This is the 3063rd most frequent Japanese word.
ワクチン
Vaccine.
The word 『ワクチン』 is used here as the subject in relation to health prevention measures.
ワクチンを受けることは病気を予防する方法です。
Receiving a vaccine is a way to prevent illnesses.
In this sentence, 『ワクチン』 is used to refer to an action of vaccination taken before travel.
旅行の前にワクチンを打つことを勧められます。
It is recommended to get vaccinated before traveling.
Here, 『ワクチン』 is used in the context of scientific research concerning its effectiveness.