Subacute sclerosing panencephalitis — a 100% fatal complication of measles — occurs much more often than previously thought, according to data presented at IDWeek 2016. The recent finding underscores the importance of herd immunity with the measles-mumps-rubella vaccine to protect infants and those who are immunocompromised.

The MMR vaccine is not recommended in infants aged younger than 12 months because they retain maternal antibodies that would make the vaccine less effective; however, this population is still at risk for contracting measles. Infants who are infected with the virus are predisposed to subacute sclerosing panencephalitis (SSPE), a deadly neurological condition that occurs when the measles virus spreads to the brain. The virus can lay dormant for years before eventually causing SSPE. Questions on what causes the virus to reactive remain unanswered.