For many years, pregnant women have been given the same, clear message at the start of flu season: The flu shot is a safe, effective way to avoid getting sick with no risk for a developing fetus. That message — backed by several large-scale studies conducted by the Centers for Disease Control and Prevention as well as other expert health agencies — was called into question last week when a new study seemed to point to a link between the influenza vaccine and early miscarriage in some women. But even in light of those new findings — along with a strong disclaimer that much more research is still needed in this area — doctors and experts are still urging pregnant women to get the flu shot this season, according to a new NPR report.
The American College of Obstetricians and Gynecologists, for instance, quickly published a statement to remind both women and their physicians that the flu shot is essential:
In evaluating all of the available scientific information, there is insufficient information to support changing the current recommendation which is to offer and encourage routine flu vaccinations during pregnancy regardless of the trimester of pregnancy.
But, let's back up a bit. How did the health community get here and why is the safety of the flu vaccine during pregnancy up for debate?
According to a segment this week on NPR's Morning Edition, the CDC published a study a few years back examining the relationship between flu vaccines and early miscarriage. In it, the research team looked at women who received the vaccine and were pregnant between 2005 and 2007. That study found no association between the flu shot and early pregnancy loss, NPR reported.
So, why the need for a second study? Lead author James Donahue, a senior epidemiologist at the Marshfield Clinic, told NPR that it was because after the 2009 H1N1 pandemic, the formulation of the flu vaccine changed. Once pregnant women started receiving a different vaccine, the team needed to conduct the study again.
“The CDC was very interested to make sure that we were still seeing the same safety profile for this new vaccine,” Donahue told Morning Edition. “And so [they] asked us to do another study.”
Still, the researchers told The Washington Post they were surprised by what the second study uncovered. According to that report, the same research team looked at the cases of nearly 1,000 women over two flu seasons to determine if there was any possible link between the influenza vaccine and early pregnancy loss.
This time, however, the team surveyed patients after the vaccine formula changed to respond to H1N1; the study included 485 pregnant patients, age 18-44, and 485 women who experienced miscarriages during the 2010-11 and 2011-12 flu seasons, according to The Washington Post. Of the women who had an early pregnancy loss, 17 had reportedly gotten the flu vaccine in the 28 days beforehand and in the prior flu season. Of the women who went on to deliver, only four who had gotten the vaccine in the 28 days prior to being surveyed also got the shot in the prior flu season.
The connection was weak, the researchers told The Washington Post, but well worth further study. Amanda Cohn, senior adviser for vaccines at the CDC told the newspaper that it was important for the team to offer patients full disclosure of potential risk, even if the exact connection wasn’t yet clear. According to The Washington Post, Cohn said:
I think it’s really important for women to understand that this is a possible link, and it is a possible link that needs to be studied and needs to be looked at over more [flu] seasons. We need to understand if it’s the flu vaccine, or is this a group of women [who received flu vaccines] who were also more likely to have miscarriages.
To help patients who might have concerns, the CDC has posted guidance on its website to specifically address the findings in this latest study.
Although this study quickly caused an uproar among anti-vaxxers and concerned expectant mothers, doctors are still urging pregnant women to get a flu shot each season because contracting the flu during pregnancy can be far more serious.
In its guidelines for protecting women from the flu during pregnancy, the March of Dimes website outlined the intense stress that pregnancy places on the body. For starters, when you’re pregnant, your immune system doesn’t respond as rapidly to disease, according to the March of Dimes website. And so, in pregnant women the symptoms of the flu can become severe much more quickly. Fever, dehydration, and other common concerns can become dangerous if a woman is pregnant, according to the CDC, making it more likely that pregnant women who get the flu will be hospitalized.
With all that in mind, the message from both the CDC and the American College of Obstetricians and Gynecologists is clear: Pregnant women should receive the flu vaccine this year and every year after, unless new, concrete evidence gives a reason to advice something different.
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