Is the COVID-19 Vaccine Safe for Everyone? Here's Who Should (and Shouldn't) Get It

In August 2021, the US Food and Drug Administration (FDA) granted full approval of the Pfizer-BioNTech COVID-19 vaccine for use in people as young as 16. This was the first of the vaccines to be fully approved in the US. A few months later in January 2022, the FDA also granted full approval to Moderna's vaccine for those ages 18 and up. And in October 2021, the FDA authorized the Pfizer vaccine for children ages 5-11.

Full approval is different from emergency use authorizations (EAU). EAU is the level at which all the vaccines started out, and means that they were authorized for use in an emergency situation—in this case, the COVID-19 pandemic—after initial testing for safety and effectiveness.

While many have widely praised the vaccines and the scientists behind them for their speed in development and rigorous testing through vaccine trials, some still have questions about vaccine safety, especially in specific groups. Here's what you need to know.

How Do We Know a Vaccine Is Safe?

First and foremost: The CDC maintains that the US has a vaccine safety system that ensures all vaccines are as safe as possible. It's why the FDA was able to grant emergency use authorizations for both the Pfizer and Moderna COVID-19 vaccines after data from manufacturers and large clinical trials demonstrated that the potential benefits of the vaccines outweighed the known and potential harms of coming down with COVID-19.

When it comes to the safety testing in vaccine clinical trials—aka, determining whether the vaccine is safe to use in those participating in the trials, versus whether or not its effective—researchers track vaccine participants' health throughout the trial, Megan Ranney, MD, MPH, an emergency physician and director for the Brown-Lifespan Center for Digital Health at Brown University, told Health. Any time they get sick, hospitalized, or even die, experts investigate whether it had any possible ties to the vaccine. Trials like the ones for the Pfizer and Moderna COVID-19 vaccines also have independent monitoring boards made up of people with no ties to the studies. "Their only job is to make sure that the drug is safe," said Dr. Ranney.

It's also important to note that "safe" doesn't mean "zero side effects." Rather, Dr. Ranney explained, a vaccine is considered safe when it doesn't cause serious adverse events. "An 'unsafe' vaccine is one that causes permanent or serious harm—things that change the course of a person's life," said Dr. Ranney. Those things can include changing fertility, causing neurological problems, or causing new infections. So, regarding the mild side effects that can accompany the coronavirus vaccine—fatigue, headaches, arm pain—they're a small price to pay to potentially avoid COVID-19's more serious symptoms and risks, and therefore don't worry doctors, said Dr. Ranney.

Further, it's possible that mRNA vaccines could be safer in some ways than traditional vaccines. Traditional vaccines typically contain common allergens, like eggs or metals. The mRNA vaccines don't contain these ingredients, which may open them up to people who have had to forgo vaccination in the past due to allergies to them.

This doesn't mean, however, that the mRNA vaccines have no potential to cause an allergic or other adverse reaction. People with a history of severe allergic reactions are being urged to use caution if and when they get the vaccine. And the CDC says that those who have had severe allergic reactions to any ingredients in any of the COVID-19 vaccines should not get the vaccine.

Others who have had severe allergic reactions of any kind in the past—not related to vaccines in general—are urged to still get the vaccine, but with the proper safeguards in place—including on-site monitoring by a medical professional who has access to emergency medications like epinephrine or antihistamines. "Right now there is no reason to avoid getting the vaccine just because you have a history of allergies," said Dr. Ranney, though it's worth bringing up previous reactions to vaccines to your doctor and the person giving you the injection.

Of note: According to the CDC, they have found at least four types of serious adverse reactions that are linked to certain types of COVID-19 vaccines. These serious adverse reactions include anaphylaxis, thrombosis with thrombocytopenia syndrome (TTS), myocarditis and pericarditis, and Guillian-Barré Syndrome (GBS). It's important that anyone who experiences an adverse reaction (which includes these or any other reactions) report them to their doctor and to the CDC's Vaccine Adverse Event Reporting System (VAERS). This will help in the continued effort to keep vaccines as safe as possible for as many people as possible.

So Who Has the Vaccine Been Approved for—and Which Groups Still Need More Info?

The initial clinical trials for both vaccines excluded a number of specific groups, including pregnant or breastfeeding people and children—though that's not necessarily an uncommon practice. "Pregnant [people] and children are considered vulnerable populations. You have to have pretty good proof that something works before you're allowed to do trials of new drugs with them," said Dr. Ranney.

And even though pregnant and breastfeeding people weren't specifically recruited to participate in clinical trials, it doesn't mean they were entirely absent from them. "Generally, vaccines are not intentionally tested in pregnant [people] and that data usually is accumulated over time as pregnant [people] get vaccinated accidentally or they choose to get vaccinated," Otto Yang, MD, professor of medicine in the division of infectious disease at the David Geffen School of Medicine at UCLA, told Health.

While pregnant and breastfeeding people weren't included in trials, the CDC says the vaccines are safe for this population. The American College of Obstetricians and Gynecologists (ACOG), too, trusts in the safety of the vaccines and recommends that all eligible people, 12 years old and up, including pregnant and breastfeeding individuals, get a COVID-19 vaccine or series of vaccines. In October 2021, the FDA also authorized the Pfizer vaccine for children 5-12 years of age, and the CDC endorsed vaccines in this age group in November 2021.

Another population group that the vaccines weren't specifically tested on were immunocompromised people or those who are on immunosuppressants—but that's due to concern about efficiently testing the vaccine rather than concern about safety, said Dr. Ranney. "You worry that they're not able to mount as good of an immune response, so testing the vaccine in them is going to show less effect of the vaccine than you would expect," explained Dr. Ranney.

However, some immune-compromised groups were included in phase II and III trials after activist groups and research organizations protested that people with well-controlled HIV shouldn't be considered immunodeficient (because the medications they take strengthen their immune systems). No safety concerns from those groups were reported, but the number of participants was very small, so it's not a great predictor for the HIV community as a whole. Ultimately, it's up to those who are somehow immunocompromised and their doctors to decide if they should get the vaccine.

Overall right now, Dr. Ranney stated that there's no reason to believe that either COVID-19 vaccine would be unsafe—as in, cause severe harm—for the large majority of people, including any groups who were left out of clinical trials. If you have any questions about if or when you should get the COVID-19 vaccine, it's best to speak to your doctor and bring up any possible concerns.

The information in this story is accurate as of press time. However, as the situation surrounding COVID-19 continues to evolve, it's possible that some data have changed since publication. While Health is trying to keep our stories as up-to-date as possible, we also encourage readers to stay informed on news and recommendations for their own communities by using the CDC, WHO, and their local public health department as resources.