This evidence review was compiled by members of the CITF Secretariat with the input from experts affiliated with the CITF and does not necessarily reflect the views of all CITF members.

New research out of England published in The Lancet Infectious Diseases suggests that hospitalization and visits to the emergency department are twice as likely with the variant of concern (VOC) Delta compared to the Alpha variant. These findings come at a time when Delta is surging worldwide, forewarning its significant strain on healthcare systems.

The study included more than 8,000 individuals infected with the VOC Delta as well as more than 34,000 infected with the Alpha variant, between March 29 and May 23, 2021. Vaccination, hospital attendance, and mortality data were compiled.

Key findings:

  • Infections caused by the Delta variant were found to double the risk of hospitalization or visits to the emergency department compared to the Alpha variant.
  • Importantly, the authors observed that, among non-vaccinated individuals, those infected with the Delta variant were approximately twice as likely to be hospitalized than those infected with the Alpha variant; though, it should be noted that due to the timing of the study, most participants had not yet been offered vaccination.

Twohig KA, Nyberg T, Zaidi A, Thelwall S, Sinnathamby MA, Aliabadi S, Seaman SR, Harris RJ, Hope R, Lopez-Bernal J, Gallagher E, Charlett A, De Angelis D, the COVID-19 Genomics UK (COG-UK) consortium, Presanis AM, Dabrera G. Hospital admission and emergency care attendance risk for SARS-CoV-2 delta (B.1.617.2) compared with alpha (B.1.1.7) variants of concern: a cohort study. Lancet Infect Dis. 2021 Aug 27. doi: 10.1016/S1473-3099(21)00475-8