Thread by @RajeevJayadevan

Study from Cleveland Clinic shows 81.8% lower reinfection rates among those who had prior COVID-19. Those who got reinfection were all mild or asymptomatic. The degree of protection seemed to improve with time.

Details: see thread

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academic.oup.com/cid/advance-ar…

150,435 people were studied. Of these, 8845 had prior COVID-19. In this group, 62 cases of reinfection occurred. That is 0.7%. Half were asymptomatic. None were severe or needed ICU care. No deaths.

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141480 people did not have a history of COVID-19. Among this group, 5449 got COVID-19 during the same time period. That is 3.85%. 60% were symptomatic. No severe cases.

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The calculated difference between infection rates in the 2 groups was 0.7% vs. 3.85% = 81.8%

Not only is there a difference in infection rates between the 2 groups, the testing rates in the past infection group was only half (14%) compared to no prior infection group (28%)

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The chance of a test becoming positive in the prior infection group was only 5%, while it was 14% among those who never had infection previously.

The criteria for testing are not clear, the paper says 40% were done for screening purposes in the second group.

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Hence, it is not exactly an apple to apple comparison. Were people left out of testing as they had prior infection? Did they fail to report symptoms which the second group would have brought to medical attention? Did those who past infection ignore precautions?

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In summary, the available information from this large database from a healthcare system indicates an 81.8% difference between the apparent infection rates in the 2 groups, which may be interpreted as 'protection' due to prior infection. This correlates with other studies.

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