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

Over 80% of the United States population has received at least a single dose of one of the COVID-19 vaccines authorized by the Food and Drug Administration (FDA).

COVID-19 vaccines first became available in December 2020. Like most vaccines, the COVID-19 vaccines work in more than one way to prevent infection. The first involves the production of antibodies.

Your body uses antibodies to fight off infection, but not as easily when it has never seen a novel, or new, virus. Because SARS‑CoV‑2 was a new virus, human bodies had not developed an antibody defense for it. The vaccines help it to achieve that.

The second way the vaccines work is to help the body develop responses in what are called memory B cells and T cells. These are immune cells that store information for future reference. This ability is called immunological memory.

However, immunity does wane. Your individual response and other factors contribute to this loss of protection. Like human memory, cellular memory is short. Booster shots help to “remind” it of how to respond to a virus or other pathogen.

That said, to help maintain immunity, COVID-19 boosters and updated vaccines have been rolled out each fall since 2021.

This article explores research on the vaccines and what is known about the immunity they provide. It will help you to know more about each specific vaccine and how often you will need to get them. Here’s how each of the current vaccines works.

Pfizer-BioNTech Vaccine

Pfizer-BioNTech is an mRNA vaccine, based on a newer approach to making vaccines. It relies on the power of nucleic acids found in genetic material, but not the DNA that is uniquely yours. Here’s what is known about how long it will work to offer immunity.

Pfizer’s vaccine, also known as Comirnaty, was authorized for emergency use in the U.S. in December 2020. In August 2021, it received full approval from the FDA for use in individuals ages 16 and older. It was later authorized for anyone ages 6 months and older.

Since then, Pfizer has updated the formula of the vaccine to provide better protection against newer variants of the virus, like Omicron and its subvariants.

When Does It Start Working?

The original Pfizer vaccine was given in two doses scheduled three weeks apart. With the current updated formula, the vaccine is given as a single dose for anyone 5 years and older. For those who are immunocompromised and for children up to 4 years old, the vaccine is given as a three-dose series. However, for those receiving multiple doses for their initial vaccination, an interval longer than four weeks between doses may help reduce the risk of myocarditis associated with the mRNA COVID-19 vaccines.

According to the CDC, these doses are given as injections and offer full protection two weeks after the second dose. The data suggest that after the first dose, some immune response is present in about two weeks.

How Long Does Immunity Last?

According to results reported by Pfizer in April 2021 based on Phase 3 clinical trials in adults, the original vaccine was 91% effective in providing immunity against COVID-19 for six months. A November 2021 update focused on how effective the vaccine was in people ages 12 to 15, over a period of four months. These results showed the vaccine was 100% effective against COVID-19.

Further research on the Pfizer vaccine supports its effectiveness. A November 2021 research review of studies on nine different COVID-19 vaccines developed around the world found that overall, the Pfizer and Moderna vaccines performed better than alternatives in preventing symptomatic disease.

Boosters and Updated Vaccines

In November 2021, the FDA approved a single booster shot of the Pfizer COVID-19 vaccine for people aged 18 and older. The FDA later expanded that authorization to include children and adolescents ages 5 to 17 who completed their initial vaccination series at least five months prior. Additional mRNA booster doses for certain higher-risk individuals were also recommended.

The vaccine’s formula has been updated and authorized every year to more closely match the dominant COVID-19 variant. The 2024-2025 formula authorized in August 2024 targets the KP.2 Omicron variant.

Moderna Vaccines

The Moderna vaccine, also known as Spikevax, has been FDA-approved for use in the U.S. since January 2022 for the prevention of COVID-19 in individuals 18 years of age and older. Prior to this approval, it had been authorized for emergency use in the U.S. since December 2020. The vaccine was later authorized for use in individuals 6 months through 17 years of age. Like Pfizer, it is an mRNA vaccine but there are a few differences.

Moderna has since updated the formula of its vaccine to provide better protection against newer variants of the virus.

