Which statement about the MMR vaccine is correct?

The correct choice identifies that two doses of the MMR (measles, mumps, and rubella) vaccine are given at specific ages: typically, the first dose is administered at 12 months, followed by a second dose at 4 years of age. This schedule is part of the recommended immunization practices to ensure that children build adequate immunity against these viral infections.

The first dose at 12 months is important as it provides early protection during a vulnerable development stage. The second dose at 4 years boosts the immune response, reinforcing and ensuring long-lasting protection against these illnesses, which can lead to serious complications if contracted. This schedule is well-established in pediatric immunization guidelines to optimize immune response and community health.