Children should be vaccinated after their first birthday and receive an additional dose of MMR vaccine before entering kindergarten (when they’re 4 to 6 years old). The second dose provides additional protection to the approximately 5% of people who do not respond to their first dose of the vaccine. Given the risk of measles associated with international travel, a first dose can be given as early as 6 months of age. This does not, however, negate the need for additional MMR doses administered at the traditional timepoints of over 1 year of age and around 4 to 6 years of age.