Variants vs. Vaccines

As you are likely aware from media coverage and medical publications, we are at a stage of the pandemic where the rate of coronavirus mutations is inversely related to the rate of immunity in the population, largely achieved through vaccination efforts. On one side, we have a virus that keeps changing, as we would expect. On the other, there are vaccines that largely prevent the virus from infecting cells and having the chance to change. Understanding the virus’s capacity to adapt is a great way to reinforce the importance of vaccination. The faster and more completely we get a large percentage of the population vaccinated, the fewer mutations will occur that allow variants to emerge. Here’s why:

Variants are viruses that have mutated from their original form to express new and different properties, typically consisting of a change in the outer protein structure. The mutations are chance occurrences due to errors in replication. In other words, the cells of a person infected by the virus (host cells) create millions of copies of the virus, and there are mistakes that occur when building the new virus copies.

The mistakes make a virus with a protein that “looks” different. Its outer proteins are angled differently, or they are longer or shorter than those on the original version. These mistakes most often make the new virus not work well, so the virus does not infect cells or replicate in high numbers. Rarely, however, the mistake produces a virus with a structural advantage over the original form. This is the start of a new variant. 

In a basic sense, there are two types of pressures that lead to mutations that allow the virus to proliferate at a rate greater than its predecessor. Sometimes these advantages lead to the emergence of a new dominant strain throughout a population.

• The first one is the pressure to infect. A mutation occurs that allows the virus to more reliably enter a host cell. In other words, the outer protein structure has changed to better attach and go through a channel in the cell membrane. This type of mutation may be the predominant mechanism that allows certain strains to spread more easily.
• The second is the pressure to evade. A mutation occurs that allows the virus to dodge the host immune system, a person’s own immune system fighting the virus. This type of mutation gives rise to strains that can make the person more sick and a vaccine less effective.

Variants are expected, and vaccination reduces the number of variants.

• When most people are vaccinated (including kids), the prevalence of the virus and the amount of viral replication is relatively low, leading to fewer total mutations and variants.
• When most people are not vaccinated, the prevalence of the virus and the amount of viral replication is relatively high, leading to greater total mutations and variants that can keep us on the run for a long time.

Beyond the obvious reasons to get vaccinated—like not getting sick, causing others to become sick, and the desire to shed our masks—vaccination of most everyone is needed to prevent variants from forming and allowing the population to safely return to unrestricted socialization. 

Trey Dobson, MD, is chief medical officer as Southwestern Vermont Medical Center in Bennington.