How long does coronavirus immunity last?

The first cases of reinfection are emerging in Hong Kong, the United States and Europe. There is growing evidence that immunity to the new coronavirus after infection may be short-lived. Following reports in Hong Kong that a man had contracted the virus for a second time just over four months, experts are now saying there is likely only a slim possibility of people being re-infected with COVID-19, but nobody knows for sure. They suggest immunity from the disease does not necessarily last long. So much for herd immunity, or full immunity. Concrete answers are vital in developing a vaccine, that is, if we ever get one. 

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