For years pregnant women have been having second thoughts on whether it’s safe for them to take the flu vaccine for fear that doing so would cause them to miscarriage. The default consensus among scientists is that the vaccine is completely safe for pregnant women, and are in fact recommended to reduce the risk of influenza, which has been proven to cause birth defects.
In a new study published Wednesday in the journal Vaccine, scientists have found the first potential link between flu vaccines and miscarriage early in pregnancy, specifically among pregnant women who received the flu vaccine for two years in a row, Washington Post reports. The findings, however, suggest an association, not a causal link, meaning that other variables may have caused the potential link to manifest itself in the study.
“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,” said Amanda Cohn, senior adviser for vaccines at the Centers for Disease Control and Prevention, which funded the new study.
The research is in its early stages and is therefore inconclusive. As such, experts are standing by their original assertion — that pregnant women should take the flu vaccine since it gives them a better chance at delivering their baby without serious health complications.
That said, researchers are looking to pursue further studies to determine if they can find other causal links between flu vaccines and miscarriages.
In light of the new findings, researchers are urging pregnant women to talk with their healthcare providers before getting the flu shot. They also emphasized that the new study does not provide sufficient reason to avoid the flu vaccine.
“Science is an incremental process, and a lot of people don’t understand that very seldom does a single study provide a definitive answer that can lead to changes in recommendations,” said Edward Belongia, a senior epidemiologist at the Marshfield Clinic Research Institute in Wisconsin and one of the study’s authors.
In the study, scientists at Marshfield compared 485 pregnant women (ages 18 to 44) who had miscarried to 485 women of a similar age bracket who had normal deliveries during the flu seasons of 2010-2011 and 2011-2012. Seventeen of the women who miscarried had received the flu vaccine in the 28 days before the miscarriage and had been immunized before the flu season. Majority of the miscarriages occurred in the first trimester of pregnancy, while some occurred during the second trimester.
By comparison, four of the women who had normal deliveries had received the flu vaccine in the preceding 28 days and had also been vaccinated during the prior flu season.
“We only saw the link between vaccination and miscarriage if they had been vaccinated in the season before,” said epidemiologist and lead author James Donahue.
The CDC is expected to study and investigate pregnant women who received the flu vaccine during three previous flu seasons, starting in 2012. Results are expected to be released late next year or in 2019.
“This is exactly why we study these things to make sure vaccines are safe and effective,” Cohn of the CDC.
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