To slow the spread of the unprecedented COVID-19 pandemic, groundbreaking vaccines have been developed to protect people from the SARS-CoV-2 virus that causes COVID-19.

There are currently three different vaccines approved by the Food and Drug Administration (FDA) for use in the United States:

Additional vaccines not yet approved for use in the United States include:

Many people are concerned about just how long the vaccines will last — whether they offer lifelong protection, like the mumps vaccine, or they’ll need occasional boosters, like the flu vaccine.

The answer to this question is not simple and is still being investigated, with many factors, like number of participants, timing of studies, and participant health, all affecting research outcomes.

But data is increasingly demonstrating more detailed efficacy numbers for all five of the vaccines that are being administered around the world.

Here’s a look at what data says about how long the most widely administered COVID-19 vaccines last.

ModernaPfizer-BioNTechJohnson & JohnsonOxford-AstraZenecaNovavax
How long it lastsabout 6 monthsabout 6 monthsabout 8 monthsabout 3 monthsabout 6 months
Efficacy94.1%95%66.3%77%89.7%
Dosestwo, 28 days aparttwo, 21 days apartonetwo, 4–12 weeks aparttwo, 21 days apart
Immunity2 weeks after second dose2 weeks after second dose2 weeks after single dose15 days after second dose2 weeks after second dose
TypemRNAmRNAadenovirus vectoradenovirus vectorprotein adjuvant

Knowing how long the vaccine you received will provide protection can help you feel more confident in making long-term plans, such as returning to a physical workspace or classroom, as well as attending public events.

Moderna (mRNA-1273)

The Moderna vaccine was approved for use in the United States on December 18, 2020. It’s also been approved for use in many other countries and throughout the European Union.

The Moderna vaccine is recommended for people 12 years and older, having received FDA emergency use authorization (EUA) for 12 to 17-year-olds in August 2021.

Here are some key facts and figures about the Moderna vaccine and how effective it is, according to the latest research.

Moderna: Key efficacy facts

  • Efficacy: Studies have suggested the Moderna vaccine is about 94.1 percent effective at preventing COVID-19.
  • How long immunity lasts: Studies have suggested immunity will likely last at least 6 months.
  • Protection against variants: Moderna found in May 2021 that a booster shot of the vaccine after a second dose is effective against the Beta and Gamma variants. A preprint study published in August 2021 found that Moderna was up to 85 percent effective against the Delta variant.
  • How it works: The Moderna vaccine is a messenger RNA (mRNA) vaccine. Unlike traditional vaccines that inject a tiny inactive amount of a virus into a person, mRNA vaccines use a piece of genetic coding from the virus itself that enters your body and activates your immune response. This causes you to produce antibodies for the virus and gives your cells a memory of the virus that your body can use to fight off the actual virus if needed.
  • How many doses you need: Two doses, 28 days apart.
  • When you become immune: 2 weeks after your second dose.

Pfizer-BioNTech (Comirnaty)

The Pfizer-BioNTech vaccine was approved for use in the United States on December 11, 2020. It’s also available in the European Union under the name Comirnaty, and in many other countries worldwide. The vaccine is currently recommended for anyone over 12 years old.

Here are some key facts and figures about how effective the Pfizer-BioNTech vaccine is and how it works.

Pfizer-BioNTech: Key efficacy facts

  • Efficacy: Studies showed the vaccine is about 95 percent effective in preventing COVID-19.
  • How long immunity lasts: Studies suggested immunity will last at least 6 months.
  • Protection against variants: Research found that the vaccine is effective at preventing the Beta variant. A July 2021 study found that the vaccine was about 88 percent effective against the Delta variant and 93.7 percent effective against the Alpha variant.
  • How it works: Just like the Moderna vaccine, the Pfizer-BioNTech vaccine is an mRNA vaccine. It works by inserting a tiny piece of genetic material from the virus into your body. This teaches your body how to fight the virus and protects you from actual infection.
  • How many doses you need: Two doses, 21 days apart.
  • When you become immune: 2 weeks after your second dose.

Johnson & Johnson (Janssen)

The Johnson & Johnson vaccine was approved for use in the United States on February 27, 2021.

