Covid vaccines, alcohol and marijuana: What to know before your shot - CNBC

"A glass of wine or a beer is OK, but heavy alcohol intake can suppress your immune system and should be avoided in general.

"Certainly when people drink enough to affect their liver, that can affect their immune system," Liu said.

"The liver is a very important organ in terms of having a normal immune response, and people who have poor liver function for various reasons may not respond well to the vaccine and in general are probably at a higher risk of complication from Covid," she said.

"What is not necessarily the case with other respiratory viruses and has clearly been the case with Covid is that people with disorders of blood vessels and the cardiovascular system are at much higher risk of complications with Covid, which is why smokers were high priority in some places for getting the vaccine," she said.

Consuming marijuana in ways other than smoking is probably fine: "While there aren't any studies on the effect of marijuana and Covid vaccine, it is unlikely to affect the immune response to vaccine," Yang said.