Diagnostics (Mar 2022)

The Effect of Varying Interval Definitions on the Prevalence of SARS-CoV-2 Reinfections: A Retrospective Cross-Sectional Cohort Study

  • Sjoerd M. Euser,
  • Tieme Weenink,
  • Jan M. Prins,
  • Milly Haverkort,
  • Irene Manders,
  • Steven van Lelyveld,
  • Bjorn L. Herpers,
  • Jan Sinnige,
  • Jayant Kalpoe,
  • Dominic Snijders,
  • James Cohen Stuart,
  • Fred Slijkerman Megelink,
  • Erik Kapteijns,
  • Jeroen den Boer,
  • Alex Wagemakers,
  • Dennis Souverein

DOI
https://doi.org/10.3390/diagnostics12030719
Journal volume & issue
Vol. 12, no. 3
p. 719

Abstract

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Background: We assessed the SARS-CoV-2 reinfection rate in a large patient cohort, and evaluated the effect of varying time intervals between two positive tests on assumed reinfection rates using viral load data. Methods: All positive SARS-CoV-2 samples collected between 1 March 2020 and 1 August 2021 from a laboratory in the region Kennemerland, the Netherlands, were included. The reinfection rate was analyzed using different time intervals between two positive tests varying between 2 and 16 weeks. SARS-CoV-2 PCR crossing point (Cp) values were used to estimate viral loads. Results: In total, 679,513 samples were analyzed, of which 53,366 tests (7.9%) were SARS-CoV-2 positive. The number of reinfections varied between 260 (0.52%) for an interval of 2 weeks, 89 (0.19%) for 4 weeks, 52 (0.11%) for 8 weeks, and 37 (0.09%) for a minimum interval of 16 weeks between positive tests. The median Cp-value (IQR) in the second positive samples decreased when a longer interval was chosen, but stabilized from week 8 onwards. Conclusions: Although the calculated reinfection prevalence was relatively low (0.11% for the 8-week time interval), choosing a different minimum interval between two positive tests resulted in major differences in reinfection rates. As reinfection Cp-values stabilized after 8 weeks, we hypothesize this interval to best reflect novel infection rather than persistent shedding.

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