5yr old had mmr vaccine when he was 1. blood teiter test shows immunity does he still need a booster shot, if yes then when and how long its good for?

MMR revaccination: We now give a second MMR at age five or six. There have been failures in the measles and mumps components. Therefore a second and final MMR is recommended at school age.

Boosting immunity: We gave one MMR for about 22 years before realizing that enough kids had lost some of their protection that they were getting measles as college freshman. The addition of the 2nd dose at 5, regardless of their blood test at that age, has essentially eliminated seasonal outbreaks of measles on collage campuses. It may be another two decades before we know if other boosters are needed later.