Doctors have long known that excessive alcohol consumption — more than four drinks on a given day for men or more than three for women — can do a number on the immune system. Not only do heavy drinkers recover from infection and wound-healing more slowly than their teetotaling counterparts, they're also more susceptible to pneumonia and at higher risk for both bacterial and viral infections and a range of medical conditions, including acute respiratory distress syndrome (ARDS), sepsis, alcoholic liver disease and certain cancers.
But what about moderate drinkers? That's a surprisingly different story, both in terms of any interference with the COVID vaccine and issues that go beyond it.
Research suggests there's a sweet spot when it comes to the health effects of drinking alcohol. Moderate drinking — meaning no more than two drinks a day for men and one per day for women — might actually benefit the immune system by reducing inflammation. (As a reminder: A drink is one 12-ounce beer, 5 ounces of wine or 1.5 ounces of 80-proof spirits like bourbon, vodka or gin.)
Venture beyond the moderate zone, however, and those benefits go by the wayside. “Everything you do has a risk-benefit ratio. With alcohol, the benefits outweigh the risks when you're talking about a very low amount of alcohol per day,” explains Amesh Adalja, an infectious disease doctor and senior scholar at the Johns Hopkins Center for Health Security at the Bloomberg School of Public Health in Baltimore. Exceed the one- or two-drink-per-day recommendation, and the balance shifts. “The complications of alcohol — in terms of liver disease, trauma — increase the risk and outweigh those benefits."
The COVID-19 connection
Although clinical trials of the various COVID-19 vaccines didn't look specifically at the impact of alcohol on immunity, researchers think the same principle applies. “We know from other studies that chronic alcohol consumption can lead to weak vaccine responses and reduce protection,” says Ilhem Messaoudi, director of the Center for Virus Research at the University of California, Irvine. “The same most likely applies to the COVID-19 vaccine. Those who drink in excess are likely to generate dampened immune responses and also be at higher risk of having severe COVID-19.”
"When we consume alcohol outside of the moderate zone, we see a significant increase in susceptibility to infection — especially respiratory pathogens — decreased wound-healing capacity and increased risk of cancer,” adds Messaoudi, who has studied the effects of alcohol on the immune response. Chronic heavy alcohol consumption, she says, gives you all of the inflammation with few of its benefits, since it “increases the production of inflammatory factors by immune cells while reducing their ability to fight infection. “
Researchers believe that's especially true among people over 50, since the immune system starts to slow down in its ability to fight infection and respond to vaccination around midlife.
Less is more
"Alcohol may have the ability to blunt immunity when people drink in large quantities, and a lot of that has to do with chronic use of alcohol versus acute use,” says Adalja, echoing the findings of a large review of studies published in Alcohol Research Current Reviews. “It's not as if you have one binge episode and that shatters your immunity. It's more that chronic drinkers do not respond as robustly to vaccines, or they're at risk of certain infections because of the effects that alcohol in high doses has had on their immune system.” In general, experts say, it isn't the occasional one (or two) too many that affects immunity but more the one glass too many nightly or the several too many weekly.
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As for drinking the night before or after you get vaccinated? “Mild to moderate alcohol intake is fine before and after the vaccine,” says Adalja, who adds they've seen no clinically significant impact on the vaccine with that type of drinking's immediate effect on the immune response (unlike the effect of chronic drinking).
But if you are pouring a glass around the time of your shot, keep in mind the issue of alcohol and vaccine side effects. If you're hung over the day you get vaccinated, for instance, you could be hard-pressed to separate out the responses caused by the shot from those caused by the night before. “It's important to keep distinct what's caused by the vaccine and what isn't,” Adalja adds. “I don't worry about the response to the vaccine so much as the mistaking the effects of alcohol intoxication for vaccine-related side effects.”