How Does Moderna's Vaccine Measure Up To Pfizer's?

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.

This news followed a December 11 emergency use authorization for the COVID-19 vaccine developed by Pfizer and BioNTech. This vaccine is authorized for people ages 16 and older.

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.

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. 

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 at Envision 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). Moderna will be shipped at 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.

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.

The Moderna vaccine is given in two doses that are separated by one month (28 days). The Pfizer-BioNTech vaccine is given in two doses that are three weeks (21 days) apart.

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? 

Moderna said in a November 16 news release that it expected to ship approximately 20 million doses in the U.S. by the end of 2020, and it remains on track to manufacture 500 million to 1 billion doses globally in 2021.

Pfizer and BioNTech announced in a November 9 news release that it expected a global production of up to 50 million doses in 2020 and up to 1.3 billion doses by the end of 2021.

Both companies are distributing the vaccines following a playbook for 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 the Journal 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.”

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 our coronavirus news page.