It's quite possible that if measles were introduced to our global population now it would be exactly the same: has so much spread that it has the chance to muta

It's quite possible that if measles were introduced to our global population now it would be exactly the same: has so much spread that it has the chance to mutate to evade the immune system next time around. If 99% of people were vaccinated then covid wouldn't have populations in which to mutate.