A study conducted in Zambia show that measles poses a greater fatality risk in HIV-infected children than in uninfected children and hence there is a need of re vaccination of these children. Measles antibody levels in HIV-infected children rapidly diminish following vaccination, emphasizing the importance of supplementary vaccinations to maintain immunity.
Measles is a highly contagious disease. It has killed more than 450,000 people in 2004, according to the U.S. Centers for Disease Control. More than half of those deaths were in sub-Saharan Africa, a region also hard hit by HIV and AIDS.
William Moss is an epidemiologist at the Johns Hopkins Bloomberg School of Public Health. He and his colleagues have been studying the effectiveness of measles vaccines given to children in Lusaka, Zambia. In their study, 441 children were vaccinated, including 66 who were infected with HIV.
Measles vaccine was administered in both groups at age 9 months. Children were followed for up to 27 months thereafter. Some received repeat vaccination. Measles-specific antibodies in the blood were then measured on subsequent visits.
Dr. Moss and colleagues found that although 88 percent (44 of 50) of HIV-infected children developed protective antibody levels within 6 months of vaccination, during 27 months of follow-up , only half of the  HIV-infected children who survived maintained protective antibody levels, compared with almost 90 percent [63 of 71] of the HIV-uninfected children." In contrast, 92 percent (11 of 12) of HIV-infected children who were vaccinated a second time during follow-up had protective antibody levels.
These results suggest that "in the short term, re-vaccination was able to protect these children," says Moss.
According to Moss, "Because measles virus needs only a small proportion of susceptible children to sustain transmission and cause outbreaks, these vaccinated but susceptible HIV-infected children could impede measles elimination efforts in regions of high HIV prevalence."
The World Health Organization recommends that all children be vaccinated twice to protect them from measles infection. Moss's research indicates that repeated vaccinations may be especially critical in countries with high rates of HIV-infection.