Vaccine, Smallpox in Pregnancy and Breastfeeding

Risk Factor: X
Class: Serums, toxoids, and vaccines / Vaccines

Contents of this page:
Fetal Risk Summary
Breast Feeding Summary
Questions and Answers

Fetal Risk Summary

Smallpox vaccine is a live, attenuated virus vaccine (1,2). Although smallpox infection had a high mortality rate, the disease has been largely eradicated from the world (1,3). Vaccination during pregnancy between 3 and 24 weeks has resulted in fetal death (2,3). A 1974 Reference reviewed the published reports of smallpox vaccination during pregnancy and found 20 cases of fetal vaccinia among more than 8,500 maternal vaccinations (4). Of the 21 exposed fetuses (1 set of twins), only 3 of the 10 liveborns survived. There was only weak evidence, however, that vaccination during the 1st trimester increased fetal wastage compared with that occurring later in gestation (4).

Although the incidence of fetal vaccinia with subsequent poor outcome resulting from maternal vaccination appears to be rare, most sources consider smallpox vaccine to be contraindicated during pregnancy (1,2 and 3,5).

Breast Feeding Summary

No data are available.


  1. Amstey MS. Vaccination in pregnancy. Clin Obstet Gynaecol 1983;10:1322.
  2. American Hospital Formulary Service. Drug Information 1997. Bethesda, MD: American Society of Health-System Pharmacists, 1997:26469.
  3. Hart RJC. Immunization. Clin Obstet Gynaecol 1981;8:42130.
  4. Levine MM. Live-virus vaccines in pregnancy. Risks and recommendations. Lancet 1974;2:348.
  5. Linder N, Ohel G. In utero vaccination. Clin Perinatol 1994;21:66374.

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