Dr Anders Tegnell, who has guided the nation through the pandemic without calling for a lockdown, says he hasn’t seen evidence of people getting infected twice since the start of the pandemic in December 2019.
Even if a survivor doesn’t develop antibodies — immune cells that remember how to fight the virus — they will be protected, he believes.
Evidence is starting to show that antibodies aren’t the only type of immunity against Covid-19, and that T cells also play an important role.
It’s hoped T cells, which target and destroy cells already infected, would offer long-term protection — possibly up to many years later.
But scientists do not have any firm proof as to how long immunity actually lasts once a person has fought off Covid-19, mainly because it is still shrouded in secrecy and has only been known to exist since the start of the year.
There have been cases of people getting infected more than once but they have failed to convinced scientists that humans only get a short-lived immunity against the disease.
Some infectious disease experts say it is just an issue with testing because old viral fragments that are not contagious are picked up by swabs taken weeks or months after a patient first became ill.