Different strains of the coronavirus will likely reinfect people every few years, according to a British medical expert.

Paul Hunter, professor of medicine at the University of East Anglia, predicts more variants of the virus could emerge even as the pandemic ends, according to a recent report.

The World Health Organization has identified three variants of the coronavirus, including the South Africa and Brazil strains, which experts say could be resistant to vaccines.

Hunter said it was “difficult to predict” how COVID will mutate, adding new strains might not lead to serious illness.

Still, in an interview with BBC Radio 4, he urged governments to be vigilant as they reopen economies.

“We do know that new variants develop, that’s very obvious, and some new variants spread and become dominant,” he said. “Many new variants just die out. … Ultimately with the other human coronaviruses, we expect to get reinfected on average every two to four years with the same virus.”