Health officials say that there is no reason to change the government with the recommendation that all pregnant women be vaccinated against the flu.
NEW YORK – A puzzling study of U.S. births found that women who have miscarriages between 2010 and 2012 were more likely to have had back-to-back annual flu shots that protect against the swine flu.
Vaccine experts believe that the results may reflect the older age and other miscarriage risks for women, and not the flu shots. Health officials say that there is no reason to change the government with the recommendation that all pregnant women be vaccinated against the flu. They say that the flu is a much greater danger for the women and their fetuses.
The Centers for Disease Control and Prevention has reached out to a physician group, the American Congress of Obstetricians and Gynecologists, to warn them for the study is coming out and help them to prepare for a possible wave of the worries of expectant mothers, CDC officials said.
“I want the CDC and researchers to continue to investigate,” said Dr. Laura Riley, a Boston-based obstetrician who leads a committee maternal immunization. “But as an advocate for pregnant women, which I hope does not happen is that people panic and stop getting vaccinated.”
Previous studies have found flu vaccines are safe during pregnancy, but there is little research on the effects of flu vaccinations given in the first three months of pregnancy.
This study focused only on miscarriages, which are located in the first 19 weeks of the pregnancy and are common. As many as half of the pregnancies ends in a miscarriage, according to a March of Dimes estimate that attempts to cases in which the miscarriage occurs before a women even realizes she was pregnant.
Flu and its complications kill thousands of Americans every year. The elderly, young children and pregnant women are particularly at risk. When a new “swine flu” strain originated in 2009, killed 56 US pregnant women that year, according to the CDC.
The authors of the study, two of whom are CDC researchers saw a big difference when they looked at women who had a miscarriage within 28 days after getting a shot that under the protection against the swine flu, but it was only when the women also had a flu shot the previous season.
They found 17 of 485 abortions they studied involved women whose vaccinations follows that pattern. Only four of a similar 485 healthy pregnancies involved women who have been vaccinated that way.
The first group also had more women who have a higher risk of miscarriage, such as older mothers, smokers and people with diabetes. The researchers attempted to make statistical adjustments to the level of some of these differences, but some researchers don’t think they fully succeeded.
Other experts say that they do not believe that there is a recording made from killed flu virus could lead to a immune system severe enough to prompt a miscarriage. And the authors said they could not rule out the possibility that exposure to the swine flu itself was a factor in some miscarriages.
Two other medical journals rejected the article for a third, Vaccine, accepted it. Dr. Gregory Poland, Vaccine editor-in-chief, said that it is a well-designed study showed that a question that should not be ignored. But he does not believe flu shots are the cause of the miscarriages. “Not at all,” said Poland, who is also director of the vaccine research at the Mayo Clinic.
Although this research can lead to worry and confusion, is the evidence of how strict and principled us vaccine safety monitoring system,” said Jason Schwartz, a Yale University vaccine policy expert.
A number of the same researchers are working on a larger study looking at more recent data to see if a possible link between the swine flu vaccine and has a miscarriage, said James Donahue, a study author from the Wisconsin-based Marshfield Clinic Research Institute. The results are not expected until next year at the earliest, he said.
This story has been corrected to say that Marshfield Clinic Research Institute is located in Wisconsin.