An Overview of the Moderna COVID-19 Vaccine

Moderna's vaccine is the second to receive U.S. approval

As cases of novel coronavirus (COVID-19) rise in a predicted winter surge, a number of vaccines are in the pipeline to help bring an end to the pandemic. One of these is Moderna’s vaccine, called mRNA-1273. Moderna’s vaccine is the second vaccine to receive emergency use authorization from the U.S. Food and Drug Administration (FDA).

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Moderna, an American biotechnology company based in Cambridge, Mass., 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 by 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 September, results of the phase I clinical trial were published.

When Was Moderna's Vaccine Officially Approved?

American health officials granted Moderna’s vaccine an emergency use authorization on Dec. 17, 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 (ribonucleic acid) vaccine is 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 spiked protein that makes COVID-19 so potent
  • Teaching immune cells to recognize and fight similar spiked 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. 

How Was Moderna's Vaccine Tested?

Moderna’s vaccine was tested in adults aged 18 to 55. The first phase of the trial investigated three different doses—25-, 100-, and 250-micrograms—given twice, 28 days apart. By phase 3 of the trial, Moderna zeroed in on a two-dose formula of 100-micrograms each, given in two doses about four weeks apart. People involved in the study were not screened for COVID-19 before starting the trial.

How Effective Is It?

Researchers that conducted the trial 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 (pseudotype 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, 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 immune responses in those who had recovered 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 lifespan of these vaccines isn't clear yet, but the leaders of the 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. 

When Will It Be Available?

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

Like the Pfizer vaccine before it, the Moderna vaccine is expected to roll out quickly, with the first doses expected within a week of the approval.

Distribution may be a bit easier for Moderna than Pfizer since it’s vaccine can be stored at standard refrigerator temperatures for 30 days, or frozen at -20 degrees Celsius for six months. The Pfizer vaccine has to be stored at much colder temperatures.

As far as cost goes, Moderna announced during an internal conference call in August that the vaccine could cost between $32 and $37 per dose, but final prices may change when the worst of the pandemic has passed.

According to the (CDC), however, doses of the vaccines that have been purchased by the U.S. government will be available to citizens free of charge.

Moderna has announced that the U.S. government has already ordered 200 million doses of the vaccine, plus an option for 300 million more. The first 20 million doses could be available as early as late December, according to Moderna.

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

  • European Union: 80 million initial doses with an option for another 80 million doses
  • Japan: 50 million doses
  • Canada: 40 million doses with an option for an additional 16 million
  • Switzerland: 7.5 million doses
  • United Kingdom: 7 million doses
  • Israel: 6 million doses

A number of other countries have also placed orders with the company, according to Moderna, but the number of doses ordered was not disclosed.

While the vaccine itself will be free if purchased by the government, there could be fees charged by vaccine providers who administer the vaccine. Reimbursement programs for these administrative costs should be available through both public and private insurance plans, as well as through the Health Resources and Services Administration's Provider Relief Fund for people with no public or private health insurance.

Who Can Get the Moderna Vaccine?

Now that vaccines are on the way, the question becomes who will get them and when? The CDC anticipated limited supplies in the initial phase of the vaccination program, and recommendations for who should receive the vaccine first were made by CDC's Advisory Committee on Immunization Practices (ACIP) in December 2020 based on earlier guidance from the National Academies of Sciences, Engineering, and Medicine.

In terms of the order, federal health officials have decided that health care workers and people living in long-term care facilities should be the first to receive the first of the vaccines, which will be limited at first as manufacturing ramps up.

According to the CDC, there are more than 21 million health care providers in the U.S., and about 3 million Americans living in long-term care facilities. Each of these people would need to receive two doses of the top vaccine contenders so far, totaling nearly 50 million doses needed for the initial phase of vaccination. The CDC estimates it will take several months before the supply of vaccines catches up to the demand.

Guidance on who will receive the vaccine and when will be decided as supplies become available. The U.S. alone has a population of about 330 million—meaning nearly 700 million vaccine doses will be needed to vaccinate all of America as other vaccines follow a two-vaccine dose.

Although little information is available yet on the specifics of when everyone will receive the vaccination, and where they can get it, state and local health departments will be coordinating efforts to distribute doses of the vaccines as they become available. The vaccine should be available both in physician offices and retail locations like pharmacies that administer other vaccines.

When Will Children Be Able to Get the Vaccine?

Children will not receive the vaccine at first, as trials have only been conducted in adults. Trials in younger groups are still in the planning stages as of late 2020. 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. They were also asked not to regularly take any acetaminophen, fever reducers, or pain relievers during the trial period so that vaccine reactions would be accurately revealed. Pain at the sight where the vaccine was injected and overall tiredness were the most common aide effects, and no serious reactions or adverse reactions were reported.

Systemic effects are reactions that affect the entire body, and headache and fatigue topped that list and were most common in both the first vaccine and second vaccine groups. 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. Some joint pain and hardened red areas at the injection site were reported in the 100- and 250-microgram groups, but not in the 25-microgram vaccine group. Otherwise, the prevalence of reactions was relative to the dose, with more reactions reported in the higher-dose vaccine groups.

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:

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

Nausea, fever, and hardened red areas at the injection site were reported in the 100- and 250-microgram groups only, not in the 25-microgram group. Like the first dose of the vaccine, reactions were reported more often in people who received higher doses of the vaccine.

Despite the fact that there were no severe adverse effects in the vaccine trial, even the authors of the report suggest more advanced 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 original study groups as time goes on, and more studies are planned on special populations, like children. Moderna announced plans to study the vaccine in minor populations in mid-December, but no specifics about the study have been announced yet.

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 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. Moderna could receive another $1.5 billion if the U.S. exercises its option to purchase additional doses of the vaccine.


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