Otsuka Seiyaku, one of Japan’s leading pharmaceutical companies, published an article on how to boost immune system on its website. While there are several ways, one of them is to consume green tea components. A study on 200 subjects shows that one group who was given green tea components (378 mg catechin and 210 mg theanine per day) were significantly less susceptible to influenza in contrast to another group who received placebo!
The other ways to boost immune system in the article include: to laugh, to stay warm, to stay positive, to exercise moderately, and to have a balanced diet.
Please stay healthy and safe! Wash your hands, and drink lots of green tea!
どうぞお元気で！

How to Boost Immune System (Japanese)