@ScottB99329729 @benny171a @TrumpUndead @jonathanchait There are multiple motivations for boosters but the main one was that the original schedule just wasn't very good. It was the first thing tried that worked at all, but without going through multiple iterations. It probably should have always been a 3 dose series.
@ScottB99329729 @benny171a @TrumpUndead @jonathanchait 助推器有多种动机，但主要的动机是最初的时间表不是很好。这是第一个尝试的东西，它完全有效，但没有经过多次迭代。它可能应该一直是一个 3 剂量系列。