Assessment of the risk of SARS-CoV-2 reinfection in an intense re-exposure setting

Abu-Raddad, L. J.; Chemaitelly, H.; Ayoub, H. H.; Al Kanaani, Z.; Al Khal, A.; Al Kuwari, E.; Butt, A. A.; Coyle, P.; Jeremijenko, A.; Kaleeckal, A. H.; Latif, A. N.; Abdul Rahim, H. F.; Al Kuwari, M. G.; Al Romaihi, H. E.; Al Thani, S. M.; Bertollini, R.

Background: Reinfection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has been a subject of debate. We aimed to assess the risk and incidence rate of documented SARS-CoV-2 reinfection in a large cohort of laboratory-confirmed cases in Qatar. Methods: All SARS-CoV-2 laboratory-confirmed cases with at least one PCR positive swab that is [≥]45 days after a first positive swab were individually investigated for evidence of reinfection, and classified as showing strong, good, some, or weak/no evidence for reinfection. Risk and incidence rate of reinfection were estimated. Results: Out of 133,266 laboratory-confirmed SARS-CoV-2 cases, 243 persons (0.18%) had at least one subsequent positive swab [≥]45 days after the first positive swab. Of these, 54 cases (22.2%) had strong or good evidence for reinfection. Median time between first and reinfection swab was 64.5 days (range: 45-129). Twenty-three of the 54 cases (42.6%) were diagnosed at a health facility suggesting presence of symptoms, while 31 (57.4%) were identified incidentally through random testing campaigns/surveys or contact tracing. Only one person was hospitalized at or following time of reinfection swab, but still had relatively mild infection. No deaths were recorded. Risk of reinfection was estimated at 0.04% (95% CI: 0.03-0.05%) and incidence rate of reinfection was estimated at 1.09 (95% CI: 0.84-1.42) per 10,000 person-weeks. Conclusions: SARS-CoV-2 reinfection appears to be a rare phenomenon suggestive of a strong protective immunity against reinfection that lasts for at least a few months post primary infection.