A Series of Articles on the Science Behind COVID-19
COVID-19 Variants & Vaccines: Why Does a Virus Mutate?
By: Ahmad M. Rashid, MD, pulmonary and critical care physician, National Jewish Health
June 7, 2021
As of April 25, 2021, more than 42% of the U.S. population have received at least one COVID-19 vaccine. Many are asking how effective are the vaccines against the mutant or variant strains of the SARS-CoV-2 virus.
Why does the virus mutate?
Viruses, like all living things, go through mutations throughout their lifespan. If a mutation provides a survival advantage, then that mutated version becomes the dominant strain. Just like the chameleons have evolved to change skin pigment shades to avoid predators, the COVID-19 virus keeps on evolving to avoid its predator – the human immune system.
Virus mutation happens quickly over weeks to months due to the high number of viruses and hosts (people) out there. Since it was first discovered, SARS-CoV2 has been acquiring two mutations in its genome (complete set of DNA) every two weeks. That may sound like a lot, but the influenza virus mutates at a much faster rate.
Do mutations make big changes in a virus?
A mutation is a subtle change in the genes of the virus. Some mutations make the virus more unstable and more vulnerable. Some mutations increase rates of transmission and severity. We become concerned when mutations make the virus more deadly, more contagious or both.
What do the mutations mean?
In a lab, these mutations make the virus more “sticky,” so it binds more tightly with human cells, and is difficult to dislodge. Some mutations in the S. African variant might also make it able to evade the first set of antibodies the immune system uses against it.
What are the main variants right now?
The UK variant, called Alpha, B.1.1.7, has 20 mutations. Some of the mutations increase infectivity, others increase the number of infected cells by helping the virus avoid the immune system.
The South African variant, called Beta, B.1.351, has three mutations, which increase transmission and is only moderately neutralized by monoclonal antibodies.
The P1 variant from Brazil, called Gamma, is similar to South African variant with one extra mutation.
The Delta variant, B.1.617.2, has been blamed for India’s explosive outbreak, is thought to be more transmissible than Alpha since it is a triple mutant.
Do these variants make COVID-19 more contagious?
In the projection models and real-life experience so far, both the U.K. and South African variants seem able to spread more effectively. It is also possible that these strains will become the predominant strains all over the globe.
Are these strains more deadly than SARS-CoV-2?
So far, it does not look like that there is any difference in the disease severity caused by these strains vs. the original SARS-CoV-2 virus. Evidence suggests that the U.K. and South African strains are no more deadly than the original virus. Data indicate that these variants may be more difficult to “neutralize” by the immune system, or with monoclonal antibodies or convalescent plasma.
Do the vaccines protect us against these new variants?
So far, the studies have shown that the mutations have not changed the “big picture” of the virus, so that the immune system can still recognize the actual virus and act against it even if there are mutations.
In the last month multiple studies have shown that, all available vaccines can neutralize variants in the lab. Real-life data show that the vaccines, even with the variants, provide a very high degree of protection against mild or moderate disease, and dramatically reduce the risk of severe disease and death even.
Bottom Line:
The vaccines work well against the virus and variants. New strains can be stopped by widespread vaccination. This has been shown in Israel where some 54% of the population has been vaccinated, positive virus test rates are just 0.2% and the economy has reopened.
In the meantime, as life slowly returns to normal and summer approaches, we should all:
- Get the vaccine as soon as possible
- Still wear a mask indoors for now
- Limit large indoor gatherings with poor ventilation
- Keep washing our hands
- Protect the vulnerable