副反応(ふくはんのう)

ふくはんのう
noun
side effect (esp. of a vaccine)
1. side effect; adverse reaction (esp. to a vaccine)
An unintended bodily reaction to a vaccine. Distinguished in Japanese medical usage from 副作用(ふくさよう), which is reserved for side effects of medications. The term became widely known during the COVID-19 vaccination campaign.
副反応(ふくはんのう)で熱(ねつ)が出(で)た。
I got a fever as a side effect.
ワクチンの副反応(ふくはんのう)は個人差(こじんさ)が大(おお)きい。
Vaccine side effects vary greatly from person to person.
副反応(ふくはんのう)が心配(しんぱい)な方(かた)は医師(いし)に相談(そうだん)してください。
Those concerned about side effects should consult a doctor.

Compound of 副(ふく) (sub-, secondary) + 反応(はんのう) (reaction). In Japanese medical terminology, this word is used specifically for vaccines, distinguishing it from drug side effects.

COMMON COLLOCATIONS:

  • 副反応(ふくはんのう)が出(で)る: to develop a side effect
  • ワクチンの副反応(ふくはんのう): vaccine side effect
  • 副反応(ふくはんのう)報告(ほうこく): side-effect report
  • 重(おも)い副反応(ふくはんのう): serious side effect

SIMILAR WORDS:

  • 副作用(ふくさよう): side effect (of medication) — for drugs, not vaccines
  • 有害事象(ゆうがいじしょう): adverse event — broader medical term covering any unfavorable occurrence
general
Added 2026.6.5 13:08
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