting; Oct. 20-23, 2011; Boston.

Disclosure: The researchers report no relevant financial disclosures.

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Flu vaccine accepted by pregnant women, not linked to miscarriage