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. 2024 Sep 6;19(9):e0309645.
doi: 10.1371/journal.pone.0309645. eCollection 2024.

Evaluating the risk of SARS-CoV-2 reinfection with the Omicron or Delta variant in Wales, UK

Mark Postans  1 , Nicole Pacchiarini  1 , Jiao Song  1 , Simon Cottrell  1 , Catie Williams  2 , Andrew Beazer  2 , Catherine Moore  3 , Thomas R Connor  2   4 , Christopher Williams  1
Affiliations

Evaluating the risk of SARS-CoV-2 reinfection with the Omicron or Delta variant in Wales, UK

Mark Postans et al. PLoS One. .

Abstract

Recent studies suggest an increased risk of reinfection with the SARS-CoV-2 Omicron variant compared with previous variants, potentially due to an increased ability to escape immunity specific to older variants, high antigenic divergence of Omicron from earlier virus variants as well as its altered cell entry pathway. The present study sought to investigate epidemiological evidence for differential SARS-CoV-2 reinfection intervals and incidence rates for the Delta versus Omicron variants within Wales. Reinfections in Wales up to February 2022 were defined using genotyping and whole genome sequencing. The median inter-infection intervals for Delta and Omicron were 226 and 192 days, respectively. An incidence rate ratio of 2.17 for reinfection with Omicron compared to Delta was estimated using a conditional Poisson model, which accounted for several factors including sample collection date, age group, area of residence, vaccination and travel status. These findings are consistent with an increased risk of reinfection with the Omicron variant, and highlight the value of monitoring emerging variants that have the potential for causing further waves of cases.

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Conflict of interest statement

The authors have declared that no competing interests exist.

Figures

Fig 1
Fig 1. Weekly positive samples sequenced by WHO classification label (stacked bars) and the log-transformed number of cases in Wales (gray shaded area).
A total of 251,329 positive samples were sequenced or genotyped over the study period.
Fig 2
Fig 2. Rolling 7-day average number of samples by sample date and infection type.
Fig 3
Fig 3. Mosaic plot of the number of reinfections by first infection and second infection variant.
The area of each tile is proportional to the corresponding contingency table cell count in Table 1. The vertical height of each tile in the first (second) column reflects the proportion of Delta (Omicron) reinfections that were associated with an initial Wuhan-Hu-1, Alpha, Delta or Omicron infection. The tile shading represents the magnitude and sign of the Pearson residual for the cell of the associated contingency table. Red indicates a cell with fewer cases than expected whereas blue indicates a cell with more cases than expected under the null model.
Fig 4
Fig 4. First-to-second COVID infection interval by second infection variant.
Stacked and un-stacked histograms (left and right, respectively).
See this image and copyright information in PMC

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Supplementary concepts