Evaluation of safety of A/H1N1 pandemic vaccination during pregnancy: cohort study

British Medical Journal
07 June 2014 (Vol 348, Issue 7961)

H1N1 influenza vaccination during pregnancy
Deshayne B Fell, perinatal epidemiologist1, Linda Dodds, professor of obstetrics and gynecology and paediatrics2, Shelly McNeil, associate professor of medicine3, Noni E MacDonald, professor of pediatrics and microbiology and immunology3
H1N1 safety data look reassuring, but we need ongoing surveillance of all influenza vaccines given to pregnant women
to pregnant women from influenza infection have long been recognized.1 The recent 2009-10 H1N1 pandemic was no exception—pregnant women were at higher risk of severe H1N1 influenza illness compared with the general population,2 and those with H1N1 influenza had higher rates of adverse pregnancy outcomes than did uninfected pregnant women.3 Despite limited safety data for use of the monovalent H1N1 vaccines in pregnancy, pregnant women were widely prioritized for H1N1 vaccination programs.4 Fortunately, enhanced surveillance of pregnant women during the pandemic has enabled retrospective evaluation of the safety of monovalent H1N1 vaccine in obstetric populations around the world…

Evaluation of safety of A/H1N1 pandemic vaccination during pregnancy: cohort study
BMJ 2014; 348 doi: http://dx.doi.org/10.1136/bmj.g3361 (Published 29 May 2014)
Cite this as: BMJ 2014;348:g3361
Objective To assess the risk of maternal, fetal, and neonatal outcomes associated with the administration of an MF59 adjuvanted A/H1N1 vaccine during pregnancy.
Design Historical cohort study.
Setting Singleton pregnancies of the resident population of the Lombardy region of Italy.
Participants All deliveries between 1 October 2009 and 30 September 2010. Data on exposure to A/H1N1 pandemic vaccine, pregnancy, and birth outcomes were retrieved from regional databases. Vaccinated and non-vaccinated women were compared in a propensity score matched analysis to estimate risks of adverse outcomes.
Main outcome measures Main maternal outcomes included type of delivery, admission to intensive care unit, eclampsia, and gestational diabetes; fetal and neonatal outcomes included perinatal deaths, small for gestational age births, and congenital malformations.
Results Among the 86,171 eligible pregnancies, 6246 women were vaccinated (3615 (57.9%) in the third trimester and 2557 (40.9%) in the second trimester). No difference was observed in terms of spontaneous deliveries (adjusted odds ratio 1.02, 95% confidence interval 0.96 to 1.08) or admissions to intensive care units (0.95, 0.47 to 1.88), whereas a limited increase in the prevalence of gestational diabetes (1.26, 1.04 to 1.53) and eclampsia (1.19, 1.04 to 1.39) was seen in vaccinated women. Rates of fetal and neonatal outcomes were similar in vaccinated and non-vaccinated women. A slight increase in congenital malformations, although not statistically significant, was present in the exposed cohort (1.14, 0.99 to 1.31).
Conclusions Our findings add relevant information about the safety of the MF59 adjuvanted A/H1N1 vaccine in pregnancy. Residual confounding may partly explain the increased risk of some maternal outcomes. Meta-analysis of published studies should be conducted to further clarify the risk of infrequent outcomes, such as specific congenital malformations.