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

  1. Mary says:

    Although I’m not having babies, I also feel it’s my responsibility to *not* spread stuff like this to other people who are at risk. No matter how young and healthy I might be personally.

    Public health is everyone’s responsibility. A lot of people are unaware of that.

  2. Gregory James says:

    “… that vast majority that isn’t on one extreme or the other …”

    OK. I get that antivaxers are extreme. But I’m having trouble understanding who the what the other extreme position is.

  3. Mara says:

    Wait, I have an anecdote! Both of my kids were born during flu season (4 years apart) and I got the flu shot both times and they were still low birth weight preemies. This must prove the study is wrong ;)

    Seriously, though, my first pregnancy was during the flu season 6 years ago, when there were major shortages of the vaccine. I went from doctor to store to clinic trying to find a flu shot for myself, because I’d spent 5 years trying to get pregnant and I wasn’t going to lose that baby, damn it. Just as I was giving up hope, my parents’ doctor agreed to vaccinate me. I can’t tell you how relieved I was.

    Fortunately, the next time I was pregnant, there was no shortage and my daughter’s pediatrician gave me one at the same time. (I love that they do that, BTW, because it makes it convenient for me. I’ll happily pay for the convenience factor!)

    My kids get a flu shot every year in order to protect their grandparents from my darling little disease vectors :D

  4. Julia says:

    So I happened to check out the first link suggested in the auto-generated “You might also like” list that appeared right below this post… Melinda Wenner Moyer’s Why pregnant women deserve drug trials (posted 6 Jan 2011).

    In that post, the author discusses how she (pregnant herself) “struggled over the decision to get a flu shot” and concludes that her decision “was a gamble based on a lot of incomplete information”. This despite the fact that Melinda seems to have access to a lot more information than the average pregnant woman — for example, she mentions personal conversations with “Caltech biologist Paul Patterson”.

    Reading her post juxtaposed with yours felt really weird — if I had only read your post, I would have filed it away as “don’t be scared of vaccines — the flu vaccine improves the chance of a healthy pregnancy”. But if I had only read Melinda’s post, I would have left thinking “flu vaccine: a scary prospect for pregnant women!” Since I read both posts, I wound up feeling plain uncertain. Do the benefits of the flu vaccine highlighted in Seth’s post outweigh the risks highlighted in Melinda’s? Is Melinda even right about those risks, or have her fears been unnecessarily inflated? As someone who will hopefully one day be pregnant and have to make this decision, how scared should I be? Ack!

    Seth, I agree with you about the power of information sources in amplifying fear and unreason around already emotionally charged issues, and I like the really sharp points you’ve made about the vicious cycles that develop. I’d love to know what you think of Melinda’s post, especially its meta-message (“flu vaccine during pregnancy: scary!”). From a journalistic perspective, do you think that post does a reasonable job discussing the issue of flu-vaccines-when-pregnant, or does it (unwittingly) inflate fear around it? I’m not sure at all what I think — the post is not entirely anecdote, but it left me scared nonetheless.

  5. Gaythia says:

    I think that this post, amplified by the immediate example provided by Julia in her comment above, raises an important point regarding how the natural caution of pregnant women can be amplified into unwarranted fear by misinformation.

    But an important background issue here in the US are the abysmal statistics on unintended pregnancy. In an ideal situation, preparations for pregnancy should begin well before conception.

    If one of our objectives is to reduce the levels of premature births, we need to actively object to current efforts to reduce funding for women’s health care clinics. These clincs provide many women with the basic reproductive health care that allows for planned pregnancies and healthy babies. Even though it is true that flu shots are frequently developed so close to the season of use that they may still need to be given during a pregnancy, pregnant or about to be pregnant women need to be in close contact with health care providers in order to have questions answered and to be properly informed.

    Too often, I believe, science posts on vaccination are written from a perspective that focuses on refusal, without acknowledging the importance of access.

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