Are COVID Boosters Safe? What the Science Says

An updated round of COVID-19 booster vaccines was approved by the U.S. Food and Drug Administration (FDA) on Monday, with doses becoming available as early as the end of this week.

The announcement comes amid a recent surge in COVID cases and hospitalizations. In the past two months, weekly COVID-19 hospitalizations have more than doubled, according to the U.S. Centers for Disease Control and Prevention (CDC).

However, the FDA's announcement has led many to question the necessity of these booster vaccines, with others raising concerns about their safety. So what do the scientists say? Newsweek spoke to three vaccine experts to find out.

What Are Booster Vaccines?

Vaccinations work by imitating an infection. The first vaccination acts to prime the immune system against distinctive spike proteins on the virus's surface.

In response to these proteins, our body produces an armory of antibodies that are designed to destroy SARS-CoV-2 (or whatever the target infection is for that particular vaccine). However, these antibodies naturally decrease over time. Boosters act as a way of reminding our bodies what that initial spike protein looked like in order to kick-start our immune response and build back our antibody arsenal.

Over time, viruses are able to change their spike proteins so that the original antibodies are less well adapted to recognize them. Therefore, boosters may also be updated over time to better handle the most dominant virus strains at the time and adapt to the virus's ever-changing disguise.

What Are the Concerns About New COVID Boosters?

Despite the overwhelming safety profile of previous COVID-19 vaccinations, some people are still concerned about the safety of these additional vaccinations.

"The big safety issue is, of course, myocarditis [heart inflammation]," William Schaffner, a professor of preventive medicine and infectious disease at the Vanderbilt University Medical Center, told Newsweek. "But myocarditis is first a rare event. Number two, it is overwhelmingly very mild, and the people who experience it [usually] recover.

"This is a very, very low risk considering the much higher risk of myocarditis after COVID itself, which often is forgotten. If you're going to get COVID, you're at a much greater risk of getting myocarditis than after the vaccine," he said.

Since the vaccines were first put into circulation in December 2020, scientists have been able to observe and update the side effects associated with them. "The reality is that we have had these vaccines for almost three years," Ziyad Al-Aly, a senior clinical epidemiologist at Washington University in St. Louis, told Newsweek. "Hundreds of millions of people around the world have received them. They are safe, and their effectiveness exceeded expectations."

He continued: "Side effects are real and they happen, but at an exceedingly low frequency. Most if not all cases of myocarditis after COVID-19 vaccine are self-resolving. The critical question people should think about is benefit versus risk. We know vaccines reduce the risk of severe illness, hospitalization and death, and the risks of adverse events are exceedingly low."

However, some have raised specific concerns about the most recent booster update.

"There's been no clinical trial done in human beings showing that it benefits people," Florida Surgeon General Joseph Ladapo said in a news conference. "There's been no clinical trial showing that it is a safe product for people."

However, the key point here is that the updated booster is not an entirely new vaccine—it is a minor tweak to the ones that already exist. "We know exactly what the safety profile of these vaccines is," Schaffner said. "They are no longer new vaccines, and they have been scrutinized for safety, much more than many of the other vaccines that are currently available."

This is also not the first time we have updated vaccines in this way.

"We have precedents for doing this," Schaffner said. "Look at influenza. The influenza vaccine is something that we use in millions upon millions of doses around the world on an annual basis. And we update that vaccine using the same process each year. And those updated vaccines are not tested in people, but their manufacture is under the very intense scrutiny of the FDA. We're doing the same thing with [COVID] vaccines."

Paul Offit, a pediatrician at Children's Hospital of Philadelphia, who sits on the FDA's vaccine advisory group, described Ladapo's reasoning as a "straw man argument."

"It's really no different to the influenza vaccine.... It's all brought on to scare people about the safety of this vaccine," he told Newsweek. "When you have more than 13 billion doses of this vaccine given throughout the world, I think we know exactly what its safety profile is. It's very safe."

Who Should Get a COVID Booster?

While most doctors and scientists agree that the vaccine is safe, the main debate today is over who should be receiving these booster doses.

"There are two schools of thought," Schaffner said. "There's one school of thought that paints with a very broad brush. They say, Let's make this vaccine a routine recommendation for the broadest population that we can. In other words, let's remain consistent with what the current recommendations are, namely that everyone 6 months of age or older is eligible for this vaccine.

"The other point of view you will hear is more targeted, risk-based recommendations, focusing on people at higher risk," he said. "Where people are at higher risk, make [the booster] routine for them, and then say that anybody else who wants to receive the vaccine can request to receive it."

Offit said that this second approach had been taken successfully by several European countries, such as the U.K. and Germany. "The goal of this vaccine is to prevent serious illness," he said. "So the question now is: Who's getting hospitalized and who's dying from this virus?

"It really falls into several high-risk groups: people who are elderly; people with multiple health problems like obesity, chronic lung disease, heart disease, kidney disease, liver disease; people who have diabetes; people who are immunocompromised; and pregnant people," he said.

These people would also be included in a broad spectrum recommendation, but Offit said that this might not be as effective. "I think when you say everybody benefits you dilute the message," he said. "Wouldn't it make sense, if we wanted to try to get those high-risk groups immunized, to really focus messaging on those high-risk groups?

The second issue with broad-spectrum booster recommendations is the cost. "Who pays for it?" Offit asked. "The government does have a little over $1.1 billion program where, if you're uninsured or underinsured and you are recommended to receive the vaccine, you can get it. But there's another reason why it makes more sense to target high-risk groups. So that we can get those people vaccinated who are most likely to benefit."

However, not everyone who has been hospitalized with COVID-19 would fall into this high-risk category. And yet, such people clearly are at risk of severe disease. "If you are young and strong and do not have an underlying illness, your risk of serious disease is really very low," Schaffner said. "But it is not zero."

Al-Aly agreed, saying: "In my opinion, people older than 12 years old should consider a booster."

What's more, even mild cases of COVID can result in long-term symptoms after the initial infection has cleared. "The proponents of universal vaccination will point out that not only do you reduce the risk of severe disease through the vaccine but you also reduce the risk of long COVID," Schaffner said.

The CDC was expected to announce who should be getting these updated vaccinations on Tuesday afternoon.

Whatever the final consensus, vaccine experts agree that if you fall into any of these high-risk groups, a booster shot is a safe and effective way to reduce your risk of severe COVID-19.

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