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Risks and safety of pandemic H1N1 influenza vaccine in pregnancy: birth defects, spontaneous abortion, preterm delivery, and small for gestational age infants.
Vaccine. 2013 Oct 17; 31(44):5026-32.V

Abstract

INTRODUCTION

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.

METHODS

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.

RESULTS

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.

CONCLUSIONS

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.

Authors+Show Affiliations

Department of Pediatrics, University of California San Diego, La Jolla, CA, United States; Rady Children's Hospital, San Diego, CA, United States; Department of Family and Preventive Medicine, University of California San Diego, La Jolla, CA, United States; Clinical Translational Research Institute, University of California San Diego, La Jolla, CA, United States; Vaccines and Medications in Pregnancy Surveillance System, United States. Electronic address: chchambers@ucsd.edu.No affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info available

Pub Type(s)

Journal Article
Research Support, Non-U.S. Gov't
Research Support, U.S. Gov't, P.H.S.

Language

eng

PubMed ID

24016809

Citation

Chambers, Christina D., et al. "Risks and Safety of Pandemic H1N1 Influenza Vaccine in Pregnancy: Birth Defects, Spontaneous Abortion, Preterm Delivery, and Small for Gestational Age Infants." Vaccine, vol. 31, no. 44, 2013, pp. 5026-32.
Chambers CD, Johnson D, Xu R, et al. Risks and safety of pandemic H1N1 influenza vaccine in pregnancy: birth defects, spontaneous abortion, preterm delivery, and small for gestational age infants. Vaccine. 2013;31(44):5026-32.
Chambers, C. D., Johnson, D., Xu, R., Luo, Y., Louik, C., Mitchell, A. A., Schatz, M., & Jones, K. L. (2013). Risks and safety of pandemic H1N1 influenza vaccine in pregnancy: birth defects, spontaneous abortion, preterm delivery, and small for gestational age infants. Vaccine, 31(44), 5026-32. https://doi.org/10.1016/j.vaccine.2013.08.097
Chambers CD, et al. Risks and Safety of Pandemic H1N1 Influenza Vaccine in Pregnancy: Birth Defects, Spontaneous Abortion, Preterm Delivery, and Small for Gestational Age Infants. Vaccine. 2013 Oct 17;31(44):5026-32. PubMed PMID: 24016809.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Risks and safety of pandemic H1N1 influenza vaccine in pregnancy: birth defects, spontaneous abortion, preterm delivery, and small for gestational age infants. AU - Chambers,Christina D, AU - Johnson,Diana, AU - Xu,Ronghui, AU - Luo,Yunjun, AU - Louik,Carol, AU - Mitchell,Allen A, AU - Schatz,Michael, AU - Jones,Kenneth L, AU - ,, Y1 - 2013/09/07/ PY - 2013/06/21/received PY - 2013/08/23/revised PY - 2013/08/27/accepted PY - 2013/9/11/entrez PY - 2013/9/11/pubmed PY - 2014/4/29/medline KW - Birth defects KW - Pandemic H1N1 influenza vaccination KW - Pregnancy KW - Preterm delivery KW - Small for gestational age KW - Spontaneous abortion SP - 5026 EP - 32 JF - Vaccine JO - Vaccine VL - 31 IS - 44 N2 - INTRODUCTION: 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. METHODS: 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. RESULTS: 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. CONCLUSIONS: 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. SN - 1873-2518 UR - https://www.unboundmedicine.com/medline/citation/24016809/Risks_and_safety_of_pandemic_H1N1_influenza_vaccine_in_pregnancy:_birth_defects_spontaneous_abortion_preterm_delivery_and_small_for_gestational_age_infants_ L2 - https://linkinghub.elsevier.com/retrieve/pii/S0264-410X(13)01209-7 DB - PRIME DP - Unbound Medicine ER -