In April 2021, concerns about the vaccine causing blood clots caused a pause in distribution. But, on April 23, 2021, the FDA stated that the vaccine was still considered safe for most recipients and could continue being administered.

This vaccine is widely approved for use in adults 18 and older, including in the European Union under the name Janssen.

Here are some key facts and figures about the Johnson & Johnson vaccine’s efficacy and how it works.

Johnson & Johnson: Key efficacy facts

  • How effective it is: The vaccine has been shown to be about 66.3 percent effective against COVID-19. Studies have also shown that the vaccine is 85 percent effective against serious illness from COVID-19.
  • How long immunity lasts: Two pre-print studies released in July 2021 suggested that protection against COVID-19 will last at least 8 months.
  • Protection against variants: Early studies of the vaccine have shown it’s very likely it will be effective in protecting recipients from variants.
  • How it works: The vaccine is an adenovirus vector vaccine, using a lab-created inactive adenovirus (the virus that causes a cold) as a shell for spike proteins from the SARS-CoV-2 virus. When this shell virus enters your system, it enters your cells and teaches them how to fight COVID-19.
  • How many doses you need: One
  • When you become immune: 2 weeks after a single dose.

Oxford-AstraZeneca (Vaxzevria)

The Oxford-AstraZeneca vaccine isn’t approved for use in the United States, but it’s currently distributed in the United Kingdom, Canada, Australia, the European Union, and dozens of other countries worldwide.

In some countries, the vaccine is distributed under the name Vaxzevria. It’s recommended for adults 18 and older.

Here are some key facts and figures about how effective the Oxford-AstraZeneca vaccine is against COVID-19.

Oxford-AstraZeneca: Key efficacy facts

  • Efficacy: Trials found the vaccine to be 77 percent effective against COVID-19 and 100 percent effective against serious illness from the virus.
  • How long immunity lasts: Trials are still being done to determine how long immunity from this vaccine will last, but data suggests that efficacy declines by about 10 percent 90 days after the second dose.
  • Protection against variants: An April 2021 study found the vaccine is effective against the Alpha variant. An August 2021 pre-print study found the vaccine was at least 67 percent effective against the Delta variant.
  • How it works: The vaccine uses the same adenovirus vector technology as the Johnson & Johnson vaccine. A lab-created inactive adenovirus shell carries COVID-19 proteins. Once it’s in your body, the virus can’t reproduce and make you sick. Instead, it teaches your cells how to fight COVID-19.
  • How many doses you need: Two doses, 4 to 12 weeks apart.
  • When you become immune: 15 days after your second dose.

Novavax

The Novavax vaccine is still in clinical trials and hasn’t yet been approved for distribution in any country. When it’s approved, the vaccine will be recommended for people 12 and older.

Here are some key facts and figures on how effective the Novavax vaccine is expected to be.

Novavax: Key efficacy facts

  • Efficacy: This vaccine has been shown to be about 89.7 percent effective in preventing COVID-19 and 100 percent effective in preventing serious illness.
  • How long immunity lasts: Trials are still being done to determine how long immunity from this vaccine will last. An August 2021 statement from Novavax suggested that a booster shot given 6 months after the second dose provided immunity more than four times stronger than immunity after the first two doses.
  • Protection against variants: Trials have shown the vaccine to be 86.3 percent effective against the Alpha variant.
  • How it works: The Novavax vaccine is a protein adjuvant vaccine. Unlike an adenovirus vector or mRNA vaccine, this vaccine uses proteins from the SARS-CoV-2 made into nanoparticles. These particles can’t make you sick, but they can help train your body to fight COVID-19.
  • How many doses you need: Two doses, 21 days apart.
  • When you become immune: 2 weeks after your second dose.

All vaccines currently approved for use in the United States and elsewhere have been shown to be safe and effective in studies. Most side effects of the vaccines are mild and resolve within a day or two.

Ongoing research continues to determine just how long the vaccines will provide immunity. The Moderna and Pfizer-BioNTech vaccines appear to provide immunity for at least 6 months.

As time passes and more people get vaccinated, more, increasingly detailed data will become available.