Exposure to 2009 pH1N1 Vaccine During Pregnancy Seems Safe

Exposure to the 2009 pandemic H1N1 (pH1N1) influenza vaccine in pregnancy is not associated with most negative health outcomes among offspring, according to a study published online in The BMJ.

Laura K. Walsh, from the Better Outcomes Registry & Network in Ottawa, Ontario, Canada, and colleagues conducted a retrospective cohort study involving 104,249 live births from November 2009 through October 2010 in Ontario to examine whether there was any correlation between exposure to 2009 pH1N1 influenza vaccination during pregnancy and negative health outcomes. Children were followed until age 5 years for study outcomes.

The researchers note that 30 percent of the live births were exposed to pH1N1 influenza vaccination in utero. No significant correlations were found between pH1N1 influenza vaccination in utero and upper or lower respiratory infections, otitis media, any infectious diseases, neoplasms, sensory disorders, urgent and inpatient health service use, pediatric complex chronic conditions, or mortality. Prenatal pH1N1 vaccination was weakly associated with an increased risk for asthma (adjusted hazard ratio, 1.05) and with decreased rates of gastrointestinal infections (adjusted incidence rate ratio, 0.94). In sensitivity analyses accounting for any potential differential health care-seeking behavior or access between exposure groups, the results were unchanged.

"Although we observed a small, but statistically significant, increase in pediatric asthma and a reduction in gastrointestinal infections, we are not aware of any biologic mechanisms to explain these findings," the authors write.

One author disclosed financial ties to the pharmaceutical industry.

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