Boosters Are Not Going to ‘Destroy’ Your Immune System

The newest vaccine conspiracy theory is based on a decontextualized comment from a European official and tons of feverish speculation.
A blonde woman in a white mask receives a shot in her arm from a nurse in a white hat.
A teacher receives a shot during COVID-19 booster vaccination of teaching staff at Novosibirsk's secondary school No 169 on January 17, 2022 in Novosibirsk, Russia. Photo via Getty Images. 

From the start of the pandemic, the goal of vaccine conspiracy theories has been to falsely claim that COVID vaccines are either ineffective or actively harmful. Every new factoid that fits with that narrative is speedily incorporated, and the facts that don’t—for instance, that vaccinated people are far less likely to be hospitalized or die from COVID—is discarded. The newest thing being feverishly spun into the narrative is a comment from an official with the European Medicines Agency, who expressed concern that repeated vaccine boosters could potentially “overload” people’s immune systems. Infectious disease experts and epidemiologists tell Motherboard there’s no evidence that’s happening, or indeed could happen, and that a far greater concern lies with the huge number of people globally who remain totally unvaccinated. 


The current flurry of faux concern began following a January 11 briefing by the European Medicines Agency, where public health officials including Marco Cavaleri, the EMA’s head of biological health threats and vaccines strategy, took questions. At a couple of points, Cavaleri expressed hypothetical concern that repeated vaccine boosters every few months could create an immune response “that may not end up being as good as we would like to be,” he said.  

“If we have a strategy in which we give boosters, let’s say, every four months, approximately, we will end up potentially having problems with immune response, and it may end up not being as good as we would like it to be,” Cavaleri told journalists. “We should be careful in not overloading the immune system with repeated immunization. And secondly, of course, there is the risk of fatiguing the population with the continued administration of boosters.” 

That said, Cavaleri added, if boosters are the best option on the table “it can be done once or maybe twice” but “shouldn’t be repeated constantly.” In a scenario where COVID becomes less of a pandemic and more of an endemic disease, boosters could ideally be synchronized with the arrival of the cold season, similar to flu vaccines, he said. 

Predictably, this comment was plucked from the staid confines of a public health briefing and launched into the conspiracy stratosphere. “MASS MURDER CONFIRMED,” blared a post on Alex Jones’ profile on Gettr, the newish “anti-Big Tech” platform. “EU Official Admits COVID Vax Destroys immune System.” An article about Cavaleri’s comments was also shared in a QAnon-oriented Telegram channel with 50,000 followers, and the talking point that boosters leave one’s immune system wrecked are making the social media rounds. 


Cavaleri’s comments, taken out of context, fit neatly into the anti-vax narrative that vaccines will create a new variant of the virus or otherwise doom humanity. A previous version of these claims was promulgated by Dr. Geert Vanden Bossche, who wrote a widely circulated and utterly debunked manifesto claiming that COVID vaccines would somehow encourage COVID-19 to mutate, leading to new variants. Now, a new version of the same anxiety is being re-spun to include boosters; even before Cavaleri’s comments, in early January, QAnon promoter Dustin Nemos was claiming on his news network that “a study” proved COVID boosters are harmful. 

Experts, though, dismiss the idea that “overboosting” is a real thing that’s occurring, and have several theories about why this line of disinformation is gaining traction. 

“We’re not overboosting,” said Jessica Malaty Rivera. She’s an infectious disease epidemiologist, a senior adviser at the Pandemic Prevention Institute, and a research fellow at Boston Children’s Hospital. Even in the U.S., we’ve only recommended a single booster for those who have been fully vaccinated. There are instances where those who are immunocompromised are encouraged to get a fourth dose or a second booster; those are rare circumstances. And these are very small doses.” It’s not, she says, going to elicit “some dramatic immune responses that would cause the body to be harmed.”


