A single case report has raised concern that yellow fever vaccine virus may be transmitted through breast milk, suggesting the need to avoid administering the vaccine to breastfeeding women.
The case involved a 22-year-old Brazilian woman who virus to her 3-week-old baby through her breast milk.
The mother, who lived in area that was fighting an outbreak of yellow fever, received the 17DD yellow fever vaccine about two weeks after giving birth to a healthy baby, according to Aline Mallmann Couto, MD, of the Hospital de Caridade de Cachoeira do Sul in Brazil, and colleagues.
Five days after receiving the vaccine, the mother developed a headache, malaise, and a low fever, which persisted for two days, the researchers reported in the Feb. 12 issue of Morbidity and Mortality Weekly Report.
A day after her symptoms resolved, the baby, who was exclusively breastfed, developed fever and irritability, and was eventually admitted to the hospital with seizures. The infant received antimicrobial and antiviral treatment for meningoencephalitis and was discharged fully recovered after 24 days.
Yellow fever-specific immunoglobulin M antibodies were detected in the baby's cerebrospinal fluid and serum, indicating a nervous system infection. Neither breast milk nor maternal serum were tested for yellow fever virus.
The Brazilian Committee on Vaccine-Associated Adverse Events classified the infant's encephalitis as yellow fever vaccine-associated neurologic disease.
According to an editorial note accompanying the report, this is the first laboratory-confirmed case of yellow fever vaccine virus being transmitted to a nursing infant through breast milk.
The Brazilian Ministry of Health has revised its recommendations regarding the administration of yellow fever vaccine to breastfeeding women, saying that it should be avoided except when exposure to the virus cannot be avoided or travel cannot be postponed.
In 2002, the CDC's Advisory Committee on Immunization Practices (ACIP), which recommends vaccination for all people living in or traveling to areas where the virus is endemic, issued similar guidance based on the theoretical risk of transmitting yellow fever vaccine virus through breast milk.
Yellow fever is endemic in much of northern South America and central Africa. A live, attenuated vaccine is made from various strains of the 17D yellow fever virus lineage.
According to the MMWR editors, there are about 0.4 cases of neurologic disease resulting from vaccination per 100,000 people who are immunized. However, the rate is much higher in infants 6 months and younger -- 0.5 to 4.0 cases per 1,000. Vaccination is contraindicated in this age group.
Primary Source
Morbidity and Mortality Weekly Report
Mallman Couto A, et al "Transmission of yellow fever vaccine virus through breastfeeding -- Brazil, 2009" MMWR 2010; 59: 130-132.