Moderna’s COVID-19 Vaccine: What You Need to Know


Moderna’s COVID-19 vaccine, called mRNA-1273, was the second vaccine to receive emergency use authorization from the Food and Drug Administration (FDA).


Moderna, an American biotechnology company based in Cambridge, Massachusetts, began developing its vaccine in January 2020. The company worked with the National Institutes of Health (NIH) to finalize gene sequencing for the virus and began working on developing the vaccine soon after.

The first batch of the vaccine was developed in early February—just 25 days after the gene was sequenced. The first dose of the vaccine was given in March 2020 in a Phase 1 clinical trial, and those early trials showed promising results. By mid-year, Moderna received funding and fast-track regulatory allowances to help move development along.

While a vaccine initially wasn’t expected for 18 months or more, the new developments meant Moderna could deliver millions of doses much sooner. In August 2020, the U.S. government ordered 100 million doses of the vaccine—even though it hadn’t even been approved for use yet, and in November, results of the Phase 1 clinical trial were published.

In December, results from Phase 3 clinical trials were published and the U.S. ordered an additional 100 million doses. In February 2021, the U.S. ordered another 100 million doses, bringing the total to 300 million doses.

When Was Moderna’s Vaccine Officially Approved?

American health officials granted Moderna’s vaccine an emergency use authorization on December 18, 2020, for adults 18 and older, making it the second vaccine to receive the designation from U.S. health officials in one week.

How It Works

The Moderna vaccine is an mRNA vaccine, similar to the one developed by Pfizer. The technology behind these vaccines has been around for about three decades and shown promise in preventing notoriously difficult-to-prevent diseases—even cancer. Unlike conventional vaccines that use inactivated or live viruses, mRNA vaccines are non-infectious and contain no parts of the virus they fight. This makes mRNA vaccines safer for certain populations.

An mRNA (messenger ribonucleic acid) vaccine contains a single-stranded molecule that complements a strand of your DNA. These strands have a special coating that can protect mRNA from chemicals in the body that can break it down, and help it enter muscle cells.

Rather than exposing the body to a small amount of virus to create an immune response, mRNA causes the vaccine recipient to make the protein of interest. This includes:

  • Helping the cell make part of the spike protein that makes COVID-19 so potent
  • Teaching immune cells to recognize and fight similar spike proteins

According to the Centers for Disease Control and Prevention (CDC), mRNA vaccines teach our cells how to make a protein—or even just a piece of a protein. This triggers an immune response.

Moderna’s vaccine was initially tested in adults aged 18 to 55. The Phase 1 trial investigated three different doses—25, 100, and 250 micrograms—given twice, 28 days apart. By the Phase 3 trial, Moderna zeroed in on a two-dose formula of 100 micrograms each, given in two doses about four weeks apart.

How Was Moderna’s Vaccine Tested?

Moderna’s Phase 3 trial tested a two-dose vaccine (100 micrograms each, given 28 days apart) in adults ages 18 and older. The trial had more than 30,000 participants, including about 7,500 adults ages 65 and older and more than 5,000 adults ages 18 to 64 with risk factors for severe illness from COVID-19.

How Effective Is It?

Researchers that conducted the trials were able to test how effective the vaccine is in creating antibodies and neutralizing responses with tests that use bodily fluids like blood or urine to see whether antibodies to a particular virus can be found. These tests include:

  • ELISA (enzyme-linked immunosorbent assay) test
  • PsVNA (pseudotyped lentivirus reporter single-round-of-infection neutralization assay)
  • PRNT (plaque-reduction neutralization test)

Antibody levels from these tests were compared to those found in people who had recovered from COVID-19 infections. The study investigated responses by other immune cells, like T-cells, too.

After the first round of vaccinations in the 100-microgram and 250-microgram formulas in the Phase 1 trial, antibody responses were similar to the median level of immunity in those who had recovered from and had natural immunity after a COVID-19 infection.

Other immunity tests, like the PsVNA, showed little response after the first dose. However, after the second doses, antibody and other immune responses were strong among the vaccination group—reaching levels that were close to those with the highest natural immune responses after recovering from COVID-19.

