The CDC recommends children get two doses of the MMR (measles, mumps, and rubella) vaccine.
The first dose is recommended between 12 and 15 months old. The second dose is recommended between 4 and 6 years of age. Children may receive the second dose earlier than this, though, as long as it's given at least 28 days after the first dose.
There's also another rubella vaccine option for children ages 1 to 12 that includes varicella (chickenpox) vaccine. This vaccine is called the MMRV vaccine — measles, mumps, rubella, and varicella (chickenpox).
The CDC recommends two doses, with the first at age 12–15 months and the second at age 4–6 years old.