2. A few days after vaccination in COVID-19: One to two weeks is recommended. Although under normal circumstances, normal diet and activities will not affect the effect of the vaccine, some people may have some uncomfortable reactions after being vaccinated with COVID-19 vaccine due to personal physical differences. For this kind of people, it is suggested that it is best not to eat for a week or two, and then slowly return to normal diet after feeling normal, so as to reduce discomfort or illness caused by other reasons to some extent.