Editor’s note: Two new strains of the coronavirus that causes COVID-19, called B.1.1.7 and B.1.351, have been found in the United Kingdom and South Africa and are considered to be more transmissible. In this interview, David Kennedy, a biologist who studies the evolution of infectious diseases at Penn State, explains how these new strains are different, which means “more transmissible”, what it means to the public and whether vaccines will be effective against them. .
What are the two new variants of the SARS CoV-2 virus?
In fact, there are a few different variants that are emerging, which you have probably heard of recently. Two of the most common ones that people are talking about and that they are most concerned about are variants B.1.1.7 and B.1.351. They were first detected in the United Kingdom and South Africa. They appear to have been circulating since October at least, but were only noticed in December. The concern with these variants is that they may have some differences in how transmissible they are and how the immune system sees them.
What does ‘most communicable’ mean when it comes to these variants?
The data suggest that both variants are more transmissible. Most of the data available is for the UK variant in particular. It is not yet clear how much more transmissible it is, but current estimates are that it is somewhere between 30% and 80% more transmissible than the original strains out there.
How did scientists come to these numbers? When case peaks in the UK raised concerns, they sequenced the virus from cases during peaks. They saw that there was this new variant. They observed the frequency of this variant further back in time and saw that it was increasing in frequency with time. So it went from very rare to very common. And based on the rate of increase, they estimate it was about 70% or more transmissible than the original virus.
The second way they determined it was more transmissible is through something called a “secondary attack rate”. What they do is, if they know that someone is infected, they can look and see how many of their contacts have been infected. They can do this for people infected with the original strain of the virus and for people infected with this new variant. What they saw was that people who had this new variant were more likely to infect their contacts, and that increase was around 30% to 40%. This means that this new variant is more likely to be passed on to other individuals.
How does a more transmissible variant translate to risk? How does this affect people’s daily risk levels?
The first thing I must say is that there is no evidence that there is an increase in the severity of the disease as a result of these variants. Therefore, it does not seem that it is now more harmful. But the concern is that more people will be infected and therefore, in total, more people will get sick.
But the reason this is so worrying is that you are hit twice by the increase in transmissibility. First, more people will be infected, so you are more likely to be interacting with someone who is infectious. And secondly, the virus is more infectious, so each infected person is more likely to pass it on to you.
With that said, the basic principles of how we should live our lives and how we should control this are essentially unchanged. The mitigation measures we have in place, things like social distance, wearing a mask, avoiding shared interior spaces, reducing any unnecessary risks, are still the best measures we have to try to control this. At least until we all have access to vaccines.
What does this new variant mean for the vaccine’s effectiveness?
If we look at the smallpox vaccine, we never saw the evolution of resistance to it. It is the same for measles, polio and most vaccines we have. We never need to update them and they just keep working.
But there have been vaccines where we need to update them because resistance has evolved. And therefore, part of the concern with these new variants is that there may be an evolution of resistance to the vaccines that are currently being developed.
The reason people are concerned is that many of the mutations in these new variants are at the site targeted by the vaccines, something called the peak protein. But just because we are seeing changes in the peak protein of these variants does not necessarily mean that it will harm the vaccine.
What the researchers saw is that one of the mutations found in the UK and South Africa variants doesn’t seem to have any effect on how our immune system sees the virus, so that’s good news. But another mutation found in the South African variant appears to affect the way our immune response sees the virus.
We learned that if you take the blood serum from someone who was previously infected with the old version of the virus and try to use that serum to stop the virus that contains this new mutation, you will need a higher concentration of the blood serum to neutralize the virus. This means that there is a difference in the way our immune system views the virus. This does not necessarily mean that the vaccine will be less effective. But it is certainly something that needs further study.
These are two of the mutations. There are many more mutations in these variants, which scientists need to continue to study.
The summary here is that at least one of the mutations appears to be relevant, but there is no good evidence to suggest that this means that the vaccines will not be effective. Vaccines tend to be robust against evolutionary changes. And so my hope and expectation is that the vaccine’s protection will be robust.