Immune responses developed within about two weeks of the first dose, according to the trial report, but were much stronger after the second dose.

Exactly How Effective Is It?

Moderna’s vaccine has been shown in trials to be very effective—preventing COVID-19 in 94.1% of the people enrolled in the Phase 3 clinical trial. Additionally, the vaccine seems to have broad efficacy, with success rates consistent across various age, race, ethnicity, and gender groups.

The CDC also tracked almost 4,000 healthcare personnel, first responders, and other frontline workers under real-world conditions and concluded that the mRNA vaccines (Pfizer-BioNTech and Moderna) were 90% effective at least two weeks after the second dose.

The lifespan of these vaccines isn’t clear yet, but research suggests that the Moderna vaccine offers strong antibody protection for at least six months following the second dose.

The leaders of the Phase 3 trial say they will keep collecting blood samples from the study group to check for immunity throughout the first year after vaccination. In the past, viruses in the same virus families don’t generate long-lived immune responses, the trial report notes. 

Lab studies of the Moderna vaccine also suggest protection against variants, including B.1.1.7 first found in the United Kingdom, yet there may be a significant drop in protection for B.1.351 first found in South Africa. On March 10, 2021, Moderna announced the launch of a booster study targeting the B.1.351 variant. In March the company also began a Phase 1 trial to test a potentially refrigerator-stable mRNA vaccine candidate for COVID-19.

Limited studies also suggest the vaccine provides protection against the Delta (B.1.617.2) variant. One new study (which has not yet been peer-reviewed) found one dose of the Moderna vaccine to be 72% effective.

How Many Doses Are Available?

Moderna received emergency use authorization from the FDA for its vaccine on December 18.

According to the CDC, all doses of the vaccines that have been purchased by the U.S. government are available to citizens free of charge.

In addition to the 300 million doses already ordered by the U.S. government, it has the option to purchase 200 million more.

As of May 2, 2021, Moderna had supplied 131.8 million doses to the U.S. and 106.7 million of these doses had been administered, according to the CDC. Moderna also announced that it is on track to deliver 200 million doses by the end of June.

The company has also reached agreements to supply the vaccine to several other countries, including:

  • European Union: 310 million doses with an option for another 150 million doses
  • Japan: 50 million doses
  • Canada: 44 million doses
  • South Korea: 40 million
  • Philippines: 20 million doses
  • Colombia: 10 million doses
  • Israel: 6 million doses
  • Switzerland: 13.5 million doses
  • United Kingdom: 17 million doses
  • Taiwan: 5 million doses

While the vaccine itself is free to the public, vaccine providers who administer the vaccine may seek reimbursement for administrative costs from public and private insurance plans, as well as through the Health Resources and Services Administration’s COVID-19 Uninsured Program for people with no public or private health insurance. No one receiving a vaccine can be charged any fees.

Who Can Get the Moderna Vaccine?

Everyone 18 and older is now eligible for the Moderna vaccine, according to the CDC.

State and local health departments are coordinating efforts to distribute doses of the vaccines as they become available. The vaccine is typically available in healthcare centers and retail locations like pharmacies that administer other vaccines. Many states also have mass vaccination sites.

The Moderna vaccine is given in two doses that are 28 days apart. The CDC recommends that the second dose be given as close as possible to the 28 days, yet grants a four-day grace period when it can be given slightly earlier and allows the second dose to be given within 42 days of the first dose in cases where the 28-day window isn’t feasible.

In August 2021, the FDA authorized a third dose of the vaccine for some people who are immunocompromised.

When Will Children Be Able to Get the Vaccine?

Children are not yet eligible receive the vaccine, as trials have only been conducted in adults. Moderna began recruiting participants for a clinical trial in 12- to 17-year-olds in December and has fully enrolled 3,000 participants.

In March 2021, Moderna announced the start of a trial for younger children ages 6 months to 11 years old. It will enroll approximately 6,750 healthy participants and will have two parts: The first part will evaluate two different vaccine dosage options in children ages 2 to 11 and three dosage options in children ages 6 months to under 2 years old. After dosages are evaluated and selected, the second part of the trial will compare the vaccine to a placebo.