Malaty Rivera added, “I think there’s a lot of confusion about what the booster will actually do. It’s not simply increasing your antibodies; it’s about enhancing the antibody response to be better at identifying new variants and reminding your body this is what the enemy looks like.” Vaccination also helps the body make T and B cells, she added, not just antibodies, all of which work together to create the body’s immune response. Boosters, Malaty Rivera said, “are about re-upping your immune response to give it more ability to recognize antigens over time. There’s not much data to suggest you can overboost in this case.” 

Rivera’s theory is that people are wrongly comparing boosters to antibiotics, since the concept of antibiotic resistance has become fairly well-known; it refers to when a bacteria (or viruses, fungi or parasites) change so that they’re no longer responsive to the antibiotic developed to fight them. The WHO has declared antibiotic resistance a “global health threat” and has said that misuse or overuse of antimicrobial products is partly to blame. For people with only a basic knowledge of science, the idea that “over-vaccination” could create resistance might be plausible, but it’s not real, she says.   


“Vaccines don’t cause variants,” she says. “You don’t create resistance by vaccinating. It’s not the same thing like a bacteria. You can’t create a superbug. I think it’s—people are confusing general concepts in science to make it sound like there’s a causal relationship between the variants and vaccines.” 

Dr. Paul Offit agrees. He’s an attending physician at Children’s Hospital of Philadelphia and a widely recognized expert on vaccines. (He also co-invented one himself, a vaccine against the rotavirus.) 

“Frequent boosting won't ‘damage’ the immune system,”he wrote in an email—which isn’t to say that there aren’t concerns with giving the same booster over and over, he added. “One theoretical concern is that as you continue to stimulate the immune system with the same antigen, it can make it more difficult to respond to subtle antigenic differences with the same virus, as is seen with influenza vaccines. This phenomenon is called ‘original antigenic sin.’” (It would follow that this is an argument for reformulating boosters to tailor them to emerging strains of COVID, not to stop boosting at all.) 

In the end, Offit said, a “booster won't overload the immune system.” He thinks that Cavaleri may have been referring simply to the idea that future booster doses wouldn’t pack the same punch: “Sometimes you get a lesser response with subsequent doses.” 


It’s also worth noting that the EMA also didn’t, at any point, suggest that vaccines or first booster doses are a bad idea. In the same press conference, Cavaleri also separately expressed support for booster doses, saying a booster “restores or extends protection.” It’s clear, in context, that Cavaleri was urging caution, and a thoughtful approach to long-term management of COVID.  “Repeated vaccinations within short intervals would not represent a sustainable long term strategy,” he said in his opening remarks. 

“I think what this comment was intended to do was to urge caution,” said Malaty Rivera—specifically, caution against stressing boosters for the already-vaccinated, when the far more important task is to get the unvaccinated world protected. “ I know Israel is on the fourth dose and I think they’re trying to urge caution against going into the fifth,” she said. “There has to be a vaccine equity aspect of this too. That’s an unfathomable concept, to be going beyond third doses when most of the world has yet to see first doses.” 

In the end, Malaty Rivera said, the goal needs to be finding ways to make COVID “less disruptive.” Vaccines, she said, “can’t be reupped all the time for the purpose of preventing symptomatic illness.” Some level of symptomatic illness is inevitable, infectious disease experts agree, given how widely COVID has circulated. The main goal of vaccination programs is to prevent severe illness, hospitalization, and death. 

In that rubric, Malaty Rivera said, there’s space to recognize that some people will choose to never get vaccinated. “A desire for 100% protection isn’t just the goal, nor should it be,” she said. “There’s always going to be population who are unwilling to get vaccinated.” While the self-appointed public health experts of Telegram and InfoWars try to frighten their audiences into avoiding even a basic level of protection, experts like Malaty Rivera are focused on how to live with COVID, and how to keep it from further destabilizing the world. 

“Even those in the public health space know that endemicity is not failure,” she said. “Circulating SARS-CoV-2 is an acceptable outcome, but we need to make sure it’s not destabilizing our livelihoods and healthcare systems.”