Is COVID-19 Reinfection Possible?
Deliberately infecting a human with a low dose of virus has not been done enough for there to be research literature about it.
But what happens when we do it with animals?
We have mixed results on reinfection in animals, with some studies showing that prior exposure to a coronavirus protects against subsequent infection, while others showed that reinfection can indeed occur.
Rhesus monkeys that have been infected with SARS-CoV-2 do not get reinfected after a second challenge; they do not show viral replication or clinical symptoms.
Mice who have previously been exposed to SARS-CoV are protected from disease for at least 28 days. Serum from mice that had previously been exposed to the virus, injected into SARS-naive mice, also had a protective effect, while serum from non-exposed mice did not.
Ferrets infected with SARS-CoV who were reinfected 4 weeks later did not have as high viral titers upon reinfection and did not show lung histopathology.
Alpacas and camels experimentally infected with MERS-CoV are protected against reinfection. On the other hand, a longitudinal study of a camel herd showed that reinfection can occur in camels who have previously acquired antibodies to MERS-CoV.
Reinfection is possible in cats previously exposed to feline coronavirus , and in cows with bovine coronavirus .
Exposure to an inactivated form of a virus is a standard type of vaccine, and it has been found effective in rodents for SARS-CoV.
Partially inactivated SARS-CoV virus samples (treated with formaldehyde) were no longer able to replicate in vitro.
When mice were treated with this inactivated virus (by injection or intranasal administration) they produced detectable antibody responses. SARS-CoV virus inactivated with UV radiation also produced an antibody response in mice.
Whole killed SARS-CoV vaccine (inactivated with beta-propiolactone) protected mice against a challenge infection.
Hamsters immunized with beta-propiolactone inactivated SARS-CoV virus had lower virus titers than non-immunized hamsters upon challenge with active SARS-CoV and had less severe lung lesions than non-immunized hamsters.
There have been reports of reinfected COVID-19 patients in China and Japan but some think that these are due to testing errors where the patients erroneously tested as having recovered when they were still infected.
The current state of evidence hasn’t ruled out that reinfection could occur for SARS-CoV-2, but tentatively it seems more likely that people who have been infected once are protected against further infections for some period of time. The duration of protection, and whether there are any individuals who don’t get immunological protection, is still unknown.
In conclusion, there’s reason to believe that exposure to a lower dose of the SARS-CoV-2 virus produces a milder disease than exposure to larger quantities of SARS-CoV-2.
In addition, there’s reason to believe that people who have recovered from COVID-19 have some protection against the disease.
What we don’t know is whether a dose low enough not to cause severe symptoms is also high enough to cause immune protection against subsequent infections.
Written by Sarah Constantin, Edited by Michael Ding & Alexander Fleiss
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