COVID-19 Vaccines Are Effective Against Key Variants of Concern

Doctor with vaccine syringe and gloves.

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Key Takeaways

  • Two new studies show that the Pfizer vaccine is highly effective at protecting against some key variants of concern.
  • Experts remain hopeful that the mRNA vaccines will help slow the spread of viral variants around the world.
  • Moderna announced results from a test for a booster shot, including one aimed at neutralizing the B.1.351 variant.

The Pfizer-BioNTech vaccine can protect against two key viral variants, according to new real-world data from Qatar. It is the strongest evidence yet that the vaccine can stop two of the strains most concerning to scientists.

In a letter published last week in the New England Journal of Medicine, researchers report that the Pfizer-BioNTech vaccine was about 90% effective at preventing infections caused by the B.1.1.7 variant. The variant, which now accounts for two-thirds of the cases in the U.S., is highly infectious.

Perhaps more significant is that against the B.1.351 variant, which scientists have worried is capable of evading most immune response, the vaccines protect against 75% of all infection. Plus, protection against severe death and disease remained remarkably high at more than 97%.

“This is really good efficacy,” study author Laith Abu-Raddad, PhD, professor of population health sciences at Weill Cornell Medical College, tells Verywell. “It's not perfect … but 75%, against what is probably the nastiest of all variants of concern—that is very, very good news.”

Another study published in The Lancet on the same day used national surveillance data from Israel to track COVID-19 related hospitalizations, severe disease, and death amongst people more than 16 years old. In Israel, where nearly all the infections were attributable to the B.1.117 variant, the Pfizer vaccine proved 95% effective at preventing COVID-19 infections.

“I don't think we could hope for better news than this," Paul Goepfert,MD, director of the Alabama Vaccine Research Clinic, who was not involved with the studies, tells Verywell. "It's pretty amazing how well the vaccines are holding up against these variants."

The Vaccines Are Effective Against Variants

These two studies focused on the vaccine by Pfizer. Other recent studies indicate that the vaccines by Moderna, NovaVax and Johsnon & Johnson were similarly effective against the variants originally discovered in the U.K., South Africa, and Brazil.

The vaccine by Johnson & Johnson proved to be 64% effective in preventing mild to severe COVID-19 against the B.1.351 variant and 68% effective when a little over two-thirds of COVID-19 cases were attributable to the P.2 variant. In a study where 90% of the cases were attributable to the B.1.351 variant, the NovaVax vaccine was 60% effective.

The AstraZeneca vaccine proved largely ineffective at preventing any kind of disease when tested in South Africa. In a small double-blind randomized study published in the New England Journal of Medicine, researchers showed that the vaccine was only about 20% effective at preventing disease from the B.1.351 variant.

The B.1.351 variant is particularly difficult to neutralize because it carries two mutations which make it easier for the virus to infect healthy cells. To minimize COVID-19-related illness and death, scientists have been looking for ways to limit the spread of this variant.

“This is basically a cat-and-mouse game with the virus," Abu-Raddad says. "We try to make a vaccine that generates neutralizing antibodies against specific variants, but then it evolves."

What This Means for You

Experts say the best way to quell the spread of viral variants in the U.S. and throughout the world is to increase the number of people who are vaccinated. When more people are vaccinated, there are fewer chances for the virus to infect people and mutate into new variants. If you haven't been vaccinated, find an appointment near you at

How Are the Booster Shots Faring?

Earlier this month, Moderna announced the results from tests exploring two booster shot options. One is a third shot of the original vaccine formula currently used for their two-dose vaccine. The other is a third shot specifically tailored to the B.1.351 variant.

In the small study of 40 participants, antibody levels against the original strain of the virus remained high six to eight months after vaccination. However, in half of the participants, antibodies against the B.1.351 and the P.1 variant—originally detected in Brazil—had declined. It appeared that the formula designed to combat the B.1.351 variant was more effective in doing so. The company says it is also testing a combination formula that mixes the original vaccine with the dose tailored for the variant.

“We are actually in a better situation than we may think because what we have already is working quite well again the variants,” Aub-Raddad says. “We may have boosters, but then maybe that's it. It's time, hopefully soon, to go back to our normal life.”

New Variants of Concern Emerge

In India, COVID-19 cases are surging, reaching the highest daily tally of new infections ever recorded globally. A new variant, called B.1.617, emerged during the spike. The WHO named it a “variant of concern” because it appears to be highly transmissible.

Scientists have yet to collect comprehensive real-life studies data about how the existing vaccines work against this and the P.1 variants. But some early tests indicate various vaccines may hold up against the double-mutant strain.

Goepfert says that laboratory tests have generally held up against findings from real-world trials for other variants, and he expects these to match well too. Abu-Raddad agrees, saying he is optimistic that the vaccines will demonstrate good effectiveness against these variants.

“It's really hopeful that right now we don't have a variant that seems to get around the vaccine-induced responses,” Goepfert says.

Controlling Future Variants

Abu-Raddad says that while this data is helpful for understanding how fully vaccinated people perform, scientists have yet to investigate how well the two-shot vaccines perform after just one dose. This will be especially important for people living in places where officials have opted to delay the second dose for many people in favor of doling out first doses to more people.

In the meantime, experts say it’s crucial to get as many people vaccinated as possible in the U.S. and abroad. Not only does vaccination protect the individual, but it also drives down the chances of variants getting out of control. With higher vaccination rates comes fewer opportunities for the virus to infect people and mutate into new variants.

“You can sort of think of it as a fire—if you just have a few sparks going around it's easy to stamp those out," Goepfert says. "But when the fire starts raging, it's extremely difficult to get it under control, even with your best weaponry. I suspect that one day we are going to get a variant that's resistant to vaccine, so I hope we can get ahead of it before that.”

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.

5 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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  2. Centers for Disease Control and Prevention. COVID Data Tracker.

  3. Haas E, Angulo F, McLaughlin J et al. Impact and effectiveness of mRNA BNT162b2 vaccine against SARS-CoV-2 infections and COVID-19 cases, hospitalisations, and deaths following a nationwide vaccination campaign in Israel: an observational study using national surveillance data. The Lancet. 2021;397(10287):1819-1829. doi:10.1016/s0140-6736(21)00947-8

  4. Sadoff J, Gray G, Vandebosch A et al. Safety and Efficacy of Single-Dose Ad26.COV2.S Vaccine against Covid-19. New England Journal of Medicine. 2021;384:2187-2201. doi:10.1056/nejmoa2101544

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By Claire Bugos
Claire Bugos is a health and science reporter and writer and a 2020 National Association of Science Writers travel fellow.