"CDC considers people who received two doses of measles vaccine as children according to the U.S. vaccination schedule protected for life, and they do not ever need a booster dose," according to the CDC.
https://www.newsweek.com/measles-immunization-vaccine-immune-schedule-1403860
And yet the measles vaccine failure rate for 2 doses is around 50%.
https://www.nvic.org/vaccines-and-diseases/Measles/measles-vaccine-effectiveness.aspx
And in fact many of the outbreaks are among the fully vaccinated.