Youths who contracted HIV at birth may lack immunity to measles, mumps and rubella (MMR) despite vaccination for the three diseases, Slate reports. Publishing their findings in Clinical Infectious Diseases, researchers studied 669 children ages 7 to 15 between 2007 and 2009. Of these children, 428 contracted HIV around the time of birth, while the others were born to HIV-positive mothers but did not ultimately contract the virus. The participants were recruited from the Pediatric HIV/AIDS Cohort Study.

About 93 percent of the children had received at least the recommended two doses of the MMR vaccine. The recommended dosing schedule is one shot at 12 to 15 months of age and another when a child is 4 to 6 years old.

Many of the children who contracted HIV at birth were born before 1996, when the modern era of combination ARV treatment began.

The HIV-positive children were much less likely than the HIV-negative children to have protective antibodies against measles, mumps and rubella. However, the HIV-positive children who began ARVs before receiving their MMR shots were more likely than the other children with HIV to have protective levels of antibodies for the three vaccine-preventable diseases, in particular if their CD4 cells were higher at the time of the vaccinations.