Nothing appears certain
When asked how likely a new strain of SARS-CoV-2 could emerge that gets around vaccine protection, Dr. Nelson said, “I think [what] we’ve learned so far there is no way to predict anything” about this pandemic.
“The best way to prevent the virus from mutating is to prevent hosts, people, from getting sick with it,” he said. “That’s why it’s so important people should get immunized and wear masks.”
Both Dr. Nelson and Dr. Ray pointed out that it is in the best interest of the virus to evolve to be more transmissible and spread to more people. In contrast, a virus that causes people to get so sick that they isolate or die, thus halting transmission, works against viruses surviving evolutionarily.
Some viruses also mutate to become milder over time, but that has not been the case with SARS-CoV-2, Dr. Ray said.
Mutations not the only concern
Viruses have another mechanism that produces new strains, and it works even more quickly than mutations. Recombination, as it’s known, can occur when a person is infected with two different strains of the same virus. If the two versions enter the same cell, the viruses can swap genetic material and produce a third, altogether different strain.
Recombination has already been seen with influenza strains, where H and N genetic segments are swapped to yield H1N1, H1N2, and H3N2 versions of the flu, for example.
“In the early days of SARS-CoV-2 there was so little diversity that recombination did not matter,” Dr. Ray said. However, there are now distinct lineages of the virus circulating globally. If two of these lineages swap segments “this would make a very new viral sequence in one step without having to mutate to gain those differences.”
“The more diverse the strains that are circulating, the bigger a possibility this is,” Dr. Ray said.
Protected, for now
Dr. Walensky’s sober warning came at the same time the CDC released new guidance calling for the wearing of masks indoors in schools and in any location in the country where COVID-19 cases surpass 50 people per 100,000, also known as substantial or high transmission areas.
On a positive note, Dr. Walensky said: “Right now, fortunately, we are not there. The vaccines operate really well in protecting us from severe disease and death.”
A version of this article first appeared on Medscape.com.