Key Takeaways

On December 18, the Food and Drug Administration (FDA) issued an emergency use authorization (EUA) for a COVID-19 vaccine from the biotechnology company Moderna. The second COVID-19 vaccine authorized, it can be given to people ages 18 and over.

On November 17, Moderna reported the results of a Phase 3 vaccine trial against coronavirus. It said its vaccine is 94.5% effective.

Eight days earlier, Pfizer and BioNTech had announced that their vaccine was 90% effective. The effectiveness was updated to 95% after more Phase 3 trial data was analyzed. Peer review of the data is still pending for both companies.

“Both the Moderna and Pfizer vaccines have had remarkable efficacy in early results from Phase 3 trials,”Don L. Goldenberg, MD, professor in the Departments of Medicine and Nursing at Oregon Health & Science University and author of “How the COVID-19 Pandemic Is Affecting You and Your Healthcare,” tells Verywell. “The initial results from the Moderna study did include vaccine efficacy in high-risk people, either from age or underlying disease."

He added: “Both vaccines use the same technology and thus far have been free of alarming adverse side effects.”

While the more COVID-19 vaccines developed the merrier, you may be wondering how the vaccine candidates differ from one another.

COVID-19 Vaccines:Stay up to date on which vaccines are available, who can get them, and how safe they are.

Results Are Based On a Diverse Pool of Volunteers

Moderna noted in its news release that the study, known as the COVE study, enrolled more than 30,000 participants across the United States. Sixty-three percent of the participants are White, 20% are Hispanic; 10% are Black; and 4% are Asian Americans, according to Moderna’s demographic information. Twenty-five percent of the volunteers are 65 or older.

On the other hand, the 44,000 participants in the Pfizer study are from six different countries: the United States, Germany, Turkey, South Africa, Brazil, and Argentina. “Approximately 42% of global participants and 30% of U.S. participants have racially and ethnically diverse backgrounds, and 41% of global and 45% of U.S. participants are 56 to 85 years of age,” the company noted in a news release. Half of the participants received the vaccine, while the other half were given a placebo.

Pfizer announced on November 18 that its vaccine presented no serious side effects in trials.

Stewart Coffman, MD, MBA, FACEP“We appear to have two highly effective and safe vaccines to fight this virus; both Pfizer’s and Moderna’s vaccines are set to play a role in getting this virus under control. Vaccines are critical public health measures to protect the health and safety of communities and slow the spread of this virus.”

Stewart Coffman, MD, MBA, FACEP

“We appear to have two highly effective and safe vaccines to fight this virus; both Pfizer’s and Moderna’s vaccines are set to play a role in getting this virus under control. Vaccines are critical public health measures to protect the health and safety of communities and slow the spread of this virus.”

The Vaccines Are Stored Differently

While vaccine storage may be something you’ve never thought about, the temperature at which they are stored is extremely important, says Stewart Coffman, MD, MBA, FACEP, senior vice president atEnvision Healthcare.

“It is critical that a vaccine is stored at the appropriate temperature,” Coffman tells Verywell. “Each of these vaccines will be distributed with detailed guidance on how they are to be administered, because if stored at an inappropriate temperature, it will become deactivated and less effective at preventing the spread of COVID-19.”

For Pfizer, that will require storing the vaccine at about -70 degrees C (-94 degrees F). Modernawill be shippedat about -20 degrees C (-4 degrees F), equal to most home or medical freezer temperatures, and have a shelf life of up to six months at that temperature. Moderna’s shelf life is considered to be one of the vaccine’s benefits; once thawed, it can remain stable at standard refrigerated conditions of 2 degrees to 8 degrees C (36 degrees to 46 degrees F) for up to 30 days within the six-month shelf life.

“The stability at refrigerated conditions allows for storage at most pharmacies, hospitals, or physicians’ offices,” the company noted in a news release.

