Up to half of children infected with HIV at birth don’t have the necessary immunity to ward off measles, mumps, and rubella, according to new research.Infectious disease experts say this is a result of years of cautious immunization practices in young HIV patients.

It can, however, be corrected by ensuring that children with HIV have their full course of measles, mumps, and rubella (MMR) vaccinations.

The research, conducted by the National Institutes of Health (NIH) and the U.S. Centers for Disease Control and Prevention (CDC), involved 600 children exposed to HIV in the womb.