A “proved” case of a recovered Covid-19 patient who became reinfected has been reported by University of Hong Kong researchers. Read story here. The man did not suffer a relapse; originally infected in Hong Kong in April, he became infected again in August by a different strain after traveling to Spain. Read about that here. Two more cases reinfection have been reported from Europe. Read that story here.
Three cases of reinfection in the entire world might not seem like a big deal. But if reinfection is possible, there’s little to stop other Covid-19 survivors from getting the disease again.
Beyond that, the possibility of reinfection together with other research suggests that the immunity developed from having the disease — or getting a vaccine — wears off, at least in some individuals. This could have major implications for the effectiveness of vaccines and the eventual development of “herd immunity,” in which enough people have become immune to a virus that it stops spreading. Generally speaking, the threshold for this is about 70% of the population.
This suggests vaccines might not be effective after a few months, sufficient herd immunity may never occur, and Covid-19 could be a continuing problem.
Also discouraging is the fact that Covid-19 is a member of the coronavirus family of viruses, and so is the common cold, for which an effective vaccine has never been found.