Risks and safety of pandemic H1N1 influenza vaccine in pregnancy: Exposure prevalence, preterm delivery, and specific birth defects

Vaccines and Medications in Pregnancy Surveillance System (VAMPSS), United States. Electronic address: .
Vaccine (Impact Factor: 3.62). 09/2013; 31(44). DOI: 10.1016/j.vaccine.2013.08.096
Source: PubMed


We estimated exposure prevalence and studied potential risks for preterm delivery (PTD) and specific birth defects associated with exposure to the unadjuvanted pH1N1-containing vaccines in the 2009-2010 and 2010-2011 influenza seasons. We used data from 4 regional centers in the United States collected as part of the Slone Epidemiology Center's Birth Defects Study. For PTD, propensity score-adjusted time-varying hazard ratios (HRs) and 95% confidence intervals (CIs) were estimated for exposure anytime in pregnancy and for each trimester. For 41 specific major birth defects, propensity score-adjusted odds ratios (ORs) and 95% confidence intervals (CIs) were estimated. Among 4191 subjects, there were 3104 mothers of malformed (cases) and 1087 mothers of nonmalformed (controls). Exposure prevalences among controls were 47% for the 2009-2010 season and 38% for the 2010-2011 season; prevalence varied by geographic region. Results for PTD differed between the two seasons, with risks above and below the null for the 2009-2010 and 2010-2011 seasons, respectively. For 41 specific birth defects, most adjusted ORs were close to 1.0. Three defects had adjusted ORs>2.0 and four had risks<0.5; however, 95% CIs for these were wide.
Among women exposed to pH1N1 vaccine, we found a decreased risk for PTD in the 2010-2011 season; risk was increased in 2009-2010, particularly following exposure in the first trimester, though the decrease in gestational length was less than 2 days. For specific major defects, we found no meaningful evidence of increased risk for specific congenital malformations following pH1N1 influenza vaccinations in the 2009-2010 and 2010-2011 seasons.

15 Reads
    • "Unvaccinated Effect Estimate (95% CI) Factors Controlled or Adjusted* Chambers et al, 2013 36 T1: 9/328 6/188 T1: aOR 0.79 (0.26–2.42) Age, BMI, race–ethnicity, socioeconomic status, smoking, alcohol, vitamin supplementation, pregnancy history, previous preterm delivery, infection, fever, asthma, depression, autoimmune disease, hypertension, and seasonal vaccine not containing the H1N1 2009 pandemic strain Louik et al, 2013 37, † 2009–2010: 709/1,750; 2010–2011: 642/ 1,868; 2009–2011: 1,351/3,618 2009–2010: 267/ 570; 2010–2011: 244/655; 2009– 2011: 511/1,225 2009–2010: OR 0.77 (0.64–0.93). 2010– 2011: OR 0.88 (0.73– 1.06). "
    [Show abstract] [Hide abstract]
    ABSTRACT: Objective: To systematically summarize the literature on maternal influenza vaccination and the risk for congenital malformations using the methodology of meta-analysis. Data sources: PubMed, Scopus, and Embase databases (up to December 2014) as well as (May 2015) and references of relevant articles were searched. The search strategy included combinations of the terms "influenza," "vaccin*," "pregnan*," "safe*," "adverse," "congenital," "malformation," "defect," and "anomal*." Methods of study selection: Eligible studies examined the association between antepartum or preconceptional maternal immunization with inactivated influenza vaccines (seasonal trivalent or monovalent H1N1) and the risk for congenital malformations. Studies with no or inappropriate control group (comparison with population background rates or other vaccine types) were excluded. Tabulation, integration, and results: The risk for congenital anomalies after influenza vaccination was examined in 15 studies: 14 cohorts (events per vaccinated compared with unvaccinated: 859/32,774 [2.6%] compared with 7,644/245,314 [3.1%]) and one case-control study (vaccinated per cases compared with controls: 1,351/3,618 [37.3%] compared with 511/1,225 [41.7%]). Eight studies reported on first-trimester immunization (events per vaccinated compared with unvaccinated: 258/4,733 [5.4%] compared with 6,470/196,054 [3.3%]). No association was found between congenital defects and influenza vaccination at any trimester of pregnancy (odds ratio [OR] 0.96, 95% confidence interval 0.86-1.07; 15 studies; I=36) or at the first trimester (OR 1.03, 0.91-1.18; eight studies; I=0). When assessing only major malformations, no increased risk was detected after immunization at any trimester (OR 0.99, 0.88-1.11; 12 studies; I=31.5) or at the first trimester (OR 0.98, 0.83-1.16; seven studies; I=0). Neither adjuvanted (OR 1.06, 0.95-1.20; five studies; I=18.8) nor unadjuvanted vaccines (OR 0.89, 0.75-1.04; seven studies; I=22.6) were associated with an increased risk for congenital defects. Conclusion: This systematic review did not indicate an increased risk for congenital anomalies after maternal influenza immunization adding to the evidence base on the safety of influenza vaccination in pregnancy.
    Obstetrics and Gynecology 10/2015; 126(5). DOI:10.1097/AOG.0000000000001068 · 5.18 Impact Factor
  • 6th Vaccine and ISV Annual Global Congress, Shanghai, China; 10/2012
  • [Show abstract] [Hide abstract]
    ABSTRACT: There is a need for additional information on the fetal risks and relative safety of the pandemic H1N1 monovalent or trivalent influenza (pH1N1)-containing vaccines in women exposed during pregnancy. To assess risks and relative safety of the pH1N1-containing vaccines, we conducted a prospective cohort study of pH1N1-vaccine-exposed and unexposed comparison women residing in the U.S. or Canada who were recruited during pregnancy and followed to outcome between October 2009 and August 2012. For exposure to the pH1N1 vaccine, adjusted relative risks (RRs) and 95% confidence intervals (CIs) were estimated for major birth defects and infants small for gestational age. Adjusted hazard ratios (HRs) and 95% CIs were estimated for spontaneous abortion and preterm delivery for time-varying exposure. There were 1032 subjects available for analysis; 841 women were exposed to a pH1N1-containing vaccine in pregnancy, and 191 women were unexposed to any influenza vaccine in pregnancy. Nine of 328 (2.7%) first-trimester-exposed pregnancies resulted in an infant with a major birth defect compared to 6/188 (3.2%) in the unexposed (adjusted RR 0.79, 95% CI 0.26-2.42). The HR for spontaneous abortion was not elevated (adjusted HR 0.92, 95% CI 0.31-2.72). Adjusted HRs for preterm delivery were elevated for exposure anytime in pregnancy (3.28, 95% CI 1.25-8.63), specifically with exposure in the 1st or 2nd trimester. However, the mean decrease in gestational age in the exposed pregnancies was approximately three days. Adjusted RRs for small for gestational age infants on weight and length approximated 1.0. For the 2009-12 influenza seasons combined, we found no meaningful evidence of increased RR or HR for major birth defects, spontaneous abortion, or small for gestational age infants. There was some evidence of an increased HR for preterm delivery following pH1N1-influenza vaccine exposure; however the decrease in gestational age on average was approximately three days.
    Vaccine 09/2013; 31(44). DOI:10.1016/j.vaccine.2013.08.097 · 3.62 Impact Factor
Show more