Scientists have looked at six other human coronaviruses for some indication, where four produce the symptoms of the common cold and immunity is short-lived.
Studies showed some patients could be reinfected within a year. Formerly, the only cases where someone has tested positive, then negative, then positive again has been down to inaccuracies with testing.Nobody has been deliberately reinfected with the virus to test immunity, but a pair of rhesus macaque monkeys have.They were infected twice, once to build up an immune response and then a second time three weeks later.
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