Developed by American pharmaceutical company Pfizer and German firm BioNTech, this COVID-19 vaccine was authorized for emergency use by the U. S. Food and Drug Administration on December 11, 2020. The Pfizer vaccine was the first COVID-19 vaccine made available in the United States.

Important Information about the Pfizer Vaccine

  • Number of doses required: 2 doses of the same vaccine
  • Time between doses: Minimum of 21 days
  • Authorized for: People age 16 and up
  • Time to reach full protection: 14 days after second dose
  • Effectiveness: Nearly 100% effective in preventing hospitalization and death
  • How long protection will last: Unknown at this time; studies are ongoing
  • 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 will be able to get the Pfizer vaccine or any of the other approved vaccines when it's their turn and they are eligible. However, a few groups of people cannot receive it or should consult a doctor first.

  • Children under the age of 16 are not eligible to receive the Pfizer vaccine at this time; studies are underway to test its safety and effectiveness in children.
  • Pregnant women, as well as those who are breastfeeding or may become pregnant, may receive the Pfizer vaccine. However, they should talk to their doctor first because clinical testing in this group has not been completed.
  • People who 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.

How the Pfizer Vaccine Was Developed

Although the vaccine was developed in less than a year, they went through 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.

Special Considerations

Side Effects of the Pfizer Vaccine

Possible side effects, which usually go away within 24-48 hours after receiving the vaccine, include:

  • Pain, swelling and/or redness at the injection site
  • Fatigue and/or feeling unwell
  • Headache
  • Joint and muscle pain
  • Chills and/or fever
  • Nausea
  • Swollen lymph nodes

Possible Allergic Reactions to the Pfizer Vaccine

While severe allergic reactions have been extremely rare, there is a slight risk of an allergic reaction to the Pfizer vaccine. Signs of an allergic reaction may include:

  • Difficulty breathing
  • Swelling of your face and throat
  • A fast heartbeat
  • A bad rash all over your body
  • Dizziness and weakness

Any immediate allergic reaction to another vaccine or injectable medicine, no matter how severe, is considered a precaution by the Centers for Disease Control and Prevention (CDC). In other words, you may be at higher risk of having a reaction to the vaccine.

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.

If you have a severe allergic reaction to the first dose of this vaccine, you should not receive the second dose. If you are allergic to any ingredient of the vaccine, you should not receive the vaccine.

Please see the Food and Drug Administration EUA Fact Sheet for information on vaccine ingredients for Pfizer.

The vaccine does not contain any egg-based technology, so there is no concern for people with egg allergies like there may be with other vaccines.

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
  • Are pregnant or plan to become pregnant
  • Are breastfeeding
  • Have received another COVID-19 vaccine

Updated 3/5/2021

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