[ad_1]
A A new study to determine if pregnant women are at increased risk of miscarriage if they get a flu shot has not revealed any connection between the vaccine and the pregnancy loss.
This reassuring discovery contradicts an earlier study by the same researchers that raised questions about the safety of influenza vaccine during pregnancy. An overview of the results of the study was presented Wednesday at a meeting of the Advisory Committee on Immunization Practices, which guides the vaccination policy of Centers for Disease Control and Prevention.
The new study was larger than the first and specifically designed to address this issue, leading researchers to express their confidence in new discoveries. They will submit the data to a peer-reviewed journal for publication.
publicity
"For women who are currently wondering whether it is safe to be vaccinated in early pregnancy, it can be said unequivocally:" Yes, that's for sure, "said Dr. Edward Belongia, who was doing part of the research team. Center for Clinical Epidemiology and Population Health at the Marshfield Clinic in Wisconsin.
This is the third time that Belongia's group has addressed the issue. The first study, based on data from 2005-2006 and 2006-2007, revealed no association between influenza vaccines and miscarriages.
After the 2009 pandemic, however, the CDC asked the group to revisit the issue. The reason: The virus that caused this pandemic, a new type of H1N1 virus, became part of the annual influenza vaccine for the first time in the 2010-2011 season. The CDC wanted to make sure that what was true before remained so.
To everyone's surprise, the second study, published in 2017, raised a curious red flag. Some pregnant women who received a flu shot appeared to be at a higher risk of miscarriage, but only those who were vaccinated in the 28 days prior to their miscarriage – and the year before. Women who had been vaccinated only in the year of pregnancy did not appear to be at increased risk.
All studies were conducted using an observation model, which means that researchers looked at data from pregnant women who chose to be vaccinated or not. This type of study does not allow to determine the causal link. It can not be inferred that anything – in this case an early influenza vaccine in early pregnancy – appears to have been associated with a high risk of miscarriage.
Observational studies should be viewed with some caution, as there could be unanticipated confounding factors – factors that influence the outcome. In the case of the previous study, Belongia stated that it was possible that the association that had been identified was actually false – a statistical fluke caused by an unrecognized confounding factor.
The first study was small, only 485 women. And the number of women in the group where the association seemed to be occurring was minimal – there were only 14 women who had been vaccinated two years in a row and had miscarried. When the numbers are so low, interpret the results with caution.
The last study was about three times more women, said James Donahue, who led the study.
"This is good news," said Donahue.
[ad_2]
Source link