Why four or five drinks could affect your COVID-19 vaccine response

"Binge drinking" can impact immune system
Alcohol and COVID-19 vaccination
Posted at 11:51 AM, Mar 04, 2021

SAN DIEGO (KGTV) -- Research has shown alcohol can affect the immune system, but there’s debate among health experts about whether drinking could impact the COVID-19 vaccines.

There are no published studies on whether alcohol decreases the effectiveness or intensifies the side effects of the COVID-19 vaccines. The FDA and CDC have offered no formal guidance that people curtail drinking before or after the shots.

Studies on alcohol and the effectiveness of other vaccines offer mixed results. One study found long-term, heavy drinkers produced fewer antibodies to the pneumococcal vaccine. But what about just a few drinks before or after the shot?

Many U.S. doctors have suggested that one or two drinks won’t significantly affect the immune response. But four or five drinks? That’s another story.

Four drinks in a single sitting is the definition of binge drinking for women; five drinks is the threshold for men. Just one episode of binge drinking can cause short-term effects in the immune system, a 2015 study found.

The study found the immune system begins to change within minutes, beginning with increased inflammation. Within two hours, the authors detected a drop in the number of circulating monocytes, a type of white blood cell that plays a role in both the innate and adaptive immune responses. The adaptive immune response is the one targeted by vaccines.

“If [monocytes are] getting knocked down by a whole bunch of binge drinking, then yes, [the vaccine is] not going to work as well,” said Dr. Christian Ramers of Family Health Centers of San Diego. “So I think it's theoretically plausible that alcohol could impair, ultimately, your ability to respond to the vaccine, or to any other infection for that matter.”

Notice the “theoretically plausible.” Dr. Ramers is the first to point out that the evidence in this area is very thin. But the National Institutes of Health notes that “alcohol in the body at the time of exposure to a pathogen tends to impair the body’s immediate immune response to the pathogen.”

At some level, vaccination is a way of presenting a fake pathogen to the body to stimulate an immune response.

“People have probably experienced this,” Dr. Ramers said. “After drinking too much, they are more susceptible to infection. And it's not going to give you the nice, robust response to that vaccine.”

In the absence of firm evidence, health experts have offered some conservative recommendations. One group in the UK recommends people avoid alcohol two days before vaccination and up to two weeks after to ensure the maximum immune response.

Dr. Mark Sawyer, a member of the FDA’s vaccine advisory committee, was skeptical about the need to abstain from alcohol entirely.

“I think it’s plausible a binge drink in particular could cause a temporary effect, but again, I don’t think it’s going to be of a substantial nature,” he said.

Then there’s the question of side effects. A few ABC10 News viewers said they had celebratory drinks after their second doses and experienced intense side effects.

“No doubt these vaccines cause an array of short-term side effects. Some people get headaches, some people get light-headed, some people hear ringing in their ears. Nausea. All things that could overlap with symptoms with alcohol, especially too much alcohol,” said Dr. Sawyer.

However, he said overlapping symptoms are not the same thing as alcohol triggering some kind of vaccine reaction -- there’s no evidence of that. Second doses of the vaccine tend to produce stronger side effects anyway, a signal that the body’s immune system is activated.

Bottom line: there are no official restrictions on alcohol use and the vaccines, but limiting alcohol can help ensure your immune system is in top shape, said Dr. Peter Chin-Hong, an infectious disease specialist at UC San Francisco.

“I think if you do it, do it in moderation,” he said.

This story originally reported by Derek Staahl on