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A new variant of SARS-CoV-2 is spreading rapidly in the United Kingdom, with over 1,400 cases since September. SARS-CoV-2, the virus that causes COVID-19, generally accumulates mutations slowly over time, but this new variant had rapidly accumulated many mutations.
If this new version of the virus is here to stay, as it seems to be, what does that mean? Will this new version of the virus replace the old one? Will it be easier to catch? And, most importantly, will current vaccines continue to be effective?
This interests me because I am an evolutionary microbiologist who studies the link between the transmission and the evolution of infectious diseases. In particular, I spend a lot of time considering the effects of vaccines on the evolution of pathogens and the effects of the evolution of pathogens on the impact of vaccines.
What is the new SARS-CoV-2 mutant that has appeared?
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The new version of SARS-CoV-2 – called line B.1.1.7 – is spreading in the UK and possibly beyond. The differences between the old and the new virus include 23 mutations in the genetic code of the virus that altered four viral proteins.
Eight of these 23 mutations affect the protein spike. This is important because the spike protein allows the virus to enter human cells and is a key target of our immune response, both in fighting the virus during infection and in protecting us against the disease after vaccination with Pfizer and Moderna vaccines.
If the changes in the spike protein help the virus to enter human cells more easily, then the virus could be transmitted more easily from person to person.
These mutations can also alter how well the host’s immune system fights the virus, potentially reducing the effectiveness of current vaccines.
What is different about this new version of SARS-CoV-2?
Samples of the new virus isolated from patients suggest that this variant has increased in relative frequency over the last three months.
The increase in frequency is worrying, as suggested – but not demonstrated – that isolates B.1.1.7 of SARS-CoV-2 are more transmissible than the original virus. Some have estimated that the new virus can be up to 70% more transmissible than the old virus. Although these estimates are consistent with the data, it is far too early to draw a definitive conclusion.
If this increase in transmissibility is confirmed, it could be due to mutations in the protein that allows it to bind more closely to the ACE2 receptor, which provides a gateway for the virus into human cells.
But it could be due to any of the other changes in the virus.
Is it more dangerous? If so, why?
If the new version, B.1.1.7, is indeed more transmissible than the old virus, it will be more dangerous in the sense that it will make more people sick.
However, I am not aware of any good evidence that there is any difference in the severity of the disease caused by the new version of this virus compared to the older one. That being said, with so few known cases, it may still be too early to tell.
Will Pfizer and Moderna vaccines continue to be effective against this new strain?
Both Pfizer and Moderna vaccines work by training our immune systems to recognize a specific version of the spike viral protein. The version of the spike protein used by the vaccines was designed to match that of the old virus, not that of the B.1.1.7 virus. This means that vaccines may become less effective than expected if this new virus spreads widely.
The mismatch of the vaccine virus is an ongoing challenge for scientists tasked with developing the seasonal flu vaccine. But even with a mismatch of the vaccine virus, the flu vaccine reduces the likelihood and severity of the disease.
Therefore, the question is not whether the vaccines will be effective, but how effective they will be. The severity of the mismatch matters, but the only way to determine its impact in this case is through scientific study and, as far as I know, no data has been collected on this yet. In other words, it is too early to say whether and how this new variant will affect the overall effectiveness of Pfizer and Moderna vaccines.
Should people still receive the new mRNA vaccine?
The emergence of this new B.1.1.7 makes it even more important for people to be vaccinated as soon as possible.
If this new version is more communicable or if the vaccine is less effective due to a mismatch of the vaccine virus, more people will need to be vaccinated to gain immunity from the herd and to control this disease.
Moreover, we now have evidence that the spike protein of SARS-CoV-2 can change drastically in a short time, and therefore it is essential to get the virus under control in order to prevent its further evolution and completely undermine vaccination.
David Kennedy, assistant professor of biology, Penn State
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