Everything You Need to Know About the Moderna Vaccine

doctor extracting coronavirus vaccine

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Key Takeaways

  • The Moderna COVID-19 vaccine is the second vaccine to be granted emergency use authorization (EUA) in the United States, and it is awaiting full FDA approval.
  • Shots of this vaccine are currently available for people ages 18 and older, but Moderna has started clinical trials to study its use in children and teens.
  • The Food and Drug Administration (FDA) has authorized a booster dose of either the Pfizer-BioNTech or Moderna vaccine for all adults ages 18 and older. The CDC strongly recommends a booster if you are eligible for it.
  • Recent research suggests that Moderna's vaccine may offer more lasting protection than others.
  • The Moderna vaccine does not appear to have any serious risks for pregnant people and is recommended for use in pregnancy by top U.S. health organizations.

In December 2020, the Food and Drug Administration (FDA) authorized the Moderna COVID-19 vaccine for emergency use in people ages 18 and older. Moderna's vaccine followed Pfizer-BioNTech's as the second vaccine available in the U.S. to fight the coronavirus pandemic.

Though it's still awaiting full FDA approval, which has thus far been granted only to Pfizer's vaccine, the Moderna vaccine is recommended by the Centers for Disease Control and Prevention (CDC) to protect against COVID-19. It's widely available, and more than 150 million doses have been administered in the U.S. to date. Here’s everything your family needs to know about the Moderna vaccine. 

How Does It Compare to the Pfizer Vaccine?

Both vaccines are formulated with mRNA technology. Unlike other types of vaccines that trigger an immune response by injecting a weakened or inactivated germ into the body, an mRNA vaccine teaches our cells how to make their own immune response. It does this by encoding part of the spike protein found on the surface of the virus that causes COVID-19.

Both vaccines are administered in two doses—three weeks apart for the Pfizer vaccine and one month (28 days) apart for the Moderna vaccine. The FDA has authorized a third booster dose of either the Pfizer or Moderna vaccine for all people ages 18 and older. A booster dose, which should come six months after a second shot of either the Pfizer or Moderna vaccine or two months after a single-shot Johnson & Johnson (J&J) vaccine, is strongly recommended by the CDC for all eligible adults. Moderna boosters cleared by the FDA are given in a half-dose portion.

If you qualify for a COVID-19 booster dose, you can safely receive a different brand of FDA-authorized vaccine than the one you received for your earlier shots, according to the CDC. That means you can receive a Moderna booster even if you had the Pfizer or J&J vaccine previously, or you can get a Pfizer booster even if you started out with the Moderna or J&J vaccine. Be sure to talk to your doctor about whether "mixing and matching" vaccines may be a good idea for you.

Early clinical trials showed that both vaccines are highly effective against COVID-19, with Pfizer offering 95% protection and Moderna offering 94.1% protection. More recent data by the CDC suggests that the Moderna vaccine may provide more lasting protection against COVID-19. It showed that Moderna's vaccine remains 92% effective after 120 days, while the Pfizer vaccine's efficacy drops to 77% after that period.

Neither vaccine is quite as effective against the Delta variant predominating in late 2021, but preliminary data collected by researchers at the Mayo Clinic suggests Moderna's vaccine might provide slightly better protection than Pfizer's.

What About My Children?

Currently, the Moderna vaccine is only authorized for adults ages 18 and over. (The Pfizer vaccine can be given to people ages 12 and over). However, Moderna, like Pfizer, recently began clinical trials of the vaccine in younger children. There will be further FDA review before the vaccines are available for kids.

Until studies about children's reactions to COVID-19 immunization are completed, we won't know what dose of the COVID-19 vaccine they'll require, either. "Each vaccine can vary," says Danelle Fisher, MD, pediatrician and vice chair of pediatrics at Providence Saint John’s Health Center in Santa Monica, California.

Dr. Fisher points to the flu vaccine as one example—children under age 8 who are getting the vaccine for the first time need to get two doses, four weeks apart. Thereafter, they get one dose per year, just like adults do.

Danelle Fisher, MD

Get your children a flu vaccine if they haven’t gotten one yet. No one wants to have the flu plus COVID-19.

— Danelle Fisher, MD

Can I Get the Moderna Vaccine If I’m Pregnant or Breastfeeding?

The CDC and the American College of Obstetricians and Gynecologists (ACOG) recommend that people who are pregnant get vaccinated against COVID-19.

Pregnant people were not included in early clinical trials of the Moderna vaccine or any other COVID-19 vaccine. Moderna is now performing clinical trials to look at the vaccine's safety and effectiveness in pregnant people, specifically.

