A study described by some as puzzling, of pregnancies in the U.S., found that women who miscarried from 2010 to 2012 were more apt to have had flu vaccines for two straight years that included protection from swine flu.
Experts in vaccines believe the study’s results might reflect older age and other risks of miscarriage for women, and not the vaccine for flu. Health officials said there was no reason to change the recommendations by the government that all women who are pregnant receive a flu vaccination.
The officials said the flu itself was much more of a danger to pregnant women and the fetuses they were carrying.
The Center for Disease Control contacted a doctor’s group to warn them that the study was coming out and to help prepare them for a possible increase in concern by expectant mothers, said CDC officials.
Prior studies have found that flu vaccines were safe for pregnant women, although there has not been much research on the impact of the flu vaccine given during the first 90 days of pregnancy
Flu and the complications from it kill thousands each year in the U.S. with young children, the elderly and pregnant women under additional risk. When a new strain of swine flu emerged during 2009 it killed 56 pregnant women in the U.S. said data from the CDC.
The authors of the new study, two of whom are researchers for the CDC, saw a substantial difference when looking at women who miscarried within 28 days of receiving a flu shot that included swine flu protection, but it was only during the time that women also received a flu shot the year before.
Researchers found that 17 of the 485 miscarriages studies involved women that had vaccinations that followed that same pattern. Only four of the comparable 485 healthy pregnancies had involved women that were vaccinated in that manner.
The first group contained more women that were at higher risk of suffering a miscarriage such as older mothers, smokers, and those that had diabetes.
The researchers from the study attempted to make adjustments to the statistics to level some of the difference out, but some researchers do not think there was success.
Other medical experts said they could not believe that a shot made of killed flu virus would trigger a response from the immune system so severe it would create a miscarriage.
The authors said as well that they could not rule out a possible exposure to the swine flu itself that was a factor in prompting some of the miscarriages.