Developed by American pharmaceutical company Pfizer and German firm BioNTech, this COVID-19 vaccine was granted full approval by the U. S. Food and Drug Administration (FDA) for people ages 16 and older. The approved vaccine has been given the brand name Comirnaty.

The Pfizer COVID-19 vaccine continues to be available under Emergency Use Authorization (EUA) for other groups of people.

  • The distribution of this vaccine began in December 2020 under FDA EUA that made the vaccine available for people ages 16 and up.
  • In May 2021, the EUA was expanded to include children ages 12 to 15. That EUA is still in effect, and this age group is still able to receive the vaccine.
  • On August 23, 2021, the Pfizer vaccine received full FDA approval for people ages 16 and up.
  • In August 2021, the EUA was expanded to include a third dose for moderately to severely immunocompromised people ages 12 and up. That EUA is still in effect.
  • In September 2021, the CDC recommended a booster shot of the Pfizer vaccine for certain individuals.
  • In October 2021, the CDC expanded its booster recommendations, including new guidance that allows eligible people to choose which vaccine they receive for their booster, regardless of which vaccine they received for their initial vaccination.

Important Information about the Pfizer Vaccine

  • Number of doses required: 2 doses of the same vaccine
  • Time between doses: Minimum of 21 days
  • Time to reach full protection: 14 days after second dose
  • Booster shots available: Yes, for certain people 
  • Third dose for immunocompromised people: Yes, at least 28 days after the second dose
  • FDA status: Ages 16 and up (FDA-approved); ages 5-15, booster dose for certain individuals and third dose for immunocompromised people (FDA EUA)
  • Effectiveness: Highly effective in preventing severe illness, hospitalization and death
  • Storage: Ultracold temperature as low as -112 degrees Fahrenheit

How the Pfizer Vaccine Works

Both the Pfizer and Moderna COVID-19 vaccines are based on messenger RNA (mRNA) technology. mRNA vaccines contain a code that provides the cells "instructions" to create antibodies to protect against COVID-19. Learn more about how mRNA vaccines work.

This type of vaccine does not contain any part of the virus, so it cannot cause COVID-19.

Who Can and Cannot Get the Pfizer Vaccine

The vast majority of people are able to get the Pfizer vaccine or any of the other approved vaccines. However, some people cannot receive it or should consult a doctor first.

  • Children under the age of 5 are not eligible to receive the Pfizer vaccine at this time; studies are underway to test its safety and effectiveness in children.
  • People who are allergic to any of its ingredients or had an allergic reaction to their first dose cannot receive this vaccine. Please see additional information about allergic reactions below.

Pfizer Booster Shot

The CDC recommends a booster shot for certain individuals.

The vaccine remains effective at protecting against severe illness, hospitalization and death from COVID-19, including against the Delta variant.

Public health experts have started to see some reduced protection among certain people, such as those who are older (65 years and older), work in high-risk settings or have underlying medical conditions that put them at higher risk for severe COVID-19.

A booster shot is only approved for people who are who are at least 18 years old and who:

  • Received their second dose of the Pfizer or Moderna vaccine at least six months ago and are eligible based on the CDC's criteria
  • Received the single-dose Johnson & Johnson vaccine at least two months ago

Regardless of the vaccine initially received, people eligible for a booster may choose any of the three vaccines available in the United States (Pfizer, Moderna or Johnson & Johnson).

Third Dose for Immunocompromised People

In August 2021, both the FDA and the CDC recommended a third dose of the mRNA vaccines (Pfizer and Moderna) for moderately to severely immunocompromised people to be given at least 28 days after their second dose of the vaccine.

The third dose must be the same vaccine type as the initial two-dose series. Individuals ages 12 and up who are moderately to severely immunocompromised and who received the Pfizer vaccine in their initial series may be eligible for a third dose.

For more information, please see the CDC's recommendations for immunocompromised people.

How the Pfizer Vaccine Was Developed

Although the Pfizer vaccine was developed quickly, it still underwent the same rigorous approval process as laid out by the FDA. No safety steps were skipped. Learn more about the vaccines' development and approval process.

In May 2020, the University of Maryland School of Medicine (UMSOM) became the first in the United States to begin testing this COVID-19 vaccine candidate. Learn more about how we're fighting COVID at the University of Maryland Medical System.

Allergic Reactions and Side Effects

Please see the FDA's Fact Sheets for the Pfizer vaccine (for people ages 12 and older or people ages 5 to 11) for the most up-to-date information on:

  • Vaccine ingredients
  • Side effects and what to do about them
  • Possible allergic reactions

If you have a history of immediate or severe allergic reaction to anything – especially another vaccine or injectable medicine – it is strongly recommended you talk to your doctor before getting the vaccine. This is so your doctor can confirm it is safe for you to get the vaccine.

If you have a history of severe allergic reactions, you will also be monitored for 30 minutes after your vaccination.

Other Conditions

Before you get vaccinated, you should talk to your doctor if you:

  • Have any allergies
  • Have a fever
  • Have a bleeding disorder or are on a blood thinner
  • Are immunocompromised or are taking a medicine that affects your immune system
  • Have received another COVID-19 vaccine

Updated 11/11/2021


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Regardless of the vaccine initially received, anyone eligible for a booster may receive any of the three vaccines available in the United States (Pfizer, Moderna or Johnson & Johnson).
Regardless of the vaccine initially received, anyone eligible for a booster may receive any of the three vaccines available in the United States (Pfizer, Moderna or Johnson & Johnson).