What's the Difference Between the 3 Available COVID-19 Vaccines?

Although there are now three COVID-19 vaccines available, in general, people don’t get to choose which one they receive. Supplies are still limited—vaccination locations usually getting only one type at a time.

The major difference among the three vaccines is that both the Pfizer-BioNTech and Moderna vaccines require two shots a few weeks apart and the Johnson & Johnson vaccine only requires one shot.

But aside from the convenience of “one and done” for Johnson & Johnson, are there any real differences between the three vaccines? Should anyone try to receive their immunization with one vaccine rather than another? The answer from experts is a unanimous no.

Each Vaccine Is Highly Effective

The three vaccines do have some differences in how effective they are at preventing COVID-19 illness. Keep in mind that while efficacy rates matter, they can be misunderstood or be overemphasized. Efficacy describes the rate of effectiveness against developing any symptoms, which is important, but not as important as vaccine's ability to prevent severe COVID-19 cases, hospitalization, and death.

Pfizer-BioNtech

Phase 3 clinical trial data from November shows Pfizer's vaccine is 95% effective at preventing COVID-19.

Moderna

Moderna's Phase 3 clinical trial data shows the vaccine is 94.5% effective at preventing COVID-19. It appears to be a bit less effective (about 86%) in people age 65 and older.

Johnson & Johnson

The Johnson & Johnson vaccine is reported to be 86% effective at preventing severe COVID-19 and 72% effective at preventing severe disease.

Still, comparing the efficacy rates for the vaccines is like comparing apples to oranges, immunologist Robert Quigley, MD, DPhil, SVP and Global Medical Director of International SOS, tells Verywell. The Johnson & Johnson vaccine received its emergency use authorization from the Food and Drug Administration (FDA) nearly three months later than later than Pfizer and Moderna, when more variants of the virus may have been circulating, Quigley explains.

Amber D’Souza, PhD, professor of epidemiology at Bloomberg Johns Hopkins School of Public Health, agrees.

“A lot of the research that was done on the vaccines was done before the variants emerged, but they are still providing robust protection against these variants so far,” she tells Verywell.

Side Effects Are Not Uncommon, but Usually Mild

Most side effects of the vaccines are mild and usually occur within a day or two of the injection. These are signs that the vaccine has charged up the body's immune system to recognize the virus.

Pfizer-BioNTech

According to the FDA, side effects of the Pfizer-BioNTech vaccine are more common after getting the second dose of the vaccine. Common side effects may last a few days, and can include:

• pain at the injection site
• tiredness
• headache
• muscle pain
• chills
• joint pain
• fever

Phase 3 clinical trial data shows the most commonly reported side effects that were rated as severe among the 43,000 participants were fatigue (3.8% after the first or second dose) and headache (2% after the second dose).

Moderna

The FDA also says side effects of the Moderna vaccine are more common after the second dose, but don't last long. Phase 3 clinical trial data shows that among the 30,000 participants, the most commonly reported second dose side effects were:

• fatigue
• muscle ache
• joint stiffness
• headache
• pain
• erythema/redness at the injection site

At 9.7%, fatigue was the symptom most commonly rated as severe.

Johnson & Johnson

So far, the side effects of the Johnson & Johnson vaccine seem less severe than the Pfizer and Moderna vaccines. Only about 49% of people report arm pain, and about 55% report symptoms like fever, headache, and fatigue, compared to 80% of people receiving both doses of the Pfizer and Moderna shots.

According to the FDA analysis of initial safety information for Johnson & Johnson's vaccine, the most common reactions after the one-dose shot include:

• Injection site pain, redness, or swelling
• Fatigue
• Headache
• Muscle aches
• Nausea
• Fever

They're Made Differently

The Pfizer-BioNtech and Moderna vaccines are manufactured using messenger RNA (mRNA) technology, and are the first mRNA vaccines to be used in humans.

The goal of any vaccine is to prepare the immune system to fight a virus. Unlike older types of vaccines, mRNA vaccines do not use either live or deactivated virus to do this. Instead, mRNA vaccines use a small piece of messenger RNA to insert the instructions for the viral protein that triggers the immune response. This mRNA technology allowed researchers to rapidly create a vaccine against COVID-19 once the genes of the virus were identified.

A viral vector vaccine like Johnson & Johnson, on the other hand, uses a virus similar to the SARS-CoV-2 virus, called a vector, but one that has been modified so that it cannot replicate in the body. This vector then causes the immune system to be charged up to fight COVID-19 if you ever become infected. Viral vectors are the way that most vaccines, like polio and measles vaccines, have been made for decades, but they take longer to make than do the new mRNA vaccines.

According to Quigley, the manufacturing technology is different, but “the end game is the same: to activate the immune system to protect us against the next exposure.”

They're Stored Differently

There are differences in storage needs among the different vaccines: the Pfizer-BioNTech vaccine originally required storage in ultracold freezers (-112 to -76 degrees F) before it could be defrosted and used. This caused logistical problems for distribution, because not every transportation system or vaccination location had access to ultracold freezers. However, the Food and Drug Administration (FDA) changed this requirement when Pfizer was able to show that regular freezers could be used to store the vaccine for up to two weeks.

Both the Moderna and Johnson & Johnson vaccines can be stored in refrigerators at between 36 and 46 degrees for up to 30 days. These storage requirements may not matter to the person getting the shot, since those are factors dealt with before the vaccines are administered.  

CDC: Take What You Can Get

According to the Centers for Disease Control and Prevention (CDC), “The CDC doesn’t have a preference for one COVID-19 vaccine over the other and recommends getting the first vaccine available to you,” Kristen Nordlund, a CDC spokesperson, tells Verywell.

“Right now, it is quite clear that all three offer tremendous benefit, and people should take whichever one is made available to them,” D’Souza says. “They should feel confident that all three are safe and effective.” She adds that personally, she would take any of the three.

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.