@NJoIdaR @TrumpUndead @jonathanchait Flu has a distinct season of about 4 months. That's all the protection you need because there is no flu circulating outside that time. The influenza vaccine doesn't protect much longer than that, if even that long.
@NJoIdaR @TrumpUndead @jonathanchait 流感有一个独特的季节，大约有 4 个月。这就是您需要的所有保护措施，因为在那段时间之外没有流感流行。流感疫苗的保护时间不会超过这个时间，即使是那么长。