New study shows possible link between flu vaccine and miscarriage

A research center found a link between miscarriage and flu vaccinations during two flu seasons, but didn't find a link in two other ones.

As all mothers know, the vaccine debate rages on. It seems every year as back-to-school season revs up again, the "to vaccinate or not to vaccinate" issue is brought to light once again. A new study may have just added fuel to the fire, calling into question the safety of the flu vaccination for children yet to be born. According to a recent observational study published in the journal Vaccine, there is a possible link between the flu vaccine and miscarriage, The Washington Post reports.

Scientists at Marshfield Clinic Research Institute in Wisconsin compared 458 pregnant women aged 18 to 44 who had a miscarriage to 458 pregnant women of similar ages who had normal deliveries during the 2010/2011 and 2011/2012 flu seasons. Of the 458 women who miscarried, 17 had been vaccinated against the flu no more than 28 days before the miscarriage and were immunized during the 2010-2011 flu season. Of the 458 women who did not miscarry, four had received the flu vaccine in the preceding 28 days and were immunized during the 2010-2011 flu season.

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James Donahue, an epidemiologist and lead author of the study, explained that the link between vaccination and miscarriage was only present when the women had been vaccinated in both the 2010-2011 flu season and the 2011-2012 season.

The same research center in Wisconsin performed the study again using data from the 2005/2006 flu season and the following 2006/2007 flu season and found no link between flu vaccination and miscarriage.

Additionally, the study had several limitations, such as the small sample size and the possible biases. For example, the study's authors cited bias in the possibility that the women who sought medical care following their miscarriage perhaps were more likely to also be vaccinated against the flu. Some women, too, miscarry so early in their pregnancy that they are unaware they were pregnant at all. The authors also cited that women who regularly get vaccinated against the flu are more likely to be aware of their pregnancies and alert their healthcare provider of a miscarriage, which could explain the study's findings.

Thus, the CDC, the American College of Obstetricians and Gynecologists and the study's authors all urge pregnant women to continue getting the flu vaccine. The danger of getting influenza while pregnant is greater that the possible risk this study has revealed, and infants six months or younger are advised not to get the flu shot, so a mother's best choice is to be vaccinated while pregnant to protect the child and herself against influenza.

In anticipation of questions related to the study's possible link between vaccination and miscarriage, new guidelines have been posted by the CDC regarding pregnancy and the flu vaccination.

So for now, the great vaccine debate continues, albeit with more complexities, given the study's recent findings.