Local media have reported that two people in Europe have been reinfected with coronavirus.
The shocking findings have been described as "not good news" by experts who have been left shocked by the discoveries in Belgium and the Netherlands
Dutch broadcaster NOS revealed that one of the reinfected patients was an elderly person with a weakened immune system.
Officials said the Belgian patient has "mild" symptoms, while no further information was provided on the Dutch patient.
Belgian virologist Mark Van Ranst said the antibodies produced during the first infection were not able to deal with a second, different strain of Covid-19.
He told the Terzake programme: "There are indeed enough differences to be able to speak of a different strain, a second infection.
"It is not good news. You hope you are out of harm's way. Hopefully that is the case in most cases."
It comes after scientists revealed yesterday that a "young and healthy" man was found to have been reinfected in Hong Kong.
The first case of someone being reinfected with coronavirus was reported by researchers after a study at the University of Hong Kong's (HKU) department of microbiology.
It says that an "apparently young and healthy patient had a second episode of Covid-19 infection which was diagnosed 4.5 months after the first episode".
The scientists say the case illustrates that reinfection can occur a few months after recovery from the first infection.
The findings indicate the disease, which has killed more than 800,000 people worldwide, will continue to spread among the global population despite herd immunity, they said.
The 33-year-old male was cleared of Covid-19 and discharged from a hospital in April, but tested positive again after returning from Spain via the UK on August 15.
The patient had appeared to be previously healthy, researchers said in the paper, which was accepted by the international medical journal Clinical Infectious Diseases.
He was found to have contracted a different coronavirus strain from the one he had previously contracted and remained asymptomatic for the second infection.
