Risk of Fetal Death After Pandemic Influenza Virus Infection or Vaccination

and the London School of Hygiene and Tropical Medicine, London (A.S.).
New England Journal of Medicine (Impact Factor: 55.87). 01/2013; 368(4). DOI: 10.1056/NEJMoa1207210
Source: PubMed


During the 2009 influenza A (H1N1) pandemic, pregnant women were at risk for severe influenza illness. This concern was complicated by questions about vaccine safety in pregnant women that were raised by anecdotal reports of fetal deaths after vaccination.

We explored the safety of influenza vaccination of pregnant women by linking Norwegian national registries and medical consultation data to determine influenza diagnosis, vaccination status, birth outcomes, and background information for pregnant women before, during, and after the pandemic. We used Cox regression models to estimate hazard ratios for fetal death, with the gestational day as the time metric and vaccination and pandemic exposure as time-dependent exposure variables.

There were 117,347 eligible pregnancies in Norway from 2009 through 2010. Fetal mortality was 4.9 deaths per 1000 births. During the pandemic, 54% of pregnant women in their second or third trimester were vaccinated. Vaccination during pregnancy substantially reduced the risk of an influenza diagnosis (adjusted hazard ratio, 0.30; 95% confidence interval [CI], 0.25 to 0.34). Among pregnant women with a clinical diagnosis of influenza, the risk of fetal death was increased (adjusted hazard ratio, 1.91; 95% CI, 1.07 to 3.41). The risk of fetal death was reduced with vaccination during pregnancy, although this reduction was not significant (adjusted hazard ratio, 0.88; 95% CI, 0.66 to 1.17).

Pandemic influenza virus infection in pregnancy was associated with an increased risk of fetal death. Vaccination during pregnancy reduced the risk of an influenza diagnosis. Vaccination itself was not associated with increased fetal mortality and may have reduced the risk of influenza-related fetal death during the pandemic. (Funded by the Norwegian Institute of Public Health.).

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    • "However, influenza has also been associated with adverse fetal outcomes including a higher risk of perinatal death, intrauterine growth restriction, and being born preterm [12]. In a recent Norwegian study of 117 347 pregnancies [13] "
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    ABSTRACT: Objective To study the uptake of influenza vaccination among pregnant women in northern India and physicians’ beliefs and practices regarding vaccination. Methods A questionnaire-based survey was undertaken between October 2012 and April 2013. Pregnant women attending an obstetric hospital in Srinagar, India, and healthcare personnel were asked to participate. Results Among 1000 women aged 18–41 years (13.6% first trimester, 26.8% second trimester), none had been offered or received influenza vaccination. Only 9 (10.0%) of 90 obstetricians surveyed had been vaccinated for influenza in the past 5 years, although 81 (90.0%) believed that influenza could have severe consequences for themselves and their patients. The reasons cited for non-vaccination included poor knowledge about availability of vaccine and concerns about its efficacy. Sixty-six (73.3%) obstetricians believed that vaccine adverse effects are under-reported, and 79 (87.8%) believed that vaccination programs are motivated by profit. Eighty-four (93.3%) obstetricians wished to undergo vaccination in the coming flu season. Conclusion Influenza vaccination among pregnant women in northern India is nonexistent. Poor uptake is rooted in misperceptions about vaccine availability, efficacy, and safety among treating physicians, few of whom are vaccinated.
    International Journal of Gynecology & Obstetrics 12/2014; DOI:10.1016/j.ijgo.2014.05.021 · 1.54 Impact Factor
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    • "The effectiveness ofAS03-adjuvanted split-virion H1N1 vaccine was demonstrated in pregnant women during the second and third trimesters in a cohort study in Norway. A total of 46 491 pregnant women were followed up during the pandemic wave, of which 54% were vaccinated [16]. 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]. "
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    ABSTRACT: Vaccine-preventable infectious diseases are responsible for significant maternal, neonatal, and young infant morbidity and mortality. While there is emerging scientific evidence, as well as theoretical considerations, indicating that certain vaccines are safe for pregnant women and fetuses, policy formulation is challenging because of perceived potential risks to the fetus. This report presents an overview of available evidence on pregnant women vaccination safety monitoring in pregnant women, from both published literature and ongoing surveillance programs. Safety data were reviewed for vaccines against diseases which increase morbidity in pregnant women, their fetus or infant as well as vaccines which are used in mass vaccination campaigns against diseases. They include inactivated seasonal and pandemic influenza, mono- and combined meningococcal polysaccharide and conjugated vaccines, tetanus toxoid and acellular pertussis combination vaccines, as well as monovalent or combined rubella, oral poliomyelitis virus and yellow fever vaccines. No evidence of adverse pregnancy outcomes has been identified from immunization of pregnant women with these vaccines.
    Vaccine 10/2014; 32(52). DOI:10.1016/j.vaccine.2014.09.052 · 3.62 Impact Factor
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    • "In pregnancies not affected by early loss, there has been an excess of adverse outcomes in women with influenza. In a Norwegian national registry study, there was an increased rate of fetal death among pregnancies complicated by 2009 H1N1 influenza.23 In a United Kingdom series of 256 women with 2009 H1N1 influenza, there was an increased perinatal mortality rate (39 per 1000 births compared to 7 per 1000 in women without influenza), stillbirth rate, and a fourfold increased likelihood of preterm birth.24 "
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    ABSTRACT: Influenza poses unique risks to pregnant women, who are particularly susceptible to morbidity and mortality. Historically, pregnant women have been overrepresented among patients with severe illness and complications from influenza, and have been more likely to require hospitalization and intensive care unit admission. An increased risk of adverse outcomes is also present for fetuses/neonates born to women affected by influenza during pregnancy. These risks to mothers and babies have been observed during both nonpandemic and pandemic influenza seasons. During the H1N1 influenza pandemic of 2009-2010, pregnant women were more likely to be hospitalized or admitted to intensive care units, and were at higher risk of death compared to nonpregnant adults. Vaccination remains the most effective intervention to prevent severe illness, and antiviral medications are an important adjunct to ameliorate disease when it occurs. Unfortunately, despite national guidelines recommending universal vaccination for women who are pregnant during influenza season, actual vaccination rates do not achieve desired targets among pregnant women. Pregnant women are also sometimes reluctant to use antiviral medications during pregnancy. Some of the barriers to use of vaccines and medications during pregnancy are a lack of knowledge of recommendations and of safety data. By improving knowledge and understanding of influenza and vaccination recommendations, vaccine acceptance rates among pregnant women can be improved. Currently, the appropriate use of vaccination and antiviral medications is the best line of defense against influenza and its sequelae among pregnant women, and strategies to increase acceptance are crucial. This article will review the importance of influenza in pregnancy, and discuss vaccination and antiviral medications for pregnant women.
    International Journal of Women's Health 07/2014; 6(1):681-689. DOI:10.2147/IJWH.S47235
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