prophylactic drug; preventive medicine
Refers to a medicine taken to prevent disease, such as a vaccine or a prophylactic pill.
I took malaria prophylactic medicine before traveling.
This preventive medicine is effective in preventing influenza infection.
ワクチン specifically refers to a vaccine, a type of 予防薬 that stimulates immunity.
Compound of 予防 (よぼう, 'prevention') and 薬 (やく, 'medicine').