Global Vaccine Safety

Yellow fever vaccine and breastfeeding

Extract from report of GACVS meeting of 16-17 June 2010, published in the WHO Weekly Epidemiological Record on 23 July 2010

The Committee reviewed recent data suggesting that 3 neonates (aged 10 days, 23 days and 5 weeks) developed encephalitis as a result of infection with yellow fever vaccine virus transmitted to them from their recently-vaccinated mothers. All 3 infants were being breastfed, but the mode of transmission has not been established. All 3 mothers had received the vaccine for the first time during the infant’s first month of life. Further research is needed to quantify the potential risk of transmission of yellow fever vaccine virus from mothers to infants, including the possibility of transmission through breastmilk.

Mass vaccination campaigns being conducted in West Africa provide an opportunity to conduct studies that will clarify these issues. Such studies might test breastmilk from vaccinated mothers for the presence of vaccine virus, and test infants for evidence of seroconversion to the vaccine virus. The potential risk of transmission may vary depending on whether mothers are vaccinated for the first time or have been previously vaccinated.

In areas where yellow fever is endemic, or during outbreaks, the Committee believes that the benefits of vaccinating nursing mothers are likely to far outweigh the risk of potential transmission of vaccine virus to infants; the Committee also believes that the benefits of breastfeeding far outweigh the alternatives for infant feeding. Nursing mothers who are considering travel to endemic areas should be counselled regarding the benefits and potential risks of vaccination. Vaccination is recommended if vaccination is indicated for a breastfeeding woman and travel cannot be avoided or postponed.