Russia's plan to roll-out coronavirus vaccine could encourage the virus to mutate, experts warn

Experts have warned Russia's plan to roll-out its "Sputnik-V" coronavirus vaccine before it has been fully trialled could encourage the virus to mutate.

Viruses such as Covid-19 often mutate frequently, which can have little to no risk on their impact to people.

But some scientists are worried that a partially effective vaccine may encourage the virus to mutate by adding "evolutionary pressure" to it.

"Less than complete protection could provide a selection pressure that drives the virus to evade what antibody there is, creating strains that then evade all vaccine responses," said Ian Jones, a virology professor at Reading University.

"In that sense, a poor vaccine is worse than no vaccine."

Sputnik-V's developers, as well as financial backers and Russian authorities, say the vaccine is safe, citing two months of small-scale human trials which they say show that it works.

However, the results of those trials have not been made public, and many Western scientists are warning against its use until all it has passed internationally approved testing and regulatory hurdles.

Russia said on Thursday it plans to begin a large-scale efficacy trial of the vaccine in a total of 40,000 people, but will also begin administering it to people in high-risk groups, such as healthcare workers, before the trial has produced any results.

"You want to make sure the vaccine is effective. We really don't know that (about the Sputnik vaccine)," said Kathryn Edwards, a professor of paediatrics and vaccine expert in the infectious diseases division at Vanderbilt University School of Medicine in the United States.

She described the risk of what a vaccine might do to a virus as "always a concern".

Dan Barouch, a specialist at Harvard's Beth Israel Deaconess Medical Center in Boston, said mutation rates for coronaviruses are far lower than for viruses like HIV, but added: "There are many potential downsides of using a vaccine that doesn't work. The risk that it (the virus) would mutate is a theoretical risk."

Bacterial pathogens face similar evolutionary pressure to mutate when faced with antibiotics designed to target them, and can evolve and adapt to evade the drugs and develop resistance, scientists say.

The World Health Organisation says antibiotic resistance and the rise of superbugs is one of the biggest threats to global health, food security and development today.

Dr Jones emphasised that vaccine-induced viral mutations are "a rare outcome". He said the greater the efficacy of the vaccine in blocking a virus' ability to enter cells and replicate there, the lower the risk of it having an opportunity to learn how to evade antibody defences.

"If (a vaccine) is completely sterilising, the virus can't get in, so it can't learn anything because it never gets a chance," he said. "But if it gets in and replicates ... there is selection pressure for it to evade whatever antibodies have been generated by the inefficient vaccine. And you don't know what the outcome of that will be."

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