Pregnant Women can Receive the Influenza Vaccine Without Worry

A recent study reassures mothers who received the influenza vaccine while they were pregnant.

According to researchers from the University of California, San Diego School of Medicine and Boston University, in collaboration with the American Academy of Allergy Asthma and Immunology (AAAAI), they found evidence of the HINI influenza's safety during pregnancy.

"The overall results of the study were quite reassuring about the safety of the flu vaccine formulations that contained the pandemic H1N1 strain," said Christina Chambers, PhD, MPH, Director of the non-profit Organization of Teratology Information Specialists (OTIS) Research Center and lead investigator of UC San Diego's team, via a press release. "We believe our study's results can help women and their doctors become better informed about the benefits and risks of flu vaccination during pregnancy."

Though federal health authorities' had previously recommended that pregnant women receive the influenza vaccine, it's estimated that less than 50 percent of women follow this advice because they fear it could harm the development of their child.

As the researchers anticipate that the 2009 H1N1 influenza season would be severe, a national study was launched by the Vaccines and Medications in Pregnancy Surveillance System (VAMPSS), a collaboration between UC San Diego School of Medicine and Boston University that was coordinated with the AAAAI to gather data regarding the safety of the vaccine during pregnancy.

The researchers followed 1,032 pregnant women across the United States and Canada who either received the vaccine or did not from 2009 to 2012. The participants were recruited through the MotherToBaby, a service of OTIS.

The results include the following, via a press release: "Chamber's team found that women vaccinated during pregnancy were no more likely to experience miscarriage, have a baby born with a birth defect or have a baby born smaller than normal compared with those who did not receive a vaccination. Although vaccinated women were more likely to have their babies before term, on average these infants were delivered three days earlier than those born to unvaccinated women.

"The VAMPSS team from Boston University's Slone Epidemiology Center interviewed 4,191 mothers from four regional centers in the United States, who had either delivered a baby with one of 41 specific birth defects or delivered a normal infant. They compared the use of influenza vaccine in the two groups during the 2009-2011 seasons. The team also compared the risk of preterm delivery in vaccinated versus unvaccinated women. Overall, no significant evidence of an increased risk of any specific birth defects was noted. While the team did observe a slight increase in preterm delivery rates among pregnant women who received the H1N1 vaccine specifically during the 2009-2010 season, vaccinated women overall only delivered an average of two days earlier compared to the unvaccinated group. For those vaccinated during 2010-2011, the situation was reversed, and vaccinated women were less likely to deliver a preterm baby."

More information regarding the study can be found via the journal Vaccine.