Unlike a lot of pathogenic diseases, measles requires an extraordinarily high amount of herd immunity (upwards of 95%), so this isn't a particularly telling data point on its own.
RFK Jr has been pushing anti-vaccine bullshit for decades. He was already taking defensive stances on his activism (Oh, I'm not anti-vaccine, I'm just providing nonsense arguments and clout for anti-vaccine stances) back in 2015.
Kennedy was already pushing bullshit during the UK Measles vaccine fraud/scare, back in 2005. He was doing this along with a few other celebrities.
I've responded to a few people on this but the comment I was responding to was literally about the last 6 years! The context of this entire thread is about MAGA / Trump! I agree that RFK is hurting and has been for a long time, but that is not what this argument is about!