Children and teens may be able to receive the vaccine later in 2021.

Side Effects and Adverse Events

People who took part in the study were asked to record any reactions to the vaccine, either to the area where the vaccine was injected or that they experienced overall. Pain at the site where the vaccine was injected and overall tiredness were the most common side effects in the Phase 3 trial.

Systemic effects are reactions that affect the entire body, and headache and fatigue topped that list and were most common in the vaccine group. Less than 20% of the people who were vaccinated report a fever after the second dose.

Local effects, on the other hand, affect only a small, limited area. The most common effect in this category was pain at the injection site.

The severity of reactions increased with the second dose of the vaccine. Few reactions were rated as severe with the first dose of the vaccine, but several were rated as severe after the second dose. The most common reactions reported by participants after the second dose of the vaccine were:

  • Pain at the injection site
  • Fatigue
  • Headache
  • Muscle aches
  • Chills
  • Joint pain

Nausea or vomiting, fever, red or swollen areas at the injection site, and swollen or enlarged lymph nodes were also reported. 

The percentage of serious adverse reactions was the same for the placebo and vaccine groups (0.6%) and did not indicate any safety concerns. There was also no evidence of vaccine-associated enhanced respiratory disease in the trials. Previous vaccines for coronavirus in veterinary use and animal models have led to respiratory problems related to vaccination.

More observation will be done on the study groups as time goes on, and more studies are planned on special populations, like children.

Although it’s rare, serious allergic reactions can occur after receiving the Moderna vaccine. The Vaccine Adverse Event Reporting System (VAERS) reported that there were 10 cases of anaphylaxis, a life-threatening allergic reaction, after about 4.04 million first doses of the Moderna vaccine (2.5 cases per million doses). Most cases occurred within 15 minutes of vaccination and no deaths were reported.

Risk of Myocarditis and Pericarditis

On June 25, 2021, the FDA announced an update to the Moderna and Pfizer COVID-19 vaccine fact sheets for healthcare providers and vaccine recipients and caregivers about the rare risk of developing myocarditis (inflammation of the heart muscle) and pericarditis (inflammation of the lining outside the heart).

The CDC reported a rate of 12.6 cases per million second doses of Moderna’s or Pfizer’s vaccine within three weeks following vaccination among 12- to 39-year-olds. Cases have been predominately reported in male adolescents and young adults age 16 and older, with symptoms typically occurring within a few days after receiving the vaccine. Most people who developed these conditions have responded well to medication and rest.

The CDC continues to recommend the COVID-19 vaccine for those 12 years and older given the suggested increased risks of these conditions. (Pfizer’s vaccine is currently the only COVID-19 vaccine approved for ages 12 and over.)

Warning Symptoms

Seek immediate medical attention if you experience any of the following symptoms after vaccination:

  • Chest pain
  • Shortness of breath
  • Feelings of having a fast-beating, fluttering, or pounding heart

Funding and Development

Moderna worked with the National Institutes of Health and the U.S. Department of Health and Human Services to develop its vaccine. The company received about $1.6 billion in federal funding through the Biomedical Advanced Research and Development Authority (BARDA)—a U.S. government program working to speed up the manufacture and distribution of vaccines to fight COVID-19. Each time the U.S. government exercised its option for an additional 100 million doses from Moderna it cost around $1.65 billion, bringing the total cost to about $5.75 billion.


Related Articles
Choosing foods to diet after a heart attack

All cardiovascular specialists agree that a healthy diet is important to reduce the risk of coronary artery disease (CHD) Read more

Different types of hysterectomies.

A hysterectomy is the surgical removal of all or part of a woman's uterus . Hysterectomy is usually done Read more

Esthetician: experience, specialties and training

An esthetician is a person who specializes in cosmetic skin care. Cosmetologists (sometimes called estheticians ) are not medical Read more

Benefits, Side Effects, Dosages, and Interactions.

CBD oil is an extract from Cannabis indica or Cannabis sativa , the same plants that produce marijuana when Read more