From: Effect of gargling with tea and ingredients of tea on the prevention of influenza infection: a meta-analysis
Newcastle-Ottawa scale
Study
Iwata et al. 1997
Yamada et al. 2006
Criterion
[17]
[18]
Selection (range, 0–4 stars)
***
Comparability (range, 0–2 stars)
*
Outcome (range, 0–3 stars)
