I found an interesting article that describes the first laboratory-confirmed case of the Yellow Fever vaccine being transmitted through breast milk. The infant is also the youngest reported case of yellow fever associated neurological disease (YEL-AND). The mother was vaccinated shortly after giving birth when a yellow fever (YFV) epidemic spread to the mother's home town in Brazil, which was a nonendemic area. Five days later the mother developed a low fever, headache, and malaise (all normal side effects of the vaccine); three days later the infant started showing symptoms including fever, arability, and seizure-like activity. The infant was admitted to the hospital for meningoencephalitis. YFV was confirmed by type-specific antibodies in the serum and CSF; virus was also detected in the CSF by RT-PCR. The sequence that was found by RT-PCR was identical to the 17DD yellow fever vaccine virus; the vaccine is live, attenuated. The infant recovered without any long-term neurological damage.
YEL-AND has been reported in children under six months old occurring at a rate of 50-400 cases per 100,000 vaccinated. Vaccination of children under six months old is not recommended by the CDC because of the increased risk of YEL-AND. The advisory committee on immunization practices also discourages vaccinating breast-feeding mothers to avoid possible transmission to the infant, as seen in this case.
The detection of YFV in breast milk has not been seen before, although West Nile Virus (WNV), another flavivirus, has been detected in breast milk before. There is one probable case of WNV transmission through breast milk. Both YFV and WNV are normally transmitted by container breeding mosquitoes. I think that it is interesting that there is evidence of another mode of transmission for these two viruses. It would be interesting to see if other flaviviruses such as Dengue, Japanese Encephalitis, and St. Louis Encephalitis can be detected in breast milk as well.
"Transmission of Yellow Fever Vaccine Virus Through Breast-Feeding---Brazil,2009." Morbidity and Mortality Weekly Report. 12 Feb. 2010
Wow, that is fascinating and scary. I'm glad the child was eventually OK. I think we mentioned in class that there have been several hundred observations of pregnant mothers getting MMR (also live vaccines) without any harm to the fetus. I'd guess that MMR would not be harmful is a breast-feeding mom got it, but under normal circumstances, why would she?
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