When Does It Start Working?

The Moderna vaccine was also originally given in two doses. Both are needed to be considered fully vaccinated. People who receive this vaccine need to schedule their second dose four weeks after the first—and no sooner.

As with the Pfizer vaccine, the CDC states that an eight-week interval between doses may be optimal for certain people to reduce the risk of myocarditis.

Full protection is achieved two weeks after the second dose, but some protection occurs earlier. A document filed with the FDA shows an overall efficacy of 50.8% between days one and 14. That rises to 92.1% after 14 days when you’ve had one dose but are still waiting for the other.

How Long Will Immunity Last?

Correspondence in The New England Journal of Medicine (NEJM) states that antibodies produced in response to Moderna’s original COVID-19 vaccine persisted through six months after the second dose.

According to the CDC, updated COVID-19 vaccines can provide protection for several months.

Boosters and Updated Vaccines

On November 19, 2021, the FDA approved a single booster shot of the Moderna COVID-19 vaccine for those aged 18 and older.

A second mRNA booster was later authorized for people 12 years and older with certain kinds of immunocompromise and all adults 50 and older who have received an initial booster at least four months previously.

Like the Pfizer vaccine, the formula of the Moderna vaccine has been updated to help protect against newer variants. The updated 2024-2025 formula targets the KP.2 Omicron variant.

Novavax Vaccines

The Novavax COVID-19 vaccine is a protein subunit vaccine, which means it contains pieces of the virus that causes COVID-19. On August 19, 2022, the FDA authorized the Novavax COVID-19 Vaccine, Adjuvanted for emergency use in individuals ages 12 and older.

As with the mRNA vaccines, the Novavax vaccine has been updated annually to match newer variants. In October 2023, the FDA authorized Novavax’s updated vaccine formula, which was designed to protect against the XBB.1.5 Omicron variant. In August 2024, Novavax updated the formula to target the JN.1 Omicron variant, which is the parent strain of the KP.2 strain that the updated mRNA vaccines target.

How Long Will Immunity Last?

Research suggests that the Novavax vaccine is just as safe and effective as the Pfizer-BioNTech and Moderna COVID-19 vaccines. It was associated with protection against infection with the Omicron variant and symptomatic COVID-19 up to four months after completing the primary series.

Effectiveness Against New Strains

The COVID-19 virus has changed over time due to mutations that result in a different strain of the virus. This is common for viruses, but some changes have greater impact than others. They may spread more rapidly, cause more or less serious illness, or fail to respond to the existing vaccines.

The CDC will classify some strains as a “variant of concern” when they have the potential for this greater impact. In late 2021, the Omicron became the dominant variant and was considered a variant of concern. Omicron subvariants remain the dominant strain of the virus.

Omicron and Vaccines

Because the Omicron variant was newly emerging and spreading quickly, there is little data to support a conclusion about how vaccines will provide immunity. In a December 2021 update, the CDC said it fully expected breakthrough infections even among the fully vaccinated.

Early evidence suggested that vaccinated people can still spread the Omicron variant. However, the existing vaccines were still expected to protect against serious illness and death.

Since then, both the 2023-2024 and 2024-2025 formulas of each vaccine have targeted Omicron subvariants. One study found that people who received the updated 2023-2024 vaccine were less likely to be hospitalized from COVID-19 than those who did not receive it.

Summary

The short answer to how long your COVID-19 vaccine will protect you is that no one knows for sure yet. The FDA is clear that there is not yet enough data to definitively answer the question. However, for many people, vaccination can provide months of protection.

Years after the pandemic started, there has been much progress. The three updated vaccines that are currently authorized for use in the U.S. (Pfizer, Moderna, and Novavax) continue to protect people from becoming seriously ill in the hospital or dying from the disease.

Just as the virus changes over time, so does the global response to it. If you’re still not sure about the vaccines, consider the CDC’s advice: Any vaccine is better than none at all.

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.