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SARS-CoV-2 reinfection trends in South Africa: analysis of routine surveillance data (preprint)
medrxiv; 2021.
Preprint
in English
| medRxiv | ID: ppzbmed-10.1101.2021.11.11.21266068
ABSTRACT
Objective:
To examine whether SARS-CoV-2 reinfection risk has changed through time in South Africa, in the context of the emergence of the Beta and Delta variantsDesign:
Retrospective analysis of routine epidemiological surveillance dataSetting:
Line list data on SARS-CoV-2 with specimen receipt dates between 04 March 2020 and 30 June 2021, collected through South Africa's National Notifiable Medical Conditions Surveillance SystemParticipants:
1,551,655 individuals with laboratory-confirmed SARS-CoV-2 who had a positive test result at least 90 days prior to 30 June 2021. Individuals having sequential positive tests at least 90 days apart were considered to have suspected reinfections. Main outcomemeasures:
Incidence of suspected reinfections through time; comparison of reinfection rates to the expectation under a null model (approach 1); empirical estimates of the time-varying hazards of infection and reinfection throughout the epidemic (approach 2)Results:
16,029 suspected reinfections were identified. The number of reinfections observed through the end of June 2021 is consistent with the null model of no change in reinfection risk (approach 1). Although increases in the hazard of primary infection were observed following the introduction of both the Beta and Delta variants, no corresponding increase was observed in the reinfection hazard (approach 2). Contrary to expectation, the estimated hazard ratio for reinfection versus primary infection was lower during waves driven by the Beta and Delta variants than for the first wave (relative hazard ratio for wave 2 versus wave 1 0.75 (95% CI 0.59-0.97); for wave 3 versus wave 1 0.70 (95% CI 0.55-0.90)). Although this finding may be partially explained by changes in testing availability, it is also consistent with a scenario in which variants have increased transmissibility but little or no evasion of immunity.Conclusion:
We conclude there is no population-wide epidemiological evidence of immune escape and recommend ongoing monitoring of these trends.
Full text:
Available
Collection:
Preprints
Database:
medRxiv
Language:
English
Year:
2021
Document Type:
Preprint
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