H1N1 Flu Vaccine Safe for Expectant Moms, Offspring: Study

Second study reports slight increase in Guillain-Barre syndrome after vaccination

By Serena Gordon
HealthDay Reporter

TUESDAY, July 10 (HealthDay News) -- Although hastily created in response to the pandemic threat posed by the H1N1 flu virus, the vaccine for H1N1 is safe, even for expectant mothers and their babies, new studies show.

A Danish study that included more than 53,000 pregnant women, 13 percent of whom received the H1N1 vaccine, found no increased risk of major birth defects or pregnancy problems.

"We compared the vaccinated with the unvaccinated pregnancies with respect to a number of adverse events -- major birth defects, premature birth and fetal growth problems. None of these adverse events were more common among H1N1-vaccinated pregnancies. We conclude that H1N1-vaccinated pregnancies are not at increased risk of these adverse events," said Dr. Anders Hviid, a senior investigator at Statens Serum Institut, in Copenhagen.

Results of the study are published in the July 11 issue of the Journal of the American Medical Association.

The first case of H1N1 influenza was diagnosed in the United States in April 2009. This new flu was declared a pandemic flu in mid-June 2009. By mid-October, health officials had created and manufactured enough H1N1 vaccine to begin immunizing people at highest risk of complications and death from H1N1. By December 2009, the vaccine was widely available.

Pregnant women were among the high-priority groups, but safety data on the potential effects on fetuses were limited. However, the risks of contracting H1N1 during pregnancy were considered more severe, and the benefits of the vaccine appeared to outweigh any potential risk. More than 2.4 million American women were vaccinated against H1N1, according to the study.

In the current study, no difference in birth weights was detected among babies whose moms got the H1N1 vaccine during pregnancy and no increase in major birth defects was apparent in babies up to 1 year, the authors said.

Hviid noted that while this study adds to the literature on the safety of influenza vaccines in pregnancy, it isn't a complete evaluation of vaccines in pregnancy. "We cannot recommend specific courses of action based only on our study. However, our results are certainly reassuring to pregnant women and medical professionals," Hviid said.

Also, while the data on vaccination in the second and third trimesters provides "robust evidence of safety," the authors said the findings on first-trimester vaccination are considered preliminary and need confirmation.