Scientists studying the novel coronavirus’s genetic code say it does not appear to be mutating quickly, suggesting any vaccine developed for it will likely remain effective in the long term.

Peter Thielen, a molecular geneticist at the Johns Hopkins University Applied Physics Laboratory, told The Washington Post that there are only about four to 10 genetic differences between the strains infecting people in the U.S. and the virus that emerged in Wuhan, China.

“That’s a relatively small number of mutations for having passed through a large number of people,” he told the newspaper. “At this point the mutation rate of the virus would suggest that the vaccine developed for SARS-CoV-2 would be a single vaccine, rather than a new vaccine every year like the flu vaccine.”

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Thielen compared the eventual vaccine to those used for illnesses such as chickenpox and measles, which generally immunize patients long term.

In contrast, “flu does have one trick up its sleeve that coronaviruses do not have — the flu virus genome is broken up into several segments, each of which codes for a gene,” Benjamin Neuman of Texas A&M University at Texarkana told the Post. “When two flu viruses are in the same cell, they can swap some segments, potentially creating a new combination instantly — this is how the H1N1 ‘swine’ flu originated.”

Small viral mutations leading to outsize effects in clinical outcomes are not unheard of, the experts said, but there has been no indication of such an outcome for the coronavirus thus far, with death rates in places such as Italy likely the result of situational factors rather than mutations.

“So far we don’t have any evidence linking a specific virus [strain] to any disease severity score,” Thielen said. “Right now disease severity is much more likely to be driven by other factors.”