For Release

September 23, 2013

Megan Brown
(414) 272-6071

AAAAI Collaboration with UC San Diego and Boston University Publishes ‘Reassuring’ Data on H1N1 Influenza Vaccine Safety in Pregnancy


Two papers in Vaccine are the first published data from a national system designed to monitor the use and safety of certain vaccines and asthma medications during pregnancy

A national study by the Vaccines and Medications in Pregnancy Surveillance System (VAMPSS), a collaboration between the American Academy of Allergy, Asthma and Immunology (AAAAI) and investigative teams at UC San Diego and Boston University, has found ‘reassuring’ evidence of the H1N1 influenza vaccine’s safety during pregnancy. Launched shortly after the pandemic H1N1 influenza outbreak of 2009 and funded by the U.S. Department of Health and Human Services Biomedical Advanced Research and Development Authority (BARDA), the study will be presented in two companion papers published online this month in the Elsevier journal, Vaccine.

It is estimated that fewer than 50% of women follow federal health authorities’ recommendation that all pregnant women receive the influenza vaccine to avoid serious complications from flu infection. This is largely because of concerns about the effects flu vaccines might have on the developing baby. “Most vaccines and medications cannot be tested in pregnant women using clinical trials, so VAMPSS uses two data collection approaches to fill a critical gap in evaluating their safety,” said Michael Schatz, MD, MS, FAAAAI, who initiated the VAMPSS project and is the lead investigator for VAMPSS from AAAAI. “The papers in Vaccine highlight the ability of VAMPSS to utilize complementary research approaches to provide comprehensive safety information regarding the use of vaccines and medication in pregnancy,” he added.

The UC San Diego investigative team followed 1,032 pregnant women across the United States and Canada who either received an influenza vaccine or were not vaccinated during one of the three seasons from 2009 to 2012. Women were recruited through MotherToBaby, a service of the non-profit Organization of Teratology Information Specialists (OTIS). Data analysis 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. In addition, those who were vaccinated delivered infants three days earlier than unvaccinated women. (Read the abstract here.)

“The overall results of the study were quite reassuring about the safety of the flu vaccine formulations that contained the pandemic H1N1 strain given in these three seasons,” said Christina Chambers, PhD, lead investigator of UC San Diego’s team. “We believe our study’s results can help women and their doctors become better informed about the benefits and risks of vaccination during pregnancy.”

The research team from Boston University (BU) interviewed 4,191 mothers from four U.S. regional centers who had either delivered a baby with one of 41 specific birth defects or delivered an infant without defects. They compared the use of influenza vaccine in the two groups during the 2009 to 2011 seasons. In their analysis of birth defects, Carol Louik, ScD, lead investigator of the BU team, stated, “We found no evidence of an increase in risk for the most commonly-occurring specific major birth defects, which were the focus of the study, if a woman received the flu shot in pregnancy. Concerns about the risk of specific birth defects was a critical question that has not been considered very much until now, and our data are reassuring.” (Read the abstract here).

The team also compared the risk of preterm delivery in vaccinated versus unvaccinated women. While the team did observe a slight increase in preterm delivery rates among pregnant women who received the H1N1 vaccine specifically during the 2009 to 2010 season, vaccinated women overall only delivered an average of two days earlier compared to the unvaccinated group. For those vaccinated during the 2010 to 2011 season, the situation was reversed, and vaccinated women were less likely to deliver a preterm baby.

Since it was anticipated that the 2009 pandemic H1N1 influenza outbreak could be particularly severe, it was important to gather data on the safety of this vaccine in pregnancy. To do that, VAMPSS was established in 2010 under the umbrella of the AAAAI, a professional organization dedicated to the advancement of the knowledge and practice of allergy, asthma and immunology for optimal patient care. The AAAAI website provides additional information on VAMPSS.

The AAAAI represents allergists, asthma specialists, clinical immunologists, allied health professionals and others with a special interest in the research and treatment of allergic and immunologic diseases. Established in 1943, the AAAAI has more than 6,700 members in the United States, Canada and 60 other countries. The AAAAI’s Find an Allergist / Immunologist service is a trusted resource to help patients find a specialist close to home.


Notes for Editors:

 “Risks and Safety of Pandemic H1N1 Influenza Vaccine in Pregnancy: Birth Defects, Spontaneous Abortion, Preterm Delivery, and Small for Gestational Age Infants” doi: 10.1016/j.vaccine.2013.08.097 (pp. 5058-5064); Vaccine, published by Elsevier.

“Risks and Safety of Pandemic H1N1 Influenza Vaccine in Pregnancy: Exposure Prevalence, Preterm Delivery, and Specific Birth Defects” doi: 10.1016/j.vaccine.2013.08.096 (pp. 5065-5072); Vaccine, published by Elsevier.

Copies of these papers are available to credentialed journalists upon request; please contact

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