This question has been on the lips of many as different countries are reopening the economy gradually.
However, the key question should not be if someone could be reinfected, instead it should be “Whether antibodies produced by the body following an infection with the coronavirus provide some level of immunity, and if so, for how long”.
But we do have some clues:
“We know from ‘normal’ coronavirus studies done in the past you can infect people after about a year following an initial infection,” said Dr Ben Killingley, consultant in acute medicine and infectious diseases at University College London hospital.
Dr Joshua Schiffer, an expert in infectious diseases at Fred Hutchinson Cancer Research Center in the US, added that any signs of reinfection would require detailed scrutiny.
“I have yet to see a definitive case of reinfection reported in the scientific literature [to date]. To truly prove reinfection, and discriminate from prolonged viral shedding related to the first infection, would require sequencing of both the first and second viruses and demonstration that the two viruses are genetically different,” he said, adding it will also be important to look at symptoms and how long reinfection lasts.
“It is also important to recognise that documentation of one or a handful of reinfections does not prove that this is a common, epidemiologically important event.”
According to the World Health Organisation, people who recover from COVID-19 develop antibodies in their blood. But some people appear to have low levels of neutralising antibodies.
To see if an antibody is a neutralising antibody, you need to do special laboratory tests to see the effect of the antibody in cells exposed to the virus.
But even if an antibody blood test could confirm neutralising antibodies, it doesn’t automatically mean the person is immune from further infection. Even though the antibody is present, for example, the quantities may be insufficient to work.
So a positive antibody blood test to COVID-19 doesn’t confirm if someone is immune to COVID-19 or not. It only tells us if a person has ever been exposed to COVID-19 – and even that depends on how sensitive and specific the antibody test is.
Moreover, there are reports from different countries of people hospitalised with COVID-19 who tested negative when they were discharged, before testing positive again.
However, a study from China found those who retested positive didn’t get any sicker. This suggests these people were intermittently shedding the virus and were at the tail end of their original illness, rather than getting a new COVID-19 infection.
The nasal and throat swab test being used to detect the virus also can’t say whether the virus is alive or not; therefore, they could have just been shedding dead virus. This could explain why their close contacts didn’t become sick or test positive.