Associations between SARS-CoV-2 variants and risk of COVID-19 hospitalization among confirmed cases in Washington State: a retrospective cohort study

  1. Miguel I. Paredes
  2. Stephanie M. Lunn
  3. Michael Famulare
  4. Lauren A. Frisbie
  5. Ian Painter
  6. Roy Burstein
  7. Pavitra Roychoudhury
  8. Hong Xie
  9. Shah A. Mohamed Bakhash
  10. Ricardo Perez
  11. Maria Lukes
  12. Sean Ellis
  13. Saraswathi Sathees
  14. Patrick C. Mathias
  15. Alexander Greninger
  16. Lea M. Starita
  17. Chris D. Frazar
  18. Erica Ryke
  19. Weizhi Zhong
  20. Luis Gamboa
  21. Machiko Threlkeld
  22. Jover Lee
  23. Evan McDermot
  24. Melissa Truong
  25. Deborah A. Nickerson
  26. Daniel L. Bates
  27. Matthew E. Hartman
  28. Eric Haugen
  29. Truong N. Nguyen
  30. Joshua D. Richards
  31. Jacob L. Rodriguez
  32. John A. Stamatoyannopoulos
  33. Eric Thorland
  34. Geoff Melly
  35. Philip E. Dykema
  36. Drew C. MacKellar
  37. Hannah K. Gray
  38. Avi Singh
  39. JohnAric M. Peterson
  40. Denny Russell
  41. Laura Marcela Torres
  42. Scott Lindquist
  43. Trevor Bedford
  44. Krisandra J. Allen
  45. Hanna N. Oltean
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Abstract

Background

The COVID-19 pandemic is dominated by variant viruses; the resulting impact on disease severity remains unclear. Using a retrospective cohort study, we assessed the hospitalization risk following infection with seven SARS-CoV-2 variants.

Methods

Our study includes individuals with positive SARS-CoV-2 RT-PCR in the Washington Disease Reporting System with available viral genome data, from December 1, 2020 to January 14, 2022. The analysis was restricted to cases with specimens collected through sentinel surveillance. Using a Cox proportional hazards model with mixed effects, we estimated hazard ratios (HR) for hospitalization risk following infection with a variant, adjusting for age, sex, calendar week, and vaccination.

Findings

58,848 cases were sequenced through sentinel surveillance, of which 1705 (2.9%) were hospitalized due to COVID-19. Higher hospitalization risk was found for infections with Gamma (HR 3.20, 95%CI 2.40-4.26), Beta (HR 2.85, 95%CI 1.56-5.23), Delta (HR 2.28 95%CI 1.56-3.34) or Alpha (HR 1.64, 95%CI 1.29-2.07) compared to infections with ancestral lineages; Omicron (HR 0.92, 95%CI 0.56-1.52) showed no significant difference in risk. Following Alpha, Gamma, or Delta infection, unvaccinated patients show higher hospitalization risk, while vaccinated patients show no significant difference in risk, both compared to unvaccinated, ancestral lineage cases. Hospitalization risk following Omicron infection is lower with vaccination.

Conclusion

Infection with Alpha, Gamma, or Delta results in a higher hospitalization risk, with vaccination attenuating that risk. Our findings support hospital preparedness, vaccination, and genomic surveillance.

Summary

Hospitalization risk following infection with SARS-CoV-2 variant remains unclear. We find a higher hospitalization risk in cases infected with Alpha, Beta, Gamma, and Delta, but not Omicron, with vaccination lowering risk. Our findings support hospital preparedness, vaccination, and genomic surveillance.

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