A booster shot is an additional dose of vaccine that provides better protection against the virus.

打加强针是指再打一剂疫苗，以便更好地预防病毒入侵。

For some vaccines, after a while, immunity begins to wear off. At that point, a booster dose is needed to bring immunity levels back up.

有些疫苗，在打过一段时间之后，人体免疫力开始下降。这时候就需要打“加强针”促使免疫水平上调。

What's lesser known about tetanus is that it requires a booster shot every 10 years.

破伤风疫苗每10年需要打一次加强针，这一点很少有人知道。

来源同文世纪翻译，转载请注明出处！