What is a COVID-19 variant strain?

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.