William Miller, MD
Updated: Jul 20, 2021
Just when we started to think we were getting on the other side of this COVID pandemic, now we are hearing about it mutating. Is that a cause for concern? I will try to share a perspective, but the quick answer is that such variations are common with all viruses and while they make a very big difference on a global scale, they are less relevant to us as individuals. Here’s why.
Viruses are not capable of replicating themselves. They must infect a host cell and take over its internal machinery, causing the cell to now manufacture virus. In this process, copies of the genetic material of the virus must be made. In fact, hundreds of thousands of copies. New virus proteins are also made and then assembled around the genes to make a new virus particle. In the case of the virus that causes COVID, the whole thing is then covered in a coating of cholesterol. Out of this coat stick proteins referred to as “spikes”. The virus particles then leave the host cell, ready to infect new host cells. These spikes act like a key that fits into a lock on the surface of a potential host cell. The lock is referred to as a receptor.
During the process of mass production of viral genes, mistakes occur frequently. Remember, the cell is not designed for this manufacturing job, but has been pirated to do so by the infecting virus, so errors happen. These mistakes are called mutations. The majority of mutations have no effect upon the virus or the disease it causes one way or another. Many mutations are actually detrimental to the virus and lead to dud viruses that are ineffective. An occasional mutation, however, may turn out to be beneficial to the virus and give it an advantage. This, of course, is how all evolution works for plants, animals and humans.
Most of the variants that we are concerned about have mutations in the spike protein that allows the “key” to fit into the receptor “lock” more efficiently. The result is that these variants are better at gaining access to the interior of the host cell. This means that it takes less of them to infect a person and thus are more contagious. It is important to understand that how these variants spread is not what is changing. The primary way of spread is still respiratory droplets. So, masks, social distancing and hand washing remain effective. In other words, these new variants have not somehow figured out a way to get around your mask or jump further distances.
The most prevalent variant worldwide is G.614 and it is the one that first exhibited a mutation in the spike protein that improved its transmissibility; it is the one that we have been dealing with for most of this pandemic. It is a variant when compared with the original strain in Wuhan, but can be regarded as the “garden variety” one now.
B.1.1.7 is a variant that was first identified in the United Kingdom and is now the dominant strain there. It has been identified in 12 states in the US. The mutation that makes it important also involves the spike protein. As a result, it is about 50% more contagious. Let’s look at exactly what that means. Epidemiologists describe how contagious a virus is by how many people are likely to get infected when someone who has the disease is moving around in society. A lot of factors play into this, but an important thing to remember is that when someone gets infected, they are only contagious for about 10 to 12 days. So, the question then is, “How many close contacts of a contagious person will get infected during that time?” The answer for each virus is a number referred to as R0 (pronounced “R naught”). For COVID, R0 is 2.6, meaning that on average the virus will be spread to 2.6 more people by each person who gets the infection. Masking, social distancing and frequent handwashing drop this to close to zero. Returning to B.1.1.7, a 50% increase in transmissibility increases R0 to 3.9. This has huge implications from a global, epidemiologic perspective. However, for people who are practicing masking, social distancing and handwashing, the change has little consequence.
It does not appear that B.1.1.7 causes any more serious illness and both the Pfizer and Moderna vaccines appear to be quite effective against this strain.
B.1.351 is the one first identified in South Africa. It has the same spike protein mutation as B.1.1.7, meaning that its R0 is the same. However, it has an additional spike mutation near the site where antibodies attach that may make vaccines slightly less effective when considered on a global scale. Studies, so far, have shown that people who got a COVID vaccine and then contract B.1.351 may get ill, but not as sick as those who were unvaccinated.
P.1. (previously referred to as B.1.1.28) is a variant that was first identified in Japan and comprises most of the cases in Brazil. It has both of the spike mutations of B.1.1.7 and B.1.351, plus a third one. It remains unclear how this third mutation will set it apart from the other two strains.
In California, a strain referred to as B.1.427/B.1.429 has caught a lot of attention. We don’t know as much yet about this variant as it was more recently identified. It appears to have accounted for about half the infections in California during the past few months. As with the other variants discussed, it has a mutation on the spike protein that increases its effectiveness. The R0 appears to be about 35% higher than the original strain leading to 0.9 more transmissions per infected person or about 3.5 (versus 2.6). There is debate as to how much this contributed to the large outbreak we saw after Christmas, or how much of that was due to social dynamics of traveling to visit family during the holidays which clearly played a very large role as well. B.1.427 does not appear to cause a more severe illness and both vaccines appear to be effective against it.
In summary, we will continue to see COVID viruses shift into new variants as time goes on. None of these mutations change how the virus is spread, only how well it attaches to the cells in your body if you inhale it. Thus, the same strategies apply to keeping it out of your nose and throat as before. It remains unclear if any of the variants change the severity of illness in any significant way, however, since they all have approximately the same mortality rate suggests that they do not. As for vaccine effectiveness, so far all the different vaccines worldwide do have effectiveness against all of the variants. The question is, will that change significantly with time. We may find that we need to get new updated vaccine shots each year like we do for influenza.