During every coronavirus infection, the SARS-CoV-2 virus makes many new copies of itself.


For each new copy, the virus has to duplicate its genome. And during this duplication, small errors can occur, so that each new copy of the genome is slightly different from the last.

In short, these errors are the mutations that create a coronavirus variant. These mutations happen all the time, creating more and more variants, but most have no effect on how the virus behaves.

Occasionally though, a mutation will cause a change in some aspect of how the virus behaves. These are the “variants of concern” that we have been hearing about.

Why are so many coronavirus variants emerging now?

Because of the constant mutations that occur as the virus replicates, there are likely thousands or even millions of variants of SARS-CoV-2.

The more times the virus replicates (and the greater number of people infected), the more mutations that will occur and the more variants we will have. With over 112 million cases of COVID-19 worldwide, it is normal and expected for there to be this many variants.

However, headlines seem to be filled with news of new variants of concern. The reason for this is not that we’re suddenly getting more virus mutations or variants, but that the virus likely now has more selective pressure for variants that help it in some way.

What does this mean? Well, earlier in the pandemic, the majority of the world did not have any protective immunity against the virus. But now more and more people have either been infected or vaccinated, giving protection from further infection. Because of this, any virus with a mutation that doesn’t produce an immune response, will likely spread better (as we are seeing in the South African B.351 variant).

Read more about coronavirus variants:

Should we be worried about any new variants?

As long as the virus continues to spread, we will have new variants. Most of these variants will not affect the pandemic at all. However, there are two areas of concern.

First, it is possible that a new variant will emerge (by chance) with an altered behaviour that happens to make the virus more transmissible or deadlier. This is not an inevitability. It is just as likely that the virus would mutate to cause more mild disease.

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The second and larger concern is that the virus will mutate and evade an immune response. This means the virus could either re-infect people or infect people that have been vaccinated. We are currently seeing this change with the South African B.351 variant and the Brazilian P.1 variant.

Immune-evading mutations are beneficial for the virus as they allow the virus to infect more people. Thus, as more and more people build protective immune responses (either after recovering from infection or by vaccination), the pressure on the virus increases and the likelihood of immune-evading variants increases.

For comparison, the influenza virus changes enough every year that we need a new vaccine. SARS-CoV-2 doesn’t mutate as rapidly as the flu, but there is a concern that the continual emergence of new variants will necessitate new booster vaccines at some regular interval.

Are we doing anything to encourage more variants?

Unfortunately, the actions of many countries are encouraging more variants.

But this is not because we are causing the virus to mutate faster. By not effectively stopping the spread of the virus, we are giving the virus more chances to mutate. And the more COVID-19 infections, the greater the chances of a new variant emerging with changed behaviour.

It is possible that this generation of new variants could be enhanced by delaying the time between the first and second coronavirus vaccine dose in the UK.

The rationale for delaying the second vaccine dose is to enable as many people as possible to get some level of vaccine-induced protection as quickly as possible. This seems like a good strategy for a limited supply of vaccine.

However, we know that after one vaccine dose it’s still possible to be infected by the virus. And there is a chance that these infections could drive the evolution of the virus toward variants that evade the immune system.

There is no evidence that this is currently happening. But just as a partial course of antibiotics could lead to antibiotic-resistant bacteria, it is possible that a partial course of vaccine jabs could lead to immune-evading SARS-CoV-2.

Can we do anything to stop more variants emerging?

The single best thing we can do to stop new variants emerging is to reduce the number of coronavirus infections worldwide. This is because each new infection has a chance of creating a new variant that behaves differently.

We all want to rely on vaccines as a quick way out of the pandemic. But, on their own, vaccines will likely result in new variants that evade immunity – which is possible in a matter of months.


As scientists argue, we need to continue to support our vaccines with strong public health measures.

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Jeremy Rossman is a Senior Lecturer in Virology and President of Research-Aid Networks, University of Kent. His research focuses on the process of infectious disease outbreaks, and he has contributed to studies published in journals including PLoS Pathogens, Bioinformatics and Cell.