At which ages should children receive their first measles, mumps, and rubella (MMR) vaccine?

The correct answer is based on the recommended immunization schedule established by health authorities. Children should receive their first dose of the measles, mumps, and rubella (MMR) vaccine between the ages of 12 to 15 months. This timing is crucial as it ensures that the child's immune system is developed enough to respond effectively to the vaccine, thereby providing immunity against these diseases.

The second dose is recommended between the ages of 4 to 6 years. Administering the vaccine at this age not only helps to boost the immune response but also coincides with other vaccinations needed before starting school. By following this schedule, the vaccination program aims to achieve optimal immunity in the population and prevent outbreaks of these infectious diseases.

Other options do not align with the established vaccination schedule. Suggestions for vaccination at ages that fall outside the recommended timeline, such as administering the MMR vaccine too early or inappropriately spaced, can lead to suboptimal immunity and increase the risk of measles, mumps, or rubella outbreaks.