NEWS

Are Booster Shots Common for Vaccines?

Older man looking at his arm where he was vaccinated.

Jasmin Merdan / Getty Images

Key Takeaways

  • Booster shots are now approved for all three COVID-19 vaccines available in the U.S.
  • The Centers for Disease Control and Prevention (CDC) recommends a booster for all adults who completed their initial COVID-19 vaccine series and a third dose for certain immunocompromised persons.
  • Adults who meet eligibility criteria can choose any of the three authorized booster shots, although the Pfizer and Moderna mRNA COVID-19 vaccines are preferred.
  • Those age 12 to 17 years old can receive a Pfizer booster shot five months after they complete their initial Pfizer vaccination series.
  • Experts say boosters for vaccines are relatively common and sometimes necessary for bolstering protection against a virus or disease.
  • You’ve likely received a booster shot before—for example, adults should receive tetanus shots every ten years.


President Joe Biden announced on August 18 that booster shots would become available in mid-September for certain adults who have been fully vaccinated against COVID-19.

The Food and Drug Administration (FDA) has since authorized a booster dose for all three COVID-19 vaccines available in the U.S.

On November 19, the FDA amended its emergency use authorization (EUA) for both the Pfizer and Moderna COVID-19 vaccines, approving the use of a single booster dose for all persons 18 years and older who completed the primary series. The FDA later authorized a Pfizer booster shot for adolescents ages 12 to 17 who completed their initial Pfizer vaccination series.

The agency had previously authorized a booster for all adults who received one shot of the Johnson & Johnson vaccine and for specific groups of people at increased risk for COVID-19 exposure or severe illness.

At this time, the CDC recommends a COVID-19 booster for everyone 18 years and older who:

  • Completed the Pfizer or Moderna primary vaccine series at least five months ago.
  • Received the Johnson & Johnson vaccine at least two months ago.

Additionally, the CDC recommends those 12 to 17 years old receive a Pfizer booster shot if they completed the Pfizer primary vaccination series at least five months prior.

Eligible adults are able to choose any authorized COVID-19 booster. However, it is now recommended that individuals get the Pfizer or Moderna mRNA COVID-19 vaccine over the Johnson & Johnson vaccine, following concerns about blood-clotting side effects. The Johnson & Johnson shot still remains an option for those who are not able or willing to get a different vaccine.

Adolescents ages 12 to 17 who completed Pfizer's primary series are only eligible for the Pfizer booster.

The Pfizer and Johnson & Johnson boosters will be administered with the same dosage as the initial vaccine, whereas Moderna’s will be a half dose (50 micrograms).

While COVID-19 is a new virus, the idea of booster shots isn’t. Verywell spoke to experts about the use of booster shots for other routine vaccines you may be familiar with.

Booster Shots Are Common

According to Jason C. Gallagher, PharmD, FCCP, FIDP, FIDSA, BCPS, clinical professor at Temple University’s School of Pharmacy and clinical specialist in infectious diseases, boosters are common.

“Most vaccines that are given in the U.S. require several doses to render immunity,” Gallagher tells Verywell. “I like to think of [a COVID-19 vaccine booster] as the third dose of a multi-dose series.”

While boosters are common, whether they’re necessary largely depends on the type of vaccine, Jeffrey Langland, PhD, virologist and professor at Southwest College of Naturopathic Medicine, tells Verywell.

“Most vaccines that do not contain a live, attenuated (weakened) virus, typically require multiple doses or boosters,” Langland says.

One dose of some live vaccines can offer you a lifetime of protection against disease. Other live vaccines may require two doses, like the measles, mumps, and rubella (MMR) and chickenpox vaccines. Children typically get their first dose at 12–15 months old and their second (and final) dose between age 4–6.

But other types, like inactivated vaccines, will need several doses over time to remain effective. Boosters are currently recommended for several vaccines—chances are you’ve likely received one in your lifetime.

For example, adults should receive a tetanus vaccine—a recommended series of childhood and adult immunizations to protect against lockjaw—every ten years. You’re recommended to get others, like the flu shot, annually.

“We give the influenza vaccine annually since the virus constantly evolves, and we work to catch up with strains that dominate,” Gallagher says.

You start receiving boosters at an early age, Langland notes. These childhood vaccinations include:

  • Pneumococcal: three doses at two, four, and six months; boosters at 12 to15 months.
  • Haemophilus influenzae type b (Hib): two doses by four months; boosters at 12 to 15 months
  • Polio: three doses by 18 months; boosters at four to six years—depending on which vaccine is used.

Although most of these vaccines offer strong protection against diseases, the immunity offered by the shots often wanes over time. That’s where boosters come in.

Additional doses help amplify the body’s immune response. “A second or even third dose is given to boost the immune response, and it is this response that really primes the immune system to tackle the disease when it is encountered,” Gallagher says.

Because both the COVID-19 virus and vaccines are new, Langland says scientists are still learning about the duration of protection offered by the shots. But some data suggests the vaccines may now be offering reduced protection against mild and moderate disease with the rise of the Delta variant.

“We are still learning how long either natural immune memory lasts after a natural infection and how long it lasts after the vaccine,” Langland says. “The boosters help the immune system learn about the virus better and better each time a booster is received.”

What This Means For You

You are eligible for a COVID-19 booster vaccine if you are 18 years and older and:

  • Completed the COVID-19 mRNA vaccination series at least five months ago.
  • Received a Johnson & Johnson vaccine at least two months ago.

If you are 12 to 17 years old, you can only receive a Pfizer booster shot if you completed the initial Pfizer vaccination series at least five months ago.

If you’re immunocompromised, talk to your doctor about getting a third dose now.

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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7 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Food and Drug Administration. Coronavirus (COVID-19) update: FDA expands eligibility for COVID-19 vaccine boosters.

  2. Food and Drug Administration. Coronavirus (COVID-19) update: FDA takes multiple actions to expand use of Pfizer-BioNTech COVID-19 vaccine.

  3. Centers for Disease Control and Prevention. COVID-19 vaccine booster shots.

  4. Centers for Disease Control and Prevention. CDC endorses ACIP’s updated COVID-19 vaccine recommendations.

  5. Department of Health and Human Services. Vaccine types.

  6. Centers for Disease Control and Prevention. Measles, mumps, and rubella (MMR) vaccination: what everyone should know.

  7. Centers for Disease Control and Prevention. Who is eligible for a COVID-19 vaccine booster shot?