The Covid-19-causing coronavirus is mutating as it spreads around the world in the pandemic, but none of the mutations currently documented appears to be making it able to spread more rapidly, scientists said on Wednesday.
In a study using a global dataset of virus genomes from 46,723 people with Covid-19 from 99 countries, researchers identified more than 12,700 mutations, or changes, in the SARS-CoV-2 virus.
"Fortunately, we found that none of these mutations is making Covid-19 spread more rapidly," said Lucy van Dorp, a professor at University College London's Genetics Institute and one of the co-lead researchers on the study.
She added, however: "We need to remain vigilant and continue monitoring new mutations, particularly as vaccines get rolled out."
Viruses are known to mutate all the time, and some - such as flu viruses - change more frequently than others.
Most mutations are neutral, but some can be either advantageous or detrimental to the virus, and some can make vaccines against them less effective. When viruses change like this, vaccines against them have to be adapted regularly to ensure they are hitting the right target.
With the SARS-CoV-2 virus, the first vaccines to show efficacy against the disease it causes could get regulatory approval and begin to be used to immunise people before the end of the year.
Francois Balloux, a UCL professor who also worked on the study, said that its findings, for now, posed no threat to Covid-19 vaccine efficacy, but cautioned that the imminent introduction of vaccines could exert new selective pressures on the virus to mutate to try to evade the human immune system.
"The news on the vaccine front looks great," he said. "The virus may well acquire vaccine-escape mutations in the future, but we're confident we'll be able to flag them up promptly, which would allow updating the vaccines in time if required.".
The mutation study, preliminary findings of which were originally made public in May as a pre-print before being reviewed by other scientists, was published in full on Wednesday in the peer-reviewed journal Nature Communications.
The research team from Britain's UCL and Oxford University, and from France's Cirad and Université de la Réunion, analysed virus genomes from 46,723 people with Covid-19 from 99 countries, collected up until the end of July 2020.
Among more than 12,706 mutations identified, some 398 appeared to have occurred repeatedly and independently, the researchers said.
Of those, the scientists focused in on 185 mutations which they found had occurred at least three times independently during the course of the pandemic.
The researchers found no evidence that any of the common mutations are increasing the virus's transmissibility. Instead, they said, most common mutations are neutral for the virus.