Share on Pinterest
Milan Markovic/Getty Images
  • Americans eligible for a COVID-19 booster are free to choose any authorized vaccine.
  • The CDC and FDA have focused on higher-risk groups when outlining who is eligible to get a COVID-19 booster.
  • Anyone who had an allergic or other severe reaction to a COVID-19 vaccine should check with their doctor first before getting a booster.

Last week the Centers for Disease Control and Prevention (CDC) approved the use of mix-and-match COVID-19 boosters for Americans at high risk of severe illness or infection.

Any of the three vaccines authorized in the United States — Pfizer-BioNTech, Moderna-NIAID, or Johnson & Johnson — may be used as a booster, regardless of which vaccine people received initially.

Here are a few things to keep in mind when choosing which vaccine to get as a booster.

Dr. Jay Varkey, an associate professor of infectious diseases at Emory University School of Medicine, said even though boosters are being rolled out in the Unites States, the vaccines are still working.

“They are very effective at preventing death from COVID, and they’re very effective at preventing serious illness that requires people to get hospitalized for COVID,” he said Friday in a media briefing.

“[Boosters are] really [about] trying to enhance protection from infection,” he added, especially for those most at risk.

The CDC and the Food and Drug Administration (FDA) have focused on these higher-risk groups when outlining who is eligible to get a COVID-19 booster.

Among people who received one of these mRNA vaccines, the following can get a booster at least 6 months after their initial series:

  • age 65 and older
  • age 18 to 64 with underlying medical conditions
  • age 18 to 64 who live in long-term care settings such as assisted-living facilities, inpatient psychiatric settings, group homes, or homeless shelters
  • age 18 to 64 who work in high-risk settings, including healthcare workers and other first responders, teachers and school support staff, and food and agricultural workers

Pregnant and recently pregnant people are at higher risk of severe COVID-19 and hospitalization if they contract the novel coronavirus, so the CDC includes them in the same group as people with underlying medical conditions.

Some people who are immunocompromised are eligible for a third dose; this is considered part of their initial series. Currently, the CDC does not recommend that they also get a booster.

The Pfizer-BioNTech booster is given as a full dose; the Moderna-NIAID booster is given as a half dose.

Anyone 18 years old or older who received the J&J vaccine is eligible for a booster at least 2 months after the first dose.

This wider eligibility is because a single dose of this vaccine offers less protection than two doses of an mRNA vaccine.

In September, the CDC recommended that the following groups who received the Pfizer-BioNTech vaccine should get a booster. The same guidelines will likely apply to the Moderna-NIAID booster.

  • age 65 and older
  • age 50 to 64 with underlying medical conditions
  • age 18 to 64 who live in a long-term care setting

Middle-aged and older adults with underlying medical conditions have a higher risk of severe illness if they contract an infection.

People living in a long-term care facility are at higher risk of coronavirus infection due to the close contact with many other people. Many of these people may also have chronic medical problems.

The CDC says other people who received an mRNA vaccine and are eligible for a booster may consider getting one, based on their personal risks and benefits.

In addition, the agency recommends that anyone who received the J&J vaccine should get a booster to bring the level of their protection in line with that offered by the mRNA vaccines.

The CDC is expected to release additional guidelines this week to help people decide whether and which booster to get, reports The Washington Post.

Right now, there’s very little scientific evidence to help people decide which booster to get.

Most of what’s available comes from a recent preprint study by the National Institutes of Health (NIH), which looked at mixing and matching boosters.

Researchers found that each of the authorized vaccines, when used as a booster, increased the level of antibodies in the blood, regardless of which vaccine people received during their initial series.

In a separate study, Pfizer and BioNTech found that a booster of their vaccine strongly protected against coronavirus infection. These results are also preliminary.

That means whichever vaccine you choose as a booster will increase your immune protection.

However, one thing that stood out in the NIH study is that people who started with J&J saw a larger jump in antibodies with an mRNA booster, compared to a second J&J dose.

“For persons who have received the J&J vaccine, getting a booster with one of the mRNA vaccines may be better than getting another J&J booster,” said Dr. Shobha Swaminathan, an associate professor and infectious disease physician at Rutgers New Jersey Medical School.

The data released so far from the NIH study is preliminary, and it only looks at one aspect of the immune response — antibodies.

“I don’t think we can draw firm conclusions in terms of one vaccine being better than the other,” said Varkey.

“[The NIH study] helps answer the question of what our antibodies do. But what [it] doesn’t answer is: ‘In the real world, does some magical combination [of vaccines] sort of better enhance protection?’” he said.

NIH researchers will release data at a later date on the effect of different boosters on memory cells, B cells, and T cells — the cellular immune response.

“Our immune systems are much more complex and robust than a simple measure of antibodies,” said Varkey. Over time, “we decrease our antibodies and we focus more on memory cells that protect us from dying.”

Individuals may also want to weigh the personal benefits and risks of each vaccine.

Men under 40 are at higher risk of heart inflammation — myocarditis and pericarditis — with the mRNA vaccines, so they may want to consider a J&J booster.

Most cases of heart inflammation after COVID-19 vaccination have been mild, with patients responding well to treatment.

Women under 50 may want to consider getting an mRNA booster, because the J&J vaccine is associated with a rare type of blood clot in that age group.

“If a young female were to need a booster, an mRNA booster may be better since it does not have the clotting risk,” said Swaminathan.

Anyone who had an allergic or other severe reaction to a COVID-19 vaccine should check with their doctor first before getting a booster.

Varkey suggests that people with questions about boosters seek out trusted medical advice.

“This decision on what to get boosted with will be an individual decision that most people should make with the advice of their doctor,” he said.