Reported February 12, 2010

A breastfed baby contracted the yellow fever vaccine virus in Brazil a week after its mother was immunised against the disease, report health officials today in the Morbidity and Mortality Weekly Report. The case is the first of its kind to be confirmed anywhere in the world.

“[Y]ellow fever vaccine virus can be transmitted via breast feeding,” write the US Centers for Disease Control and Prevention (CDC). “Administration of yellow fever vaccine to breast-feeding mothers should be avoided.”

The jab should still be given to nursing mothers who cannot avoid travelling to areas where the virus circulates, adds the CDC.

Yellow fever vaccination guidelines issued by the World Health Organization do not currently make recommendations for breastfeeding mothers. Brazilian health authorities currently caution against giving them the jab, but are now revising these guidelines as a result of the investigation. It is not clear from today’s report whether they will make any new recommendations for use of the vaccine.

In the case described today, a mother was vaccinated against yellow fever after the disease broke out in her town. She lived in a region of Rio Grande do Sul state usually unaffected by the mosquito-borne disease. Two days after receiving the jab she felt tired, had a headache and a fever but did not seek medical help for her symptoms, according to the report.

Within a week of getting the jab, her three-week old baby, who had been fed only breast milk, was admitted to hospital with seizures and was diagnosed with meningoencephalitis — a medical condition where the brain and meninges become infected. Tests revealed traces of the yellow fever vaccine virus in the child’s blood.

The researchers did not take samples of breast milk from the mother to test for the yellow fever virus. But they say the evidence suggests this is the first confirmed case of mother-to-child transmission of yellow fever vaccine virus through breast milk. In 2009, the CDC learned of a child in Canada who developed neurological disease after coming into contact with the vaccine virus in breast milk, but immunisation was not confirmed as the cause in that case.

Yellow fever vaccine is not recommended for children under six months of age because the risk of neurological disease as a result of the immunisation is deemed too high.

Source : Emerging Health Threats