once a one year old receives the measles vaccine ... how...

Question: 

once a one year old receives the measles vaccine ... how long before they are considered protected from the measles virus?

Answer: 

In general, protection starts to develop after about two weeks of getting the measles, mumps, rubella (MMR) vaccine; however, a number of factors impact an individuals’ response to vaccines. 

Two doses of the MMR vaccine are needed for best protection.  The efficacy of a single dose of measles-containing vaccine given at 12 months of age is estimated to be 85% to 95%. With a second dose, efficacy in children approaches 100%.