MMR Vaccine: When Is the Right Time for the Second Dose?

Outbreaks of measles have been reported over the past 5 years, particularly affecting children between the ages of 1 and 5 years. Most of these children are younger than the age recommended by the Advisory Committee on Immunization Practices for the second dose of measles-mumps-rubella (MMR) vaccine. Question may arise as to whether strict adherence to the scheduled second dose is required or whether there is opportunity for earlier immunization under special circumstances (e.g., traveling abroad, poor response as evidenced by titer levels). The history of measles, its characteristics, and its evolving past and current immunization policies will be reviewed, focusing on the original intent of the recommended schedule and presenting a case in which deviating from current practice could be justified.