* First, EUA was for a two-shot regimen. * Then, a booster after 8 months was proposed[1]. * Then, booster date was moved to 6 months[2] after second shot. *

* First, EUA was for a two-shot regimen. * Then, a booster after 8 months was proposed[1]. * Then, booster date was moved to 6 months[2] after second shot. * Then, the interval between second shot and booster shot goes down to 5 months[2]. First shot is followed by three weeks of reduced immunity. It takes two weeks after the second shot, one is considered fully vaccinated. That means, one gets to be in "fully vaccinated" status for a mere 4.5 months. So, it took a week to go from eight months to six months, but only a day to go from 6 months to 5 months. [1]: https://www.whitehouse.gov/briefing-room/statements-releases/2021/08/18/fact-sheet-president-biden-to-announce-new-actions-to-protect-americans-from-covid-19-and-help-state-and-local-leaders-fight-the-virus/ https://www.whitehouse.gov/briefing-room/statements-releases... [2]: https://www.wsj.com/articles/biden-administration-plans-covid-19-vaccine-boosters-at-six-months-instead-of-eight-11629919356 https://www.wsj.com/articles/biden-administration-plans-covi...