Here's Why You'll Probably 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.
  • Booster shots help immunize against the variants of the SARS-CoV-2 virus while also increasing immunity as protection from the original shot wanes.
  • 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.

More than 75% of U.S. adults have now received at least one dose of the three available COVID-19 vaccines. But with the rise of virus variants and the potential for waning vaccine-induced immunity, experts are saying even the fully vaccinated may soon need booster shots.

Variants Driving Need for Boosters

Several variants of SARS-CoV-2, the virus that causes COVID-19, are circulating in the U.S. Some, notably the Beta variant (B.1.351), have mutations that appear to reduce the effectiveness of the COVID-19 vaccines that are currently available.

Vaccine makers have already addressed the immunological challenge posed by variants. 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.

The the Centers for Disease Control and prevention (CDC) now recommends a single booster dose to be administered at least six months after completion of the primary Pfizer or Moderna series in those who are:

Those 18 years and older who received the Johnson & Johnson vaccine are eligible for a booster at least two months after getting the initial vaccination.

According to the CDC, eligible individuals are able to choose any authorized COVID-19 booster—regardless of vaccine type that was used for the initial vaccination. 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 that shows increased resistance to antibodies created by previous infection or vaccination or in which prior treatment methods are not as effective. 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 for previous variants are not effective.

Some notable variants being monitored in the U.S. include:

  • Alpha: This variant was first detected in Britain. It was identified in the U.S. in December 2020. It is more easily transmissible and appears to cause more severe disease than the original virus.
  • Beta: This variant was first identified in South Africa in December 2020 and has been known to be in the U.S. since the end of January 2021. It is more easily transmissible than the original virus, and the current vaccines may be less effective against it.
  • Gamma: This variant was initially identified in Brazil and Japan in early January. It was first detected in the U.S. in January 2021.
  • Epsilon: These two variants were first identified in California in February 2021. These are slightly more transmissible than the original virus.

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

In March, Moderna shipped supplies of a booster vaccine against the Beta variant to the National Institutes of Health (NIH) for phase 1 clinical trials and reports that its own phase 2 clinical trials on the boosters are already underway.

According to the CDC, the Beta variant, first identified in South Africa, spread to several states. It is more easily transmissible than the original forms of the virus.

During a press conference held by Johns Hopkins, Anna Durbin, MD, professor in the department of international health at Johns Hopkins Bloomberg School of Public Health, explained that “most of the [vaccine] companies are in fact developing and testing booster shots of their vaccines and importantly I think, to note, is that this booster will likely cover the most extreme variant that we know of, the South African variant.”

Waning Immunity

Because immunity created by most vaccines wanes with time, booster shots will likely be 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 the 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 ten years and older adults need a pneumococcal vaccine every five 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, motivated vaccine manufacturers to work on booster shots. It’s likely that at some point, even if you’ve been fully vaccinated, you’ll need to get a third dose to ensure lasting 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.

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6 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.
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  2. Wang P, Nair MS, Liu L, et al. Antibody resistance of SARS-CoV-2 variants B.1.351 and B.1.1.7. Nature. 2021;593(7857):130-135. doi:10.1038/s41586-021-03398-2

  3. Food and Drug Administration. Coronavirus (COVID-19) update: FDA takes additional actions on the use of a booster dose for COVID-19 vaccines. Published October 20, 2021.

  4. Centers for Disease Control and Prevention. CDC expands eligibility for COVID-19 booster shots. Published October 21, 2021.

  5. Moderna. Moderna announces new supply agreement with Israel for 2022. Published April 20, 2021.

  6. Centers For Disease Control and Prevention. SARS-CoV-2 variant classifications and definitions. Updated October 4, 2021.