MONTREAL -- Alcohol consumption could have an impact on the effectiveness of the COVID-19 vaccine, but there is currently no data available to confirm this.

In a news release issued earlier this week, the organization Éduc'Alcool said that the benefits of vaccination may be "diminished" in excessive drinkers.

However, the immune response "could be even better" in moderate drinkers, the organization continues.

"Are there any firm studies that say this is certain to have an effect on the vaccine? No," said Dr. Julie Bruneau, a CHUM addiction expert who recently became a member of Éduc'Alcool's scientific council.

"No one knows. Maybe if we drink a lot, our vaccine will work, and maybe if we don't drink, it won't work. On an individual level, we don't know."

It can be assumed that heavy drinking would have different effects on the immune system and previous observational studies have shown that heavy drinkers don't respond as well to known vaccines, such as the Hepatitis B vaccine.

However, it is impossible to say whether this diminished response is due to alcohol consumption, other lifestyle components or even other health problems from which drinkers may suffer. All of these elements are inseparable, said Bruneau.

The same is true for moderate drinkers who have been found to have a beneficial immune response.

"Women who drank one glass of alcohol and men who drank two had all kinds of responses that appeared to be good immune system responses," Bruneau said. "But it's always annoying, because when we talk about people who drink very little or who don't drink, we get into all kinds of socio-economic considerations that can also have a big influence on general health and immunity."

Éduc'Alcool specifies that the goal is obviously not to encourage Quebecers to start drinking to improve their immune response to the coronavirus.

Nor can the results obtained with other vaccines automatically be transposed to the coronavirus vaccine, which is based on new technology and fights a different virus.

"You have to be careful," Bruneau added. "There is no correlation between behaviour, a glass of alcohol, and the effectiveness of a vaccine that we know little about."

That being said, she continued, "it makes all the sense in the world to tell people, 'don't consume a large quantity of alcohol before you go to get vaccinated,'"

Right now, the best strategy is to rely on what seems most likely and to rely on the available data.

"What is known about old vaccines leads us to be cautious and to say that perhaps people who drink a lot of alcohol are at risk of responding less well, especially if they drink a lot on a regular basis," Bruneau concluded.

"Heavy drinking is definitely not a good idea before getting vaccinated. It's not a good idea, period."

-- this report by The Canadian Press was first published Jan. 29, 2021.