Vaccine
PREGNANCY RECOMMENDATION: Compatible (Inactivated Vaccine) No Human Data—Probably Compatible (Live Virus Vaccine and Adjuvanted Vaccine)
BREASTFEEDING RECOMMENDATION: Compatible
PREGNANCY SUMMARY
Because the H1N1 vaccines were released late in 2009, there are no reports describing their use in pregnancy. However, pregnant women are a priority population to receive the inactivated H1N1 vaccine because they are at high risk for morbidity and mortality. There is no evidence that influenza virus types A and B vaccines caused embryo or fetal harm (see Vaccine, Influenza). There is, however, a possible increased rate of spontaneous abortions from disease caused by these viruses (1). Inactivated virus vaccines are preferred over vaccines containing live viruses. The American College of Obstetricians and Gynecologists classifies live virus vaccines as usually contraindicated (1). The potential for developmental toxicity from the adjuvants, added to one of the H1N1 vaccines to enhance the immune response to the antigen (i.e., the virus), is not known. In rats, however, developmental toxicity was observed in two studies with AS03-adjuvanted H5N1 antigen. Neither of the vaccines available in the United States contains an adjuvant. If H1N1 vaccine is used in pregnancy, health care professionals are encouraged to call the toll-free number 877-311-8972 for information about patient enrollment in the Organization of Teratology Information Specialists (OTIS) study.
FETAL RISK SUMMARY
Three vaccines, two with inactivated virus and one with live virus, are available to prevent infection with novel influenza A (H1N1) (previously known as swine flu). The vaccines are indicated for the active immunization against influenza disease caused by pandemic (H1N1) 2009 virus (2–4). Influenza A (H1N1) 2009 monovalent vaccine, given by IM injection, is an inactivated vaccine indicated for persons 6 months of age and older (2). Influenza A (H1N1) 2009 monovalent vaccine live, given intranasally, is indicated for individuals 2–49 years of age (3). Arepanrix H1N1 inactivated virus vaccine, available in Canada, is indicated in an officially declared pandemic situation (4). The adjuvants in Arepanrix are DL-α-tocopherol, squalene, and polysorbate 80.
Animal reproduction studies with H1N1 vaccines have not been conducted (2–4). Neither have studies been conducted for carcinogenesis, mutagenesis, or impairment of fertility. Two reproductive studies in rats with AS03-adjuvanted H5N1 antigen (doses not specified) have been conducted to evaluate the embryo–fetal and postnatal toxicity up to the end of the lactation period (4). The findings in the two studies were an increased incidence of postimplantation loss, fetal malformations (markedly medially thickened/kinked ribs and bent scapula), dilated ureter, and delayed neurobehavioral maturation. However, the significance of the outcomes was uncertain because not all findings were observed in both studies (4).
BREASTFEEDING SUMMARY
Because the H1N1 vaccines were released late in 2009, there are no reports describing their use during breastfeeding. Nevertheless, maternal vaccination with any of these vaccines is compatible with breastfeeding and presents no risk to a nursing infant.
References
1.American College of Obstetricians and Gynecologists. Influenza vaccination during pregnancy. Committee Opinion. No. 468, October 2010. Obstet Gynecol 2010;116:1006–7.
2.Product information. Influenza A (H1N1) 2009 Monovalent Vaccine. Sanofi Pasteur, 2009.
3.Product information. Influenza A (H1N1) 2009 Monovalent Vaccine Live, Intranasal. MedImmune, 2009.
4.Product information. Arepanrix H1N1 AS03-Adjuvanted H1N1 Pandemic Influenza Vaccine. GlaxoSmithKline, 2009.