In addition to its ultra-cold temperature requirements, the minimum order that’s required for the Pfizer-BioNTech vaccine is 975 doses. By comparison, Moderna’s minimum is 100 doses, making it potentially more accessible to regions with smaller populations.

The Dosages are Different

Both COVID-19 vaccines are messenger RNA (mRNA) vaccines that carry instructions for our immune cells to make part of a viral protein that triggers an immune response to COVID-19.

Moderna’s vaccine contains 100 micrograms (mcg) of vaccine, and the Pfizer-BioNTech vaccine contains 30 mcg of vaccine. Despite the differences in the vaccine amounts, they have similar overall effectiveness, according to the companies' preliminary data.

When Will the Vaccines Be Distributed?

Both companies are distributing the vaccines following aplaybookfor priority groups from the Centers for Disease Control and Prevention (CDC). The first round of doses are being administered to healthcare workers and residents and staff of nursing homes and then will move to include essential workers and those considered high risk. Once a large number of doses are made available, the vaccine will be made available to the general public.

Once There’s a Vaccine, Is the Pandemic Over?

Not exactly. In fact, even with vaccines, other “low-tech” interventions, like masks and social distancing, will still be required, Anthony Fauci, MD, said in an October 26, 2020 opinion piece he co-authored for theJournal of the American Medical Association.

“It must be emphasized that these interventions will still be needed after a vaccine is initially available,” the authors wrote. “Even if one or more vaccines have high efficacy and uptake in the population, it will take at least several months for enough people to be vaccinated to confer herd immunity on a population basis.”

Fauci: ‘Low-Tech’ Tools Are Our Best Bet For Preventing COVID-19

The Bottom Line

There seems to be good news ahead, Coffman says.

“We appear to have two highly effective and safe vaccines to fight this virus; both Pfizer’s and Moderna’s vaccines are set to play a role in getting this virus under control,” he says. “Vaccines are critical public health measures to protect the health and safety of communities and slow the spread of this virus.”

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 ourcoronavirus news page.

15 Sources

Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.

Moderna, Inc.European medicines agency begins rolling review of Moderna’s mRNA vaccine candidate against COVID-19 (mRNA-1273)Updated November 17, 2020.

Pfizer.Pfizer and Biontech announce vaccine candidate against COVID-19 achieved success in first interim analysis from phase 3 study. Updated November 9, 2020.

Garde D.Pfizer and BioNTech to submit Covid-19 vaccine data to FDA as full results show 95% efficacy. Stat. Updated November 18, 2020.

Moderna.Cove study. Updated October 21, 2020.

Pfizer.Pfizer and BioNtech conclude phase 3 study of COVID-19 vaccine candidate, meeting all primary efficacy endpoints. Updated November 18, 2020.

Moderna.Moderna announces longer shelf life for its COVID-19 vaccine candidate at refrigerated temperatures. Updated November 16, 2020.

Centers for Disease Control and Prevention.Pfizer-BioNTech COVID-19 vaccine questions. Updated December 15, 2020.

Centers for Disease Control and Prevention.Moderna COVID-19 vaccine questions. Updated December 20, 2020.

Centers for Disease Control and Prevention.Understanding mRNA COVID-19 vaccines. Updated December 16, 2020.

Food and Drug Administration. Factsheet for healthcare providers administering vaccine:Emergency use authorization (EAU) of the Moderna COVID-19 vaccine. Updated December 2020.

Centers for Disease Control and Prevention.Grading of recommendations, assessment, development, and evaluation (GRADE): Pfizer-BioNTech COVID-19 vaccine. Updated December 15, 2020.

Biospace.Moderna’s COVID-19 vaccine candidate meets its primary efficacy endpoint in the first interim analysis of the phase 3 COVE study. Updated November 16, 2020.

Lerner AM, Folkers GK, Fauci AS.Preventing the spread of SARS-COV-2 with masks and other “low-tech” interventions.JAMA. 2020;324(19):1935.

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