A vaccine is a medicine, usually given by injection, that contains a weakened or dead form of a germ, or just a piece of one. The body meets this harmless version, learns to recognise it, and is then ready to fight the real disease if it ever comes.

A vaccine is a medicine疫苗是一種藥, usually given by injection通常是用注射的方式給予, that contains a weakened or dead form of a germ裡面含有減弱過或已經死掉的病菌, or just a piece of one或只是病菌的一部分。The body meets this harmless version身體遇到這個無害的版本, learns to recognise it學會認出它, and is then ready to fight the real disease if it ever comes然後就準備好在真正的疾病出現時對抗它。

That is the key idea: a vaccine is training, not treatment. It is given to healthy people so they do not get ill later; it does not help someone who is already sick.

That is the key idea這就是關鍵的概念：a vaccine is training, not treatment疫苗是訓練，不是治療。It is given to healthy people它是給健康的人使用的, so they do not get ill later讓他們之後不會生病；it does not help someone who is already sick它沒辦法幫助已經生病的人。

The word is a countable noun — a vaccine, two vaccines, the flu vaccine, a vaccine for children — and it takes both against and for: a vaccine against measles, a vaccine for measles, both fine. In everyday speech people say a shot in America and a jab in Britain, but those words mean the injection; vaccine means the substance inside.

The word is a countable noun這個字是可數名詞 — a vaccine, two vaccines, the flu vaccine, a vaccine for children像a vaccine、two vaccines、流感疫苗、給小孩的疫苗 — and it takes both against and for而且它可以搭against也可以搭for：a vaccine against measles, a vaccine for measles, both finea vaccine against measles跟a vaccine for measles兩種都可以。In everyday speech people say a shot in America and a jab in Britain在日常口語裡美國人說a shot，英國人說a jab, but those words mean the injection但那些字指的是「打針」這個動作；vaccine means the substance insidevaccine指的是裡面的那個物質。

Since 2020 the word has become part of ordinary conversation everywhere, and it now shows up in phrases like vaccine rollout, vaccine hesitancy, and vaccine passport.

Since 2020 the word has become part of ordinary conversation everywhere從2020年起這個字在各地都成了日常對話的一部分, and it now shows up in phrases like vaccine rollout, vaccine hesitancy, and vaccine passport而且現在會出現在像vaccine rollout（疫苗推行）、vaccine hesitancy（疫苗猶豫）、vaccine passport（疫苗護照）這樣的詞組裡。

There is a lovely story inside the spelling. Latin vacca means cow. An English doctor noticed that milkmaids who caught cowpox from cows never got smallpox, and in 1798 he used cowpox to protect people. Every vaccine since — for flu, for polio, for anything — still carries that cow in its name.

There is a lovely story inside the spelling這個字的拼法裡藏著一個很棒的故事。Latin vacca means cow拉丁文vacca的意思是「母牛」。An English doctor noticed一位英國醫生注意到, that milkmaids who caught cowpox from cows never got smallpox從牛身上得到牛痘的擠奶女工從來不會得天花, and in 1798 he used cowpox to protect people於是在1798年他用牛痘來保護人們。Every vaccine since從那之後的每一種疫苗 — for flu, for polio, for anything不管是流感疫苗、小兒麻痺疫苗，還是任何其他疫苗 — still carries that cow in its name名字裡都還帶著那頭牛。