Developed by Massachusetts-based biotechnology company Moderna Therapeutics, this COVID-19 vaccine was granted Emergency Use Authorization (EUA) by the U.S. Food and Drug Administration (FDA) on December 18, 2020 for use in individuals ages 18 and older.

  • In August 2021, the EUA was expanded to include a third dose of Moderna for moderately to severely immunocompromised people ages 18 and up. That EUA is still in effect.
  • In October 2021, the CDC recommended a booster shot for certain individuals who initially received the Moderna vaccine. The new CDC booster guidance 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 Moderna Vaccine

  • Number of doses required: 2 doses of the same vaccine
  • Time between doses: Minimum of 28 days
  • Time to reach full protection: 14 days after second dose
  • Booster shots available: Yes, five months after your second dose for people ages 18 and older. See CDC booster recommendations.
  • Third dose for immunocompromised people: Yes, at least 28 days after the second dose
  • FDA status: Ages 18 and up, booster dose for certain individuals and third dose for immunocompromised people (FDA EUA)
  • Effectiveness: Highly effective in preventing severe illness, hospitalization and death
  • Storage: Freezer (-13 to 5 degrees Fahrenheit)

How the Moderna Vaccine Works

Both the Moderna and Pfizer (Comirnaty) 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 Moderna Vaccine

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

  • Children under the age of 18 are not eligible to receive the Moderna vaccine at this time; studies are under way to test its safety and effectiveness in children.
  • People who are allergic to any of the vaccine's ingredients or those who had an allergic reaction to their first dose cannot receive this vaccine. Please see additional information about allergic reactions below.

Moderna 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 18 and up who are moderately to severely immunocompromised and who received the Moderna 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 Moderna Vaccine Was Developed

Although the Moderna 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 September 2020, 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.

Allergic Reactions and Side Effects

Please see the FDA's Fact Sheet for the Moderna vaccine or 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 (see additional information above)
  • 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 1/10/2022

UMMS provides our expert-reviewed content to keep our community informed. When sharing this copyrighted content, please link to our site so that critical updates are reflected.