Since the start of the pandemic, Éduc’alcool has been regularly reminding Quebecers that heavy drinking can weaken the immune system, particularly when it is trying to fight respiratory diseases, such as pneumonia, tuberculosis or COVID-19.
We have also urged anyone who has COVID-19 not to drink at all until they are fully recovered, so that their immune systems can work at full capacity while fighting the virus.
Now that the vaccination campaign has begun, many questions are being raised about the impact of alcohol on vaccine effectiveness. Here, then, is a review of the potential connections between alcohol and vaccines.
ALCOHOL AND CLINICAL TRIALS
Some clinical trials recruit participants using very strict criteria, such as requiring that participants have no prior health problems or history of heavy drinking. The vaccine developed by AstraZeneca is one example. In such cases, it can be difficult to generalize the results of the trials to a broad population that obviously includes heavy drinkers.
However, Pfizer and Moderna, the companies whose vaccines are currently approved for use in Canada, included drinkers in all phases of their clinical trials. This means that their encouraging results apply to the whole adult population, including drinkers.
VACCINE EFFECTIVE EVEN IN HEAVY DRINKERS
While there are no specific studies examining the impact of drinking on the effectiveness of COVID-19 vaccines, research does show that the immune system’s response to other vaccines is clearly lower among heavy drinkers, particularly those who have a liver disease.
Thus, without the vaccine, heavy drinkers are more at risk for contracting COVID-19 and suffering more serious symptoms.
Also, the COVID-19 vaccine may be less effective among this group of drinkers.
Still, the vaccines currently being administered in Quebec and across Canada can provide additional protection that may counteract the vulnerabilities caused by alcohol among heavy drinkers.
Getting vaccinated against COVID-19 is therefore beneficial for everyone, even heavy drinkers.
BEWARE OF HEAVY DRINKING
Given that heavy drinking can limit the benefits of the vaccine, people who drink to excess should try to get help to stop drinking, or at least to reduce their alcohol intake, while the vaccine’s immunization process is under way.
It is impossible to say exactly how many days before vaccination a person should cut back on their drinking, but clearly, the sooner the better.
Once the second dose of the vaccine has been administered and the immunization process is complete (at least two weeks after the second dose), alcohol intake can be re-evaluated, and who knows? Perhaps recently learned moderate drinking habits can become the new normal.
MODERATE DRINKERS MAY HAVE AN ADVANTAGE
It must be noted that the negative impact of alcohol on immune response does not seem to occur among moderate drinkers. There are even some indications that immune response to vaccines may be stronger among moderate drinkers. However, this does not mean that Éduc’alcool is encouraging people to begin drinking in order to improve their immune response to the coronavirus given that, among other things, the causal link cannot be established. We are simply providing complete information, as always, in keeping with our mission.
Hence, even when it comes to alcohol and the COVID-19 vaccine, moderation is always in good taste.
 Zhang et al. (2008)
 Voysey et al. (2021)
 Polack et al. (2020); Baden et al. (2021)
 Summary of the research presented by Pasala et al. (2015)
 Messaoudi et al. 2013; Roseman et al. (2012)