Here's Why You Need a COVID-19 Booster Shot

A pattern of COVID-19 vaccine ampules on a light green background.

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Key Takeaways

  • The Food and Drug Administration (FDA) has granted emergency use authorization (EUA) for a booster dose of the Pfizer-BioNTech, Moderna, and Johnson & Johnson COVID-19 vaccines.
  • The Moderna, Pfizer-BioNTech, and Johnson & Johnson vaccines do provide protection against the virus strains circulating in the U.S. and are highly effective at reducing hospitalizations and deaths.

Studies have shown that booster shots can help restore waning vaccine-induced immunity and provide protection against a range of COVID-19 variants.

Previous variants have been shown to reduce the effectiveness of the COVID-19 vaccines that are currently available—and future variants might as well.

While vaccine makers are exploring the possibility of variant-specific vaccines, the most effective way to stay protected against any type of COVID right now is to get a booster shot of the existing vaccines once you're eligible.

In September, the FDA granted emergency use authorization for a booster dose of the Pfizer-BioNTech vaccine, but only for select vaccine recipients. On October 20, the FDA expanded its emergency use authorization to include the Moderna and Johnson & Johnson COVID-19 booster vaccines.

Soon after, the FDA authorized a booster dose for all adults who completed their initial COVID-19 vaccine series and a Pfizer booster dose for adolescents ages 12 to 17 who completed the initial Pfizer vaccination series at least five months prior. Eligibility was then expanded to include those 5 years and older.

The CDC recommends a first COVID-19 booster for everyone 5 years and older who:

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

According to the CDC, 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.

Children and adolescents ages 5 to 17 who completed Pfizer's primary series are only eligible for the Pfizer booster.

Moderately or severely immunocompromised persons 12 and older should receive an additional dose of the mRNA vaccine 28 or more days after completing the two-dose mRNA series or the one-dose Johnson & Johnson vaccine. A first booster shot is recommended three months after receiving a third (additional) dose of the Pfizer or Moderna COVID-19 vaccine or two months after getting a second (additional) dose if the first dose was the Johnson & Johnson vaccine.

The FDA has also authorized a second mRNA booster dose for certain individuals at increased risk for severe COVID-19 illness.

Persons 12 years and older who are immunocompromised for certain reasons and all adults 50 and older should receive a second mRNA booster dose four months after their first booster dose.

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).

In a statement released on April 20, Moderna's chief executive officer Stéphane Bancel said that “recent preclinical results have shown that our variant-specific booster candidates were effective against COVID-19 variants of concern, and we hope to continue to see positive results from the clinical studies.”

Moderna’s variant-specific vaccine candidates include one specifically targeted against the Beta variant and a multivalent booster (for any variant) that combines the company’s original vaccine and their shot offering protection against Beta in a single dose.

Moderna notes that its current vaccine provides neutralizing activity against current variants of the virus, but that booster doses are intended to increase that immunity.

How Much of a Threat Are Variants?

The CDC created four classifications for SARS-CoV-2 variants:

  • Variants being monitored (VBM): Variants that have or may pose a threat to approved or authorized medical countermeasures or have been associated with more severe disease (e.g., increased hospitalizations or deaths) or increased transmission but no longer poses a significant risk to the public.
  • Variant of interest (VOI): A variant with specific genetic markers that are associated with changes to receptor binding, increased resistance to antibodies created by previous infection or vaccination, or reduced efficacy of treatments. A VOI may also have an increase in transmissibility or disease severity and potential diagnostic failures.
  • Variant of concern (VOC): A variant showing increased transmissibility, more severe disease, diagnostic detection failures. or a significant reduction in neutralization by antibodies generated during previous infection or vaccination. A VOC may also show evidence of a substantial reduction in the effectiveness of one or more classes of treatment therapies.
  • Variant of high consequence (VOHC): A variant with clear evidence showing that prevention and medical measures have significantly reduced effectiveness relative to previous variants.

In the U.S., the Omicron variant is the only variant of concern. Currently, there is no variant of interest or of high consequence.

Waning Immunity

Because immunity created by most vaccines wanes with time, booster shots are a necessity. It is not unusual for vaccines to require boosters in order to maintain high levels of immunity.

In an interview with CNBC, BioNTech’s co-founder and chief medical office, Ozlem Tureci, MD, said that she expects people will need to be vaccinated against SARS-CoV-2 annually because of the decrease in immunity.

During a Johns Hopkins press conference, Naor Bar-Zeev, PhD, MPH, associate professor in the department of international health and the deputy director of the International Vaccine Access Center at Johns Hopkins Bloomberg School of Public Health, pointed out that “we have to have a tetanus shot every 10 years ."

Bar-Zeev said that boosters become “all the more [important] in the current context of variants emerging. We will have the opportunity to reboost, to revaccinate, and to broaden our protection, and not only make it more long-lasting.”

During the same press conference, Durbin noted that combinations of the different existing vaccines are already being tested. In the U.K., researchers are combining mRNA vaccines (like the Moderna and Pfizer-BioNTech) with a dose of an adenovirus-based vaccine (like the Johnson & Johnson vaccine) later on as a sort of booster shot—or vice versa.

“The best way to reduce the emergence of variants and their dominance across the world is to reduce transmission of the virus in populations everywhere,” Bar-Zeev said. “And that can be achieved through high coverage with the existing vaccines. It can be achieved through maximizing the breadth of vaccine products that are available, maximizing their production, and maximizing their delivery around the world.”

Durbin added that vaccines are also important strategies for reducing the risk of severe illness and hospitalization from COVID-19, as well as deaths. “These are the critical efficacy endpoints that will make a public health impact and get us out of this pandemic,” Durbin said. “The vaccines are providing us light at the end of the tunnel, but we need to ensure global vaccine access because we will not be entirely out of the pandemic until the world is vaccinated.”

Vaccines Alone Are Not Enough

Bar-Zeev cautioned against viewing vaccines alone as being enough to turn the COVID-19 pandemic around. “Vaccines are enormously powerful tools in public health, but they’re not the only tool.”

As vaccination efforts continue, Bar-Zeev stated that “we need to maximize every tool we have at our disposal, and that does include masks and it includes distancing, and it includes public restrictions where appropriate.”

What This Means For You

The variants of COVID-19 that are circulating around the world, as well as the waning of vaccine-induced immunity with time, have motivated vaccine manufacturers to produce booster shots to help prevent severe illness. It's recommended that you receive boosters for continued protection.

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.

8 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 takes additional actions on the use of a booster dose for COVID-19 vaccines.

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

  3. Food and Drug Administration. Coronavirus (COVID-19) update: FDA expands eligibility for Pfizer-BioNTech COVID-19 vaccine booster dose to children 5 through 11 years.

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

  5. Centers for Disease Control and Prevention. COVID-19 vaccines for moderately or severely immunocompromised people.

  6. Food and Drug Administration. Coronavirus (COVID-19) update: FDA authorizes second booster dose of two COVID-19 vaccines for older and immunocompromised individuals.

  7. Moderna. Moderna announces new supply agreement with Israel for 2022.

  8. Centers for Disease Control and Prevention. SARS-CoV-2 variant classifications and definitions.

By Valerie DeBenedette
Valerie DeBenedette has over 30 years' experience writing about health and medicine. She is the former managing editor of Drug Topics magazine.