Yellow fever vaccine virus transmitted via breast-feeding

Physicians should avoid vaccinating women who are breast-feeding against yellow fever whenever possible after reports last week indicated that a breast-fed, 23-day-old infant developed symptoms and tested positive for 17DD yellow fever virus after her mother was administered the yellow fever vaccine.

In April 2009, a 22-year-old mother who gave birth to a healthy female infant was administered the 17DD yellow fever vaccine during a postpartum visit to her health care provider due to an epidemic spreading through Rio Grande do Sul, Brazil, where she resided.

Eight days after vaccination, the infant was hospitalized with a suspected diagnosis of meningoencephalitis after exhibiting fever, irritability, refusal to nurse and continuous seizure activity requiring IV diazepam, according to the researchers. Perioral cyanosis was also observed.

The researchers noted that lab exam and a Gram’s stain of cerebrospinal fluid appeared unremarkable and indicated no bacteria. However, the infant was assigned to oxygen therapy, IV dipyrone and phenytoin along with empiric treatment for bacterial infection with ampicillin and gentamicin. Empiric acyclovir was eventually added.

The researchers reported that bacterial and fungal cultures were not taken, but serum and CSF samples were tested for dengue-specific immunoglobulin M. Viral cultures were also tested for herpes simplex, cytomegalovirus and varicella whereas reverse transcription polymerase chain reaction was used to screen for enteroviruses. All tests were negative, according to the researchers. However, increased frequency of convulsions and persistent perioral cyanosis prompted the infant’s transfer to the pediatric ICU.

After a second CSF examination, the mother told physicians that she had been administered yellow fever vaccine eight days prior to the appearance of symptoms. A serum and CSF sample from the infant revealed yellow fever–specific IgM antibodies. Yellow fever viral RNA was amplified by RT-PCR, revealing an identical nucleotide sequence to 17DD yellow fever vaccine virus. The Brazilian Committee on Vaccine-Associated Adverse Events classified the infant’s encephalitis as yellow fever vaccine–associated neurologic disease.

The infant recovered and was discharged from the hospital on May 10, 2009. Follow-up described the infant as demonstrating normal neurodevelopment and growth at 6 months old, the researchers wrote.

“The findings in this report provide documentation that yellow fever vaccine virus can be transmitted via breast-feeding. Administration of yellow fever vaccine to breast-feeding women should be avoided except in situations where exposure to yellow fever viruses cannot be avoided or postponed,” the researchers wrote. – by Melissa Foster

Couto AM. MMWR. 2010;59:130-132.

This MMWR article documents maternal-to-infant transmission of yellow fever virus presumably through breast milk. The virus is a live virus vaccine with the potential to cause meningoencephalitis in infants aged younger than 6 months and in the elderly. Although this is the first well-documented case of this occurring through breast milk and although use of yellow fever vaccine is uncommon in the United States, the case serves as a reminder that the vaccine should not be given to infants aged younger than 6 months or to breast-feeding mothers unless the threat of wild-type yellow fever is eminent.

– Steven B. Black, MD
Infectious Diseases in Children Editorial Board

The report of vaccine-associated yellow fever in an infant acquired through breast feeding is an excellent example of the importance of assessing potential adverse events associated with vaccines. The investigators did a comprehensive job of evaluating the child, carefully measuring the immunologic responses and viral detection in the CSF and providing guidance to others on the risk associated with administration of this live-attenuated vaccine in nursing mothers. This report is a valuable addition to the literature and a model for those of us evaluating the safety of vaccines.

– Kathryn M. Edwards, MD
Infectious Diseases in Children Editorial Board

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