Article

Pasternak, B. et al. Vaccination against pandemic A/H1N1 2009 influenza in pregnancy and risk of fetal death: cohort study in Denmark. BMJ 344, e2794

Department of Epidemiology Research, Statens Serum Institut, Artillerivej 5, 2300 Copenhagen, Denmark.
BMJ (online) (Impact Factor: 16.38). 05/2012; 344:e2794. DOI: 10.1136/bmj.e2794
Source: PubMed

ABSTRACT To investigate whether an adjuvanted pandemic A/H1N1 2009 influenza vaccine in pregnancy was associated with an increased risk of fetal death.
Nationwide register based cohort study.
Denmark.
All clinically recognised singleton pregnancies that ended between November 2009 and September 2010. Individual level data on exposure to an inactivated AS03 pandemic A/H1N1 2009 influenza vaccine (Pandemrix) and potential confounders were linked to the study cohort using a unique person identifier.
The primary outcome measure was risk of fetal death (spontaneous abortion and stillbirth combined) in H1N1 vaccinated compared with unvaccinated pregnancies, adjusting for propensity scores. Secondary outcome measures were spontaneous abortion (between seven and 22 weeks' gestation) and stillbirth (after 22 completed weeks' gestation).
The cohort comprised 54,585 pregnancies; 7062 (12.9%) women were vaccinated against pandemic A/H1N1 2009 influenza during pregnancy. Overall, 1818 fetal deaths occurred (1678 spontaneous abortions and 140 stillbirths). Exposure to the H1N1 vaccine was not associated with an increased risk of fetal death (adjusted hazard ratio 0.79, 95% confidence interval 0.53 to 1.16), or the secondary outcomes of spontaneous abortion (1.11, 0.71 to 1.73) and stillbirth (0.44, 0.20 to 0.94). Estimates for fetal death were similar in pregnant women with (0.82, 0.44 to 1.53) and without comorbidities (0.77, 0.47 to 1.25).
This large cohort study found no evidence of an increased risk of fetal death associated with exposure to an adjuvanted pandemic A/H1N1 2009 influenza vaccine during pregnancy.

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    • "In a small study in the United Kingdom, 77 pregnant women received AS03 adjuvant end vaccine in the second or third trimester; three-quarters of the newborn infants were found to have passive immunity at hemagglutination inhibition titers of 1:40 or greater consistent with clinical protection, as a result of transplacental transfer [43]. A study of a Danish cohort of approximately 7000 vaccinated pregnant women found no association between exposure to AS03- adjuvanted H1N1 monovalent vaccine during pregnancy and fetal death, preterm birth, major birth defects and fetal growth restriction [44] [45]. The data also provided preliminary evidence that excluded a high risk of adverse pregnancy outcomes in 345 women vaccinated in the first trimester because of pre-existing chronic diseases [46]. "
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