Which COVID vaccine is the best?

Doctor filling syringe with COVID-19 vaccine
Photo via Marco Verch Professional Photographer/Flickr (CC BY 2.0)
  • This story is regularly updated for relevance. Last updated: July 15, 2021

As COVID-19 inoculations ramp up across the United States, an important question has arisen: Which COVID vaccine is the best?

The three vaccine options currently available come from Pfizer, Moderna, and Johnson & Johnson. AstraZeneca could soon be a fourth option, but as of early June, it still hadn’t asked the FDA for emergency approval.

Experts advise that eligible people receive whichever vaccine option is provided. For anyone wondering which vaccine is “best,” however, there are a few key differences between them.

Pfizer and Moderna

The main thing that differentiates the Pfizer and Moderna vaccines from their peers is their use of messenger RNA, or mRNA. mRNA delivers a small amount of genetic code to cells in order to replicate the surface protein “spike” of the virus. These surface proteins then activate the immune system, which in turn teaches itself to identify the spike as a foreign entity. This allows it to develop antibodies and other immunity weapons to fight off recurrences of the virus.

The vaccines also have similar effectiveness and suggested dosing intervals. The Pfizer-BioNTech vaccine, which has 95% efficacy, has a recommended interval of 21 days between the first and second doses. The Moderna vaccine has 94.1% efficacy, with 28 days suggested between the first and second dose.

Currently, the Pfizer-BioNTech is approved for people aged 12 and over, while Moderna can be administered to adults aged 18 and older. On June 10, Moderna asked the FDA to grant it emergency approval to give the vaccine to everybody 12 or older.

Johnson & Johnson

Johnson & Johnson’s option, known as a “viral vectored vaccine,” works in a somewhat different way to produce a similar outcome. It administers a harmless “adenovirus”—which comes from the same family of viruses that cause common colds—to carry genetic code for the SARS-CoV-2 spike protein. Upon entering cells, the adenovirus uses that code to produce spike proteins to trigger the immune system. 

The Johnson & Johnson vaccine is comparatively unique. It requires only one dose to achieve 66% protection against moderate to severe infection within 14 days after vaccination. It jumps to 85% efficacy against severe disease once 28 days have passed since vaccination. A large clinical trial reported no instances of hospitalization or death among people who received the vaccine. 

This vaccine is currently approved for people age 18 and older, though it certainly ranks well below Pfizer and Moderna when it comes to popularity in the U.S.


The Oxford-AstraZeneca COVID-19 vaccine, like Johnson & Johnson’s option, uses a viral vector adenovirus. The AstraZeneca vaccine uses ChAdOx1—a modified version of a common cold found among chimpanzees—to deliver the code that prompts production of the spike protein. Unlike the Johnson & Johnson vaccine, however, the Oxford-AstraZeneca vaccine requires two doses, administered four weeks apart.

Researchers at Oxford University reported on March 22 that the AstraZeneca COVID-19 vaccine was 79% effective at preventing symptomatic infection. After the pharmaceutical company was accused of “cherry-picking” clinical trial data by the New York Times, however, an independent panel found that a 69-74% efficacy rate was more accurate.

The cherry-picked data shouldn’t scare anyone away from the Oxford-AstraZenec vaccine. The New York Times characterized the dispute as being “about the degree of effectiveness of a vaccine that is indisputably effective” in hopes the discrepancy wouldn’t compromise public trust.

If given a choice, which should you go with?

There is no definitive way to determine which COVID vaccine is “best.” Regardless of which option you’re able to receive, all four vaccines are 100% effective at preventing severe cases of COVID-19. Leading experts say it’s imperative to get everyone vaccinated, regardless of which company supplies the dose. 

Particularly since the delta variant has become the most dominant strain in the U.S.

Dr. Sandra Fryhofer, an Atlanta-based general internist who serves as a liaison to the Centers for Disease Control and Prevention’s Advisory Committee on Immunization Practices (ACIP) for the American Medical Association, said in a recent interview that all three COVID-19 vaccines available “are safe and effective.”

“ACIP has expressed no preference for any of these three authorized vaccines,” she told the AMA’s website. She’s advising people to “get vaccinated as soon as you can, when it’s your turn, and with whichever vaccine is available. That’s how we’re going to end this pandemic.”

Read more on the coronavirus vaccine:

Sources: AMA, STAT News, Mayo Clinic

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