the pfizer authorization is based on 4 months of data (https://blogs.bmj.com/bmj/2021/08/23/does-the-fda-think-these-data-justify-the-first-full-approval-of-a-c

the pfizer authorization is based on 4 months of data (https://blogs.bmj.com/bmj/2021/08/23/does-the-fda-think-these-data-justify-the-first-full-approval-of-a-covid-19-vaccine/ https://blogs.bmj.com/bmj/2021/08/23/does-the-fda-think-thes...) your 2nd measles vaccine had 25 years of data since your last one, they probably had enough time to know that it would be fine