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

By K. Twohig, T. Nyberg, A. Zaidi, S. Thelwall, M. Sinnathamby, S. Aliabadi, S. Seaman, Ross J. Harris, R. Hope, J. Lopez-Bernal and 595 more. Lancet. Infectious Diseases (Print), 2021

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Background The SARS-CoV-2 delta (B.1.617.2) variant was first detected in England in March, 2021. It has since rapidly become the predominant lineage, owing to high transmissibility. It is suspected that the delta variant is associated with more severe disease than the previously dominant alpha (B.1.1.7) variant. We aimed to characterise the severity of the delta variant compared with the alpha variant by determining the relative risk of hospital attendance outcomes. Methods This cohort study was done among all patients with COVID-19 in England between March 29 and May 23, 2021, who were identified as being infected with either the alpha or delta SARS-CoV-2 variant through whole-genome sequencing. Individual-level data on these patients were linked to routine health-care datasets on vaccination, emergency care attendance, hospital admission, and mortality (data from Public Health England's Second Generation Surveillance System and COVID-19-associated deaths dataset; the National Immunisation Management System; and NHS Digital Secondary Uses Services and Emergency Care Data Set). The risk for hospital admission and emergency care attendance were compared between patients with sequencing-confirmed delta and alpha variants for the whole cohort and by vaccination status subgroups. Stratified Cox regression was used to adjust for age, sex, ethnicity, deprivation, recent international travel, area of residence, calendar week, and vaccination status. Findings Individual-level data on 43 338 COVID-19-positive patients (8682 with the delta variant, 34 656 with the alpha variant; median age 31 years [IQR 17–43]) were included in our analysis. 196 (2·3%) patients with the delta variant versus 764 (2·2%) patients with the alpha variant were admitted to hospital within 14 days after the specimen was taken (adjusted hazard ratio [HR] 2·26 [95% CI 1·32–3·89]). 498 (5·7%) patients with the delta variant versus 1448 (4·2%) patients with the alpha variant were admitted to hospital or attended emergency care within 14 days (adjusted HR 1·45 [1·08–1·95]). Most patients were unvaccinated (32 078 [74·0%] across both groups). The HRs for vaccinated patients with the delta variant versus the alpha variant (adjusted HR for hospital admission 1·94 [95% CI 0·47–8·05] and for hospital admission or emergency care attendance 1·58 [0·69–3·61]) were similar to the HRs for unvaccinated patients (2·32 [1·29–4·16] and 1·43 [1·04–1·97]; p=0·82 for both) but the precision for the vaccinated subgroup was low. Interpretation This large national study found a higher hospital admission or emergency care attendance risk for patients with COVID-19 infected with the delta variant compared with the alpha variant. Results suggest that outbreaks of the delta variant in unvaccinated populations might lead to a greater burden on health-care services than the alpha variant. Funding Medical Research Council; UK Research and Innovation; Department of Health and Social Care; and National Institute for Health Research.

Subfields: Infectious Diseases, Modeling and Simulation, Neurology

View Paper: https://www.semanticscholar.org/paper/168100385359ef88bf059fa1deca4de06432433e

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Citations in the corpus

Global impact of the first year of COVID-19 vaccination: a mathematical modelling study (2022, neutral): “20,21 Any epidemiological differences associated with previous variants were assumed to be reflected by their effects on mortality, 22 which were subsequently captured by the estimated R t trend.”
Attenuated fusogenicity and pathogenicity of SARS-CoV-2 Omicron variant (2022, positive): “Furthermore, whereas the greater severity of COVID-19 and unusual symptoms that are caused by Delta infection have been well documented 35–37 , a reduced risk of severe COVID-19 in individuals who are infected with Omicron compared to those infected with Delta has been recently reported 38 .”
Comparing COVID-19 vaccines for their characteristics, efficacy and effectiveness against SARS-CoV-2 and variants of concern: a narrative review (2021, positive): “Most observational studies assessed the mRNA vaccines, CoronaVac and AZD1222 which appear to be safe and highly effective tools to prevent severe disease, hospitalization and death against all variants of concern (Alpha, Beta, Gamma and Delta).”
Early computational detection of potential high-risk SARS-CoV-2 variants (2021, background): “The Delta (B.1.617.2, AY) variant – characterised by high transmissibility – led to increased mortality and triggered a renewed increase in cases in countries with both high and low vaccination rates such as the United Kingdom [5] and India [6].”