Do COVID-19 vaccines protect against the variants?

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Do COVID-19 vaccines protect against the variants?
Find out about COVID-19 variant strains.

Matthew Binnicker, Ph.D., Director of the Clinical Virology Laboratory: Variant basically means a mutation that occurs in the virus over time. So just with natural evolution over time, as the virus infects people, it has the opportunity to replicate its genome, and every time it replicates its genome, there are chances for errors or mutations to occur.

We've now been a year with this virus and as it's infected millions of people, it's replicated its genome billions of times and errors have been incorporated. These have resulted in mutations or variants. We fully expected that variants/mutations would occur with this virus.

There are three primary variants or mutations of SARS-CoV-2. One was first identified in the United Kingdom, a second was identified in South Africa, and a third out of Brazil.

The United Kingdom variant has higher potential for transmission, so it's going to spread faster and easier between people. We don't think that it has worse disease outcomes yet, so it doesn't cause more severe disease or lead to a higher rate of hospitalizations. The South African variant also seems to have higher rates of transmission. Then the Brazil variant is still very new and we're learning more about that.

Media outlets and even scientific reports are referring to these viruses by where they were first characterized, or identified. By the time we learn about them, they're spread through many countries, if not throughout the world. So it's more important to understand that this occurs naturally. We expect this to happen.

I think that it's safe to say that the currently circulating strains/variants of SARS-CoV-2, that the vaccines will offer protection against those strains. It's really important to think about efficacy and effectiveness of the vaccine on a continuum rather than a binary yes and no. Now, where that efficacy falls on the continuum, I think we're still learning that. The UK variant appears that the Pfizer and Moderna vaccines, which are very common, will offer strong protection against that strain. The South African variant, there's some evidence showing that the efficacy may be reduced. Now when we talk about reduced, again, it's not going from 95% efficacy to 0. It might be 95% efficacy to 85% efficacy against preventing severe COVID disease.

Viruses can't mutate if they don't replicate. So all of those steps — vaccination, masking, physical distancing — are going to be really important to help drive down the number of infections, and that will slow the emergence of new variants and mutations.

Key takeaways


While research suggests that COVID-19 vaccines are slightly less effective against the variants, the vaccines still appear to provide protection against severe COVID-19. For example:

  • Early research from the U.K. suggests that, after full vaccination, the Pfizer-BioNTech COVID-19 vaccine is 88% effective at preventing symptomatic COVID-19 virus caused by the delta variant. The vaccine is 96% effective at preventing severe disease with the COVID-19 virus caused by the delta variant. The research also showed that the vaccine is 93% effective at preventing symptomatic COVID-19 virus caused by the alpha variant.
  • Early research from Canada suggests that, after one dose, the Moderna COVID-19 vaccine is 72% effective at preventing symptomatic COVID-19 virus caused by the delta variant. One dose of the vaccine is also 96% effective at preventing severe disease with the COVID-19 virus caused by the delta variant.
  • The Janssen/Johnson & Johnson COVID-19 vaccine is 85% effective at preventing severe disease with the COVID-19 virus caused by the delta variant, according to data released by Johnson & Johnson.

More about COVID-19 variants and vaccines