Are COVID-19 Booster Shots Variant-Specific?

A bunch of vaccine ampules lined up; they are labeled COVID-19 vaccine.


Key Takeaways

  • Booster shots may soon become available to individuals who are eight months out from their second dose of the Pfizer-BioNTech or Moderna vaccines.
  • Vaccine booster shots will be in the same formulation as previous doses.
  • Boosters of the mRNA vaccines have already been authorized by the Food and Drug Administration (FDA) for some people who are immunocompromised at the same dose as the original vaccines. The general public, however, may receive half doses of Moderna boosters.
  • More data is needed before the Centers for Disease Control and Prevention (CDC) can recommend a booster dose of the one-shot Johnson & Johnson vaccine.

The rollout of COVID-19 booster shots for some vaccine recipients may begin in late September. A third dose of the Pfizer-BioNTech and Moderna vaccines has already been authorized by the Food and Drug Administration (FDA) for immunocompromised people who meet certain criteria.

While vaccine makers are developing and testing next-generation COVID-19 vaccines that will offer better protection against variants of the virus, for now, booster shots won't be different from what people are already familiar with.

Philip Felgner, PhD, the director of the University of California, Irvine Vaccine Research and Development Center, tells Verywell that boosters will be “exactly the same" as what vaccinated people got the first time around.

Same Shot, Different Day

In August, the FDA authorized a third vaccine dose for immunocompromised individuals who meet certain criteria. These people will be able to get a third dose of either the Pfizer-BioNTech or the Moderna vaccine—depending on which vaccine they initially received. The FDA has not yet authorized a second, booster dose of the one-shot Johnson & Johnson vaccine

Shortly after the FDA’s authorization of third doses of the mRNA vaccines for immunocompromised people, President Biden announced a potential booster plan for other vaccinated people to start as soon as September 20.

The White House had originally stated that a person would be able to get a booster dose eight months after becoming fully vaccinated, but that plan is on hold because the FDA has not yet officially authorized boosters. 

Whether someone is receiving the third dose as an immunocompromised person or a booster dose that's based on the timing of their last vaccine dose, Felgner says that the shots will be the same formulation as the ones people got before. While Pfizier-BioNTech applied for authorization of its booster shot at the same dosage as the original vaccine, Moderna's booster application is for a 50-microgram dose—half of the initial dosage.

Third Dose vs. Boosters

The Centers for Disease Control and Prevention’s Advisory Committee on Immunization Practices (ACIP) has been clear about the distinction between a third vaccine dose and a booster shot.

The CDC states that “an additional dose is for people who may not have responded adequately to the initial two-dose regimen, specifically those who are moderate to severely immunocompromised.”

In a statement released on September 2, Kristen Nichols, PharmD, BCPS, BCPPS, BCIDP, a Senior Content Management Consultant, Pediatric Infectious Diseases, for Wolters Kluwer, defined booster shots as “doses that are given to people who likely had an adequate initial response but whose immunity may have waned over time."

Nichols clarified that boosters are for "your typical healthy person who got vaccinated originally but now needs to ‘re-invigorate' that protection.”

Tackling Variants With Vaccines

While the boosters are more of the same, we may see updated COVID vaccines in the future. “The technology is very agile,” says Felgner. “And they will be able to change it or modify it and then make the next generation version as the virus mutates.”

In a press release, Pfizer-BioNTech announced that it is currently developing a COVID vaccine that “targets the full spike protein of the Delta variant." The updated version still needs to be thoroughly tested and vetted, and clinical trials are underway.

A new vaccine is not part of the White House booster rollout plan, and updates likely will not be called a "booster" shot.

"If we approach new COVID vaccines that target variants like we do the seasonal flu shot, it wouldn’t necessarily have a specific term," says Nichols. "New strains are incorporated into the flu vaccine each year based on which strains are expected to be circulating, and we continue to call that just the influenza vaccine."

Will Boosters Work Against Variants?

Early data on booster doses of the Pfizer-BioNTech and Moderna vaccines has been promising, but there are still some unknowns because of the virus variants that continue to emerge.

Pfizer and BioNTech have submitted early-stage clinical trial data to the FDA, with Phase 3 data expected to come soon. In the trials, participants received a booster shot eight to nine months after their second dose.

According to a press release, the results showed that the third dose “elicited significantly higher neutralizing antibodies” against the initial SARS-CoV-2 strain as well as the Beta and Delta variants.

Moderna has also initiated the data submission process of early clinical trial data. For the Phase 2 clinical trial, participants received a booster dose six months after getting their second dose. In a press release, Stéphane Bancel, Moderna CEO, said that the booster showed “robust antibody responses against the Delta variant."

The CDC says that people who received the one-dose Johnson & Johnson COVID-19 vaccine will likely need a second dose as a booster. However, data in support of the recommendation is not yet available, though it's expected in the coming weeks.

As boosters begin to roll out for people who are already vaccinated, it’s important for those who are unvaccinated to initiate their first dose.

“This vaccine is very effective even with the Delta variant that is so aggressive,” says Felgner. "It’s able to prevent the severest form of coronavirus infection.” 

What This Means For You

If you received the last of your two-dose COVID-19 vaccine eight months ago, you might be eligible for a booster shot soon, pending FDA authorization. If you’re immunocompromised, talk to your doctor about getting a third dose now.

If you received a one-dose Johnson & Johnson vaccine, information about boosters is expected in the coming weeks.

The information in this article is current as of the date listed, which means newer information may be available when you read this. For the most recent updates on COVID-19, visit our coronavirus news page.

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  1. Centers for Disease Control and Prevention. COVID-19 vaccine booster shot. Updated September 1, 2021.