How Long Will COVID-19 Vaccine-Induced Immunity Last?

Older woman receiving a vaccine shot in the arm.

Luis Alvarez / Getty Images

Key Takeaways

  • The Moderna and Pfizer-BioNTech vaccines offer immunity against COVID-19 for at least six months and might offer protection for up to two to three years. However, they will most likely have to be administered annually.
  • The Johnson & Johnson, Moderna, and Pfizer-BioNTech vaccines will likely protect against current variants of COVID-19.
  • Immunity wanes as antibody levels drop in response to a lack of use.
  • Moderna and Pfizer-BioNTech have launched preliminary studies of booster shots.

As of April 26, 2021, COVID-19 vaccines had been administered to more than 140 million people in the United States, according to the Centers for Disease Control and Prevention (CDC). Moderna and Pfizer-BioNTech's vaccines offer immunity with effectiveness in clinical trials of 94% and 95% (91% for up to six months) respectively. Johnson & Johnson's COVID-19 vaccine also offers immunity with about 66% percent effectiveness at preventing moderate to severe disease and 85% effectiveness at preventing severe disease. But the exact duration of the immunity for the vaccines is still unknown.

Will it last years or months? While experts say that only time—and further research—will tell, some are inclined to believe that COVID-19 vaccinations will be a recurring, rather than a one-off, event. 

What This Means For You

While more research needs to be done, experts believe you may have to receive the COVID-19 vaccine multiple times throughout your life rather than just once. The vaccines may need to be distributed annually.

When Does It Start Working?

After receiving a COVID-19 vaccine, it takes weeks for your immunity to build. According to the CDC, full protection occurs two weeks after the second dose of the Pfizer-BioNTech or Moderna COVID-19 vaccines, or two weeks after the single-dose Johnson & Johnson vaccine.

Although it takes a second dose to reach full protection for the Pfizer-BioNTech and Moderna vaccines, data suggests that a significant immune response occurs about two weeks after the first dose. For example, an FDA briefing document for Moderna's emergency use authorization application listed an overall efficacy of 50.8% between days one to 14 and an efficacy of 92.1% occurring after 14 days for one dose.

A CDC report that tracked almost 4,000 healthcare personnel, first responders, and other frontline workers under real-world conditions found that the mRNA vaccines (Pfizer-BioNTech and Moderna) were 80% effective at least 14 days following the first dose and 90% effective at least two weeks after the second dose.

How Long Will Immunity Last?

It “is very likely that for [the] COVID-19 vaccine, given that the length of immunity the vaccine generates is limited, we may have to be vaccinated annually,” Chunhuei Chi, ScD, MPH, director of the Center for Global Health at Oregon State University’s College of Public Health and Human Sciences, tells Verywell.

In this regard, the COVID-19 vaccines currently available are not unusual. Most vaccines, Chi says, “have their specific duration of immunity that can range from a few months to decades.” The flu vaccine, which immunizes against seasonal influenza for several months, represents one end of the spectrum; the measles vaccine, which immunizes against measles for life, represents the other. The magnitude of variation, Chi says, is the result of the unique “combination of characteristics of viruses and vaccines.”

The hope, Jere McBride, PhD, director of the experimental pathology graduate program at the University of Texas Medical Branch, tells Verywell, is that the Moderna and Pfizer-BioNTech vaccines will confer immunity for two to three years. In reality, however, the duration “could be longer or shorter” and will only be determined by conducting studies of people who have received the vaccine.

On April 1, 2021, Pfizer announced that an updated analysis of its Phase 3 trial showed that the vaccine was 91% percent effective overall and 100% effective in preventing severe disease (as defined by the CDC) for up to six months.

Correspondence in the New England Journal of Medicine (NEJM) also stated that Moderna was found to offer strong antibody protection for at least six months following the second dose.

McBride does not anticipate the discovery of differences in immunity duration between the two mRNA vaccines because the two work in similar ways. “The Moderna and Pfizer vaccines should be similar, based on the mRNA approach and the fact that the specific mRNA used to induce immunity is similar,” he says.

Like most vaccines, the COVID-19 vaccines have multiple mechanisms for preventing infection. The first involves the production of antibodies; the second involves the induction of responses in memory B and T cells—immune cells that retain information for future reference.

However, immunity does wane. When it does so often varies between individuals based "on how they immunologically respond to a vaccine," McBride says. Like human memory, cellular memory is short. The purpose of a booster shot is to jog it.

Booster Shots

On February 25, 2021, Pfizer announced that it is studying a third dose of its COVID-19 vaccine in a group of participants from its trials in order to understand the safety and tolerability of booster vaccines. The company is also in discussions with regulatory authorities about conducting a study using a vaccine targeting COVID-19 variants.

On March 10, 2021, Moderna announced the launch of a booster study targeting the B.1.351 variant that was first identified in South Africa.

Effectiveness Against New Strains

In December 2020, the news that scientists had discovered a new—and possibly more contagious—strain of COVID-19 cast a shadow over the vaccines’ rollout. First identified in southeastern England in September, the new strain B.1.1.7 has since spread to multiple countries, including the United States.

But McBride says the original and the mutant are similar enough that the vaccines should immunize against both. 

“Although new coronavirus strains emerge, the variation is not as large as that seen with seasonal influenza strains, and whether it affects vaccine efficacy is dependent on where the mutation occurs," he says. "In this case, the vaccine will likely protect against the variant as well."

By late January, additional variants B.1.351 first identified in South Africa and P.1 first identified in Brazil were also identified in the United States.

Overall, studies suggest that antibodies generated from the three authorized vaccines offer protection from these variants, but research is ongoing to try to understand if protection is lowered or if booster shots may be needed.

Lab studies of the Moderna vaccine suggest protection against variants, including B.1.1.7 first found in the United Kingdom, yet the protection may not be as robust against B.1.429 first found in California and particularly B.1.351 first found in South Africa.

Correspondence published in NEJM on March 8, 2021, also suggests that the Pfizer-BioNTech vaccine may offer protection from multiple variants. Researchers described a preliminary lab study that used live virus and blood samples collected from people who had received two doses of the vaccine. The researchers found protection from the B.1.1.7. variant first found in the United Kingdom, and the P.1. variant first found in Brazil. There was also protection against the B.1.351 variant first found in South Africa, but it was not as robust as the others. The researchers caution that real-world evidence is still needed.

On April 1, 2021, Pfizer announced that the updated analysis of its Phase 3 trial showed that the vaccine offered immunity in South Africa where the B.1.351 variant is prevalent.

The Johnson & Johnson clinical trial, which was conducted while COVID-19 variants were spreading, found that the overall efficacy in its South Africa trial was lower (64%) than in other trial locations, such as the United States (72%). However, its protection against severe disease included the B.1.351 variant and other variants.

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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15 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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