Developed by Massachusetts-based biotechnology company Moderna Therapeutics, this COVID-19 vaccine was authorized for emergency use by the U.S. Food and Drug Administration on December 18, 2020.

Important Information about the Moderna Vaccine

  • Number of doses required: 2 doses of the same vaccine
  • Time between dose: Minimum of 28 days
  • Authorized for: People age 18 and up
  • How long before protection begins: 2 weeks after second dose
  • Effectiveness: 95 percent
  • How long protection will last: Unknown at this time; study is ongoing
  • Storage: Freezing temperatures typical of a normal freezer

There has not yet been enough testing of the vaccine in children or pregnant or breastfeeding women to provide sufficient data about the vaccine in those groups. However, more studies are expected in these groups.

While children under the age of 18 are not eligible to receive the Moderna vaccine at this time, pregnant women can receive it. They should talk to their healthcare provider about the vaccine.

How the Moderna Vaccine Works

Both the Moderna and Pfizer COVID 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.

How the Vaccines Were Developed

Although both vaccines were developed quickly, they both underwent the same rigorous approval process as laid out by the FDA. Learn more about the vaccines' development and approval process.

In September, University of Maryland School of Medicine became one of the clinical research sites working on phase three testing of this vaccine. A key focus of this trial was to include people most impacted by COVID-19, including those from the African American and Latino communities. Learn more about how we're fighting COVID at the University of Maryland Medical System.

Special Considerations

Side Effects of the Moderna Vaccine

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

Reactions at the injection site, including:

  • Pain
  • Swelling (hardness)
  • Redness
  • Tenderness and swelling of the lymph nodes in the same arm of the injection

General side effects:

  • Fatigue
  • Headache
  • Muscle and/or joint pain
  • Chills
  • Nausea and vomiting
  • Fever

Possible Allergic Reactions to the Moderna Vaccine

While severe allergic reactions have been extremely rare, there is a slight risk of an allergic reaction to the Moderna 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

If you have a history of severe allergic reactions, talk to your doctor before receiving the vaccine and tell your vaccine provider about your history of allergies. 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 FDA fact sheet for information on vaccine ingredients for Moderna.

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 1/7/2021


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