Flu shot lowers odds for preemies; study highlights dangers of confusing anecdotes with data

PLoS Medicine has a new study out by Saad Omer, an assistant professor of global health, epidemiology and pediatrics at Emory University Schools of Public Health & Medicine. It has some potentially important news for pregnant women. Some of the key points are outlined in this write-up:

Women who gave birth when there were some, but not widespread, reports of flu were 56 percent less likely to have a premature baby than unvaccinated women. During peak flu season, generally January and February, pregnant women who got the flu shot were 72 percent less likely to deliver prematurely.

The study, published May 31 in PLoS Medicine, also found a slight association between flu vaccine and protection from “small for gestational age” babies (a birth weight, head circumference or length in the bottom 9 percent) during peak flu season, but not at other times. …

Infections during pregnancy can affect fetal growth and development, according to background information in the article. Respiratory infections, particularly pneumonia, are associated with low birth weight and increased risk of pre-term birth.

Influenza is particularly dangerous for pregnant women, who have a greater risk of serious illness and death. “There is a lot of evidence that flu is much more severe in pregnant women than in women of a similar age who are not pregnant,” Saad said.

Toward the end of pregnancy, women’s lung capacity decreases, and the heart must work harder to pump blood to support the fetus, which taxes the body. Pregnancy may also make it more difficult for the immune system to mount a response to the flu.

Babies born during peak flu season to mothers who were vaccinated against flu were 69 percent less likely to be small for their gestational age, the researchers found.

“The effect is significant during the flu period, and it goes up along with the intensity of flu circulation,” said lead study author Saad B. Omer…

I have no doubt in my mind that the legitimacy of the study will come under fire by anti-vaccine activists; reactions of groups like Generation Rescue and SafeMinds to various research conducted over the past decade have made it abundantly clear that there are pockets of fervent believers who will mistrust anything that doesn’t validate what they already believe to be true.

But this study is an example of why the rest of the population — that vast majority that isn’t on one extreme or the other — should be extremely careful about where they get their information. Parent forums, anecdotes picked up at playgroups, rumors about what happened to someone’s sister’s best friend, pseudo-studies gussied up to look like legitimate science — those are not ideal places to get advice about what’s best for your (or your family’s) health. (The Internet is particularly dangerous in this regard because a couple of extremely vocal people can end up sounding like a mob; that phenomena, which I wrote about in some length in my book, oftentimes leads to what’s referred to as an availability cascade.)

If future research upholds Omer’s initials results — and there are already reasons to indicate that it will — the risks posed to pregnant women who skip flu shots out of some misplaced fear about vaccine reactions are potentially severe indeed.

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