A preliminary study published in the New England Journal of Medicine did find that the Moderna vaccine does not pose a serious risk for pregnant people. The findings were based on the CDC's V-safe smartphone-based surveillance system and the CDC's Vaccine Adverse Event Reporting System (VAERS), which included data from 35,691 pregnant people who had received an mRNA vaccine.

In a practice advisory, ACOG recommends that people who are breastfeeding also receive a COVID-19 vaccine. Recent research suggests that breastfeeding people who have received an mRNA vaccine like Moderna's have antibodies in their breast milk, which may provide added COVID-19 protection for the baby.

What to Expect When You Get the Vaccine 

In an FDA briefing document regarding Moderna's COVID-19 vaccine, the following symptoms are listed as potential side effects:

  • Injection site pain, swelling, or redness
  • Tiredness
  • Headache
  • Muscle pain
  • Joint pain
  • Chills
  • Fever
  • Nausea and/or vomiting

It's possible that children might experience different side effects, says Dr. Fisher. "I would be curious to know about gastrointestinal side effects such as abdominal pain or diarrhea," she says. "Both of those symptoms can be more prevalent in children than adults who get COVID-19. I do hope the rate of side effects is low and that they are mild in nature."

What This Means For You

If you are at least 18 years old, you are eligible for the Moderna vaccine, which research has shown to provide safe and ample protection against COVID-19, including the Delta variant. The vaccine is recommended for pregnant and breastfeeding people, and booster doses are available for adults ages 18 and older. It's crucial to continue to follow other COVID-19 safety measures, like wearing a face mask in indoor public spaces and keeping social distance in crowded settings. When you do socialize, gather outside as much as possible.

The information in this article is current as of the date listed, which means newer information may be available when you read this. For the most recent updates on COVID-19, visit our coronavirus news page.

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16 Sources
Verywell Family uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. U.S. Food & Drug Administration. Coronavirus (COVID-19) update: FDA expands eligibility for COVID-19 vaccine boosters. Published November 19, 2021.

  2. Centers for Disease Control and Prevention. CDC expands eligibility for COVID-19 booster shots to all adults. Published November 19. 2021.

  3. Centers for Disease Control and Prevention. Comparative effectiveness of Moderna, Pfizer-BioNTech, and Janssen (Johnson & Johnson) vaccines in preventing COVID-19 hospitalizations among adults without immunocompromising conditions—United States, March-August 2021. MMWR Morb Mortal Wkly Rep. 2021;70:1337-1343. doi:10.15585/mmwr.mm7038e1

  4. Shimabukuro TT, Kim SY, Myers TR, et al. Preliminary findings of mRNA COVID-19 vaccine safety in pregnant personsN Engl J Med. 2021;384:2273-2282. doi:10.1056/NEJMoa2104983

  5. Centers for Disease Control and Prevention. COVID-19 vaccines while pregnant or breastfeeding. Updated August 11, 2021.

  6. American College of Obstetricians and Gynecologists. COVID-19 vaccination considerations for obstetric-gynecologic care. Updated July 30, 2021.

  7. Centers for Disease Control and Prevention. COVID-19 Vaccinations in the United States. Updated September 27, 2021.

  8. Centers for Disease Control and Prevention. Understanding mRNA COVID-19 vaccines. Updated March 4, 2021.

  9. U.S. Food and Drug Administration. Coronavirus (COVID-19) update: FDA takes additional actions on the use of a booster dose for COVID-19 vaccines. Published October 20, 2021.

  10. Centers for Disease Control and Prevention. CDC expands eligibility for COVID-19 booster shots. Published October 21, 2021.

    1. U.S. Food & Drug Administration. Pfizer-BioNTech COVID-19 vaccine frequently asked questions. Updated August 23, 2021.
  11. U.S. Food and Drug Administration. Moderna COVID-19 Vaccine EUA Fact Sheet for Healthcare Providers. Updated August 27, 2021.

  12. Puranik A, Lenehan PJ, Silvert E, et al. Comparison of two highly-effective MRNA vaccines for COVID-19 during periods of Alpha and Delta variant prevalence. Pub Glob Health. 2021. doi:10.1101/2021.08.06.21261707

  13. Centers for Disease Control and Prevention. Flu & young children. Updated October 15, 2020.

  14. American College of Obstetricians and Gynecologists. Statement of strong medical consensus for vaccination of pregnant individuals against COVID-19. Updated September 14, 2021.

  15. Jakuszko K, Koscielska-Kasprzak K, Zabinska M, et al. Immune response to vaccination against COVID-19 in breastfeeding health workers. Vaccines. 2021;9(6):663. doi:10.3390/vaccines9060663