Influenza Pandemics-Pregnancy, Pathogenesis, and Perinatal Outcomes

JAMA The Journal of the American Medical Association (Impact Factor: 35.29). 07/2012; 308(2):184-5. DOI: 10.1001/jama.2012.7911
Source: PubMed
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    ABSTRACT: As pregnant women are considered a high-risk group for severe influenza illness, current recommendations advise vaccination of all pregnant women with inactivated influenza vaccine. Nevertheless, rates of maternal influenza vaccination have historically been low, possibly reflecting ongoing concerns about vaccine safety. Until recently, the majority of evidence concerning safety of influenza vaccination during pregnancy was limited to post-marketing pharmacovigilance studies; however, in the past 5 years, one randomized clinical trial and a number of observational studies reflecting seasonal trivalent inactivated influenza vaccines and monovalent H1N1 influenza vaccines have been published. This review summarizes the evidence pertaining to fetal and neonatal outcomes following influenza vaccination during pregnancy for comparative analytic studies published between 2008 and August 2013. Since the majority of these studies are observational in nature, issues related to study quality are also addressed.
    Expert Review of Vaccines 12/2013; 12(12):1417-30. DOI:10.1586/14760584.2013.851607 · 4.21 Impact Factor
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    ABSTRACT: 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.
    BMJ Clinical Research 05/2014; 348(may29 5):g3361. DOI:10.1136/bmj.g3361 · 14.09 Impact Factor
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    ABSTRACT: Background Before 2012, few studies had addressed pregnancy outcomes following maternal influenza vaccination; however, the number of publications on this topic has increased recently.Objectives To review comparative studies evaluating fetal death or preterm birth associated with influenza vaccination during pregnancy.Search strategyWe searched bibliographic databases from inception to April 2014.Selection criteriaExperimental or observational studies assessing the relationship between influenza vaccination during pregnancy and fetal death or preterm birth.Data collection and analysisTwo reviewers independently abstracted data from studies meeting the inclusion criteria.Main resultsWe included one randomised clinical trial and 26 observational studies. Meta-analyses were not considered appropriate because of high clinical and statistical heterogeneity. Three studies of fetal death at any gestational age reported adjusted effect estimates in the range 0.56–0.79, and four of five studies of fetal death at <20 weeks reported adjusted estimates between 0.89 and 1.23, all with confidence intervals including 1.0. Adjusted effect estimates for four of five studies of fetal death at ≥20 weeks ranged from 0.44 to 0.77 (two with confidence intervals not crossing 1.0), whereas a fifth reported a non-significant effect in the opposite direction. Among 19 studies of preterm birth, there was no strong evidence suggesting any increased risk, and meta-regression did not explain the moderate between-study heterogeneity (I2 = 57%).Authors' conclusionsMost studies reported no association between fetal death or preterm birth and influenza vaccination during pregnancy. Although several reported risk reductions, results may be biased by methodological shortcomings of observational studies of influenza vaccine effectiveness.
    BJOG An International Journal of Obstetrics & Gynaecology 07/2014; 122(1). DOI:10.1111/1471-0528.12977 · 3.45 Impact Factor
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