COVID-19 variants: Infectious disease expert available for interviews
SARS-CoV-2, the virus that causes COVID-19, has been mutating from the onset of the pandemic.
COVID-19 is an RNA virus, which means that the genetic material for SARS-CoV-2 is encoded in ribonucleic acid (RNA). The viral RNA can enter human cells and hijack our cell’s machinery to copy itself, potentially making us sick and contagious to others where the replication cycle can start again.
Each time the virus replicates is an opportunity for minor changes: Envision writing an essay without spellcheck leaving room for typos to occur in each sentence.
“A mutation is a change in the genetic sequence of the virus,” says Marie Landry, MD, Clinical Virology Laboratory, Yale New Haven Hospital. “When a virus replicates, it makes numerous copies of its genome to create new virus particles. Small errors can occur that change the genetic sequence, especially in RNA viruses due to their error-prone RNA polymerases (the enzyme that makes copies of their genomes) and their poor ‘proof reading’ functions.”
Most of these mutations happen by chance and have little or no effect on how the virus will impact its hosts. However, sometimes a mutation or combination of mutations will produce a variant with an advantage over other variants, causing it to be the dominate iteration of the virus in that particular area with the ability to expand its reach.
Reports of mutations that give the virus an advantage, such as the UK variant, have emerged along with questions around how these mutations will impact immunity either via natural infection or vaccination.
When examining a new virus variant, researchers focus on pace of transmission, severity and immunity.
“The variants that have been identified in the UK, South Africa and Brazil all have similar mutations in the spike protein that appear to make these variants more transmissible,” said Richard Martinello, MD, medical director, Infection Prevention, Yale New Haven Health.
Dr. Martinello points out that these variants spread the same way as the virus we saw in late 2019, which is why masking and distancing is still effective. What makes these variants more contagious is their ability to enter human cells after an exposure.
As of the first half of January 2021, none of the variants seem to increase how sick infected people get.
The spike protein on the surface of SARS CoV-2 is the target of current vaccines. With that in mind, mutations on the spike protein are of greatest concern.
Dr. Landry said, “When a new variant of concern is identified, scientists investigate whether antibodies induced by vaccination are still effective in neutralizing the new virus variant in the laboratory.”
In January 2021, a laboratory-based study by Pfizer and BioNTech showed that the mRNA vaccine is likely effective against the variant first identified in the UK.
Of this study, Dr. Martinello said “There is still plenty of room for more research, however we have every reason to think the vaccine will be equally effective against this variant.”
These mRNA vaccines were designed to account for some mutations with something called a polyclonal response. This means the vaccine prompts the body to generate antibodies that can target different parts of the spike protein on the virus.
Even if the virus accumulates enough mutations to reduce vaccine efficacy, getting the vaccine will still prevent many people from being hospitalized and suffering long term consequences of COVID-19.
In the event that the new variants can evade antibodies created as a result of the vaccine, mRNA vaccine technology can be leveraged to respond to these changes.
Dr. Landry emphasized that the longer we take to vaccinate everyone, the more the virus can mutate which could impact not only vaccine efficacy but diagnostic testing and treatments.
“Indeed, the recent variants of concern were discovered in areas with high levels of COVID-19 infection,” Dr. Landry said.
While Dr. Landry shares that halting all mutations would require eliminating the virus from circulation completely, as we did with smallpox in the 1970’s and hope to do with poliovirus, mass COVID-19 vaccination will decrease the virus’ opportunities to mutate.