Pandemic A/H1N1 influenza vaccination during pregnancy: a comparative study using the EFEMERIS database

Area of Science:

• Obstetrics and Gynecology
• Infectious Disease Epidemiology
• Vaccinology

Background:

• Influenza A/H1N1 pandemic vaccination campaigns included pregnant women, necessitating safety evaluations.
• Assessing the impact of A/H1N1 vaccination on pregnancy outcomes is crucial for public health recommendations.

Purpose of the Study:

• To determine the risk of adverse pregnancy outcomes associated with A/H1N1 vaccination in pregnant women.
• To compare pregnancy loss, preterm delivery, small for gestational age (SGA), and neonatal pathology rates between vaccinated and unvaccinated pregnant individuals.

Main Methods:

• An observational cohort study utilized the French EFEMERIS prescription database.
• Pregnant women ending pregnancies between October 2009 and November 2010 were included, with 2:1 matching of unvaccinated to vaccinated women.
• Conditional logistic regression and Cox proportional hazards models analyzed associations between A/H1N1 vaccination and adverse outcomes.

Main Results:

• No significant differences in pregnancy loss, preterm birth, or neonatal pathology were observed between vaccinated (n=1645) and unvaccinated (n=3290) groups.
• The rate of small for gestational age (SGA) was significantly lower in the vaccinated group (0.5% vs. 1.4%).
• Most vaccinations occurred in December 2009 using non-adjuvanted vaccines.

Conclusions:

• Non-adjuvanted A/H1N1 vaccination during pregnancy is not associated with an increased risk of adverse pregnancy outcomes.
• The findings support the safety of A/H1N1 vaccination for pregnant women regarding major adverse pregnancy events.