Past COVID-19 infection provides some immunity but people may still carry and transmit virus

Researchers working on the SIREN study have concluded naturally acquired immunity as a result of past infections provide 83% protection against reinfection, compared to people who have not had disease before, which appears to last at least for 5 months from first becoming sick.

SPS commentary:

Public Health England’s SIREN (SARS-CoV-2 Immunity and Reinfection EvaluatioN) study has performed regular antibody and PCR testing on 20,787 healthcare workers, including frontline clinical staff and those in non-clinical roles, from 102 NHS trusts since the study commenced in June. 6,614 of these participants tested positive for COVID-19 antibodies upon recruitment. While the SIREN study will continue to assess whether protection may last for longer, the researchers suggest current findings mean people who contracted the disease in the first wave may now be vulnerable to catching it again.

Public Health England