Coronavirus vaccines could cause the virus to mutate, meaning new forms of jab would need to be created, scientists have said.
Researchers at University College London (UCL) warned that the world needs to remain vigilant for genetic changes to Sars-Cov-2, the virus that causes Covid-19.
They said the imminent introduction of vaccines may "exert new selective pressures on the virus" that could lead to mutations that do not respond to jabs.
Their comments are based on analysis of genetic material from more than 46,000 people with Covid-19 from 99 countries.
First author Lucy Van Dorp, of the UCL Genetics Institute, said: "Fortunately, we found that none of these mutations are making Covid-19 spread more rapidly, but we need to remain vigilant and continue monitoring new mutations, particularly as vaccines get rolled out."
Mutations in coronaviruses can occur as a result of copying errors as the virus replicates itself inside the body, through interactions with other viruses infecting the same cell or through changes introduced by the host's immune system.
The new study, published in the journal Nature, follows a scare earlier this month when Sars-Cov-2 was shown to have mutated after jumping to mink in Denmark.
Lead author Professor Francois Balloux, also of the UCL Genetics Institute, said: "The news on the vaccine front looks great. 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 UCL team, along with experts from Cirad, Universite de la Reunion and the University of Oxford, analysed a global dataset of Sars-Cov-2 genomes from 46,723 people, collected up until the end of July 2020.
The teams have so far identified 12,706 mutations in Sars-Cov-2, and said there is strong evidence that mutations have occurred repeatedly and independently in 398 of the cases.
Based on a modelling of the evolutionary tree of the virus, the scientists said they found no evidence any of the common mutations are increasing transmissibility.