Early MMR vaccination during measles outbreaks: Reconsidering routine timing.

Measles cases are increasing across the United States, with infants under age 12 months at increased risk as they are not yet eligible for routine measles, mumps, and rubella (MMR) vaccination. The current MMR vaccination schedule is based on decades-old data from an era of widespread natural maternal immunity and low measles prevalence. Today, most mothers have vaccine-derived immunity, and recent studies show these maternal antibodies wane by 3 to 6 months of age, leaving many infants vulnerable to infection until they receive their first MMR vaccine at the currently recommended age of 12 to 15 months. Evidence demonstrates, however, that MMR vaccination between ages 6 and 11 months provides partial protection during outbreaks and does not impair the immune response to later doses. Safety data also support vaccination in younger infants. Although early MMR vaccination is currently recommended before international travel, it should also be offered domestically during outbreaks as a risk-based strategy. National guidance should be updated to reflect current epidemiology and close this gap in infant protection.