@overholt This is a really important PSA! When I was getting ready to go to college in the late '80s they were systematically requiring a re-up of the measles vaccination due to the exact concern you mention. As a know it all teenager at the time, I was annoyed. But in the last several years, I've been grateful for that proactive requirement - made by the US Naval Hospital in Bethesda MD, which has since been merged with Walther Reed Army Medical Center.