In the UK at the moment there's some controversy regarding the changing of the timing of the Covid vaccination boosters.

All the vaccines I can think of that need boosters are given to babies, whose immune systems aren't fully developed yet. So they get some protection initially but need a booster when they're more mature. Are there any vaccines given to adults that actually need a booster? Was it used in the Covid trials for a good reason, or just to make doubly sure the results would be good? The information I can find online only covers the standard childhood vaccinations, and similar questions on this forum by other people over the past few years have remained unanswered.

  • There a number of adult vaccines that require multiple doses. For example, HAV requires two, HBV and HPV require three. There are other examples. – Carey Gregory Jan 1 at 16:58