US President Donald Trump claims he is immune to COVID-19 after contracting the virus, but new evidence proves a second infection is possible.
And the second round of symptoms could feel much worse than the first.
The findings were published in The Lancet Infectious Diseases on Monday – the same day Mr Trump declared he was coronavirus free and would pose no risk to infecting others.
“And not only that, it seems like I’m immune, so I can go way out of a basement,” the President told reporters.
“I beat this crazy, horrible China virus … I passed the highest test, the highest standards.
The word ‘immunity’ means something – having a protective glow means something … I’m not on any medication.”
Mr Trump has since continued his re-election campaign, attending a rally in Florida packed by thousands – many without face masks.
But while the President believes he is protected from reinfection, mounting scientific evidence suggests it is possible for a patient to catch the virus twice.
In the new study, American researchers identified the fifth reported case of COVID-19 reinfection in the world.
The case was found in Washoe County, in the US state of Nevada, after a 25-year-old man sought medical help with coronavirus symptoms on three separate occasions.
The patient, who had no pre-existing health conditions, returned his first positive coronavirus test on April 18.
His symptoms included a sore throat, cough, headache, nausea and diarrhoea.
After recovering on April 27, he continued to feel healthy – during which time he returned two negative tests – until the end of May, when the symptoms came back.
Except for this time, they were much worse.
He had a fever, headache, dizziness, cough, nausea and diarrhoea.
The young man attended an urgent care centre, then five days later visited his doctor, where he was rushed to the emergency department and placed on a ventilator.
On June 5, he returned a second positive test.
After analysing the genetic make-up of the patient’s nasal swabs, the researchers found two distinct strains of coronavirus infections, with the second infection’s symptoms much more severe than the first.
And it’s bad news for all of us.
That’s because the possibility of being reinfected with the coronavirus demonstrates “a COVID-19 vaccine may not be totally protective”, said Brendan Wren, a professor of vaccinology at the London School of Hygiene and Tropical Medicine.
However, he added that only five cases of reinfection were “small examples” compared to the “40-plus million cases worldwide”.
Dr Simon Clarke, Associate Professor of Cellular Microbiology at the University of Reading, added that although reinfection might be rare, “it’s equally possible that these could be the first few cases, and that there are many more to come”.
“Initial overconfident predictions that once you’d had it, you couldn’t get it again, were opinions rather than facts,” Dr Clarke said.
“It is becoming increasingly clear that reinfections are possible, but we can’t yet know how common this will be.”
If reinfection is more common than first thought, it would dash any hopes of achieving herd immunity, he said.
“This provides further scientific evidence for extreme caution in proposing policies that allow COVID-19 to rip through the younger population while attempting to shield the elderly and vulnerable – even if that were possible, which it probably isn’t,” he said.