"So far, we can only assume that hypothetically repeated cases of coronavirus infection may occur in people who are affected by two strains at once," Gorelova quoted Interfax as saying.
According to him, the cases of repeated illness are so isolated that no conclusions can be drawn about its possibility.
He noted that the situation with infection with two strains is known from the example of seasonal flu.
The expert also added that such reasons as weakened immunity are possible, and false test results are not excluded.
Earlier, the director of the Gamaleya Center, Alexander Gintsburg, said that the center plans to study secondary immunity to coronavirus infection COVID-19 after vaccination in the future.