The U.S. Centers for Disease Control and Prevention's Advisory Committee on Immunization Practices recommends that American children receive the rotavirus vaccine at 2, 4 and 6 months of age.
But before the WHO's Strategic Advisory Group of Experts on Immunization would recommend vaccinating children in developing nations, it wanted to see research that showed the vaccines would be effective in poorer nations, Neuzil said.
Both of the rotavirus vaccines available are live oral vaccine. Prior research on other live oral vaccines, including polio and cholera, has shown they don't work as well among very low-income populations. The reasons are unclear, but some suspect poorer nutrition or higher rates of the disease in those countries mean that children may already have some antibodies to the virus, perhaps through breast milk, so the vaccine may not fully "take," Neuzil said.
Prior to publication of the new studies, the results were shared with WHO, which has since recommended the rotavirus vaccine for infants in developing nations, with the first dose being given between 6 and 15 weeks of age.
The WHO's recommendation is critical, Neuzil said, not only for influencing health-policy decisions, but for starting the flow of aid and philanthropic dollars to pay for rotavirus vaccination programs.
In the study in Africa, researchers divided nearly 5,000 infants from Malawi and South Africa into three groups: one-third received three doses of the vaccine, one-third received two doses and one-third received a placebo. Researchers then followed-up with weekly home visits and took stool samples to confirm suspected rotavirus infections.
Children who had received either the three-dose or the two-dose regimen were 61 percent less likely to develop severe rotavirus infection. In Malawi, the effect
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