Increased risk of hospitalisation and death with the delta variant in the USA

Abstract

Increased hospitalisation risk with SARS-CoV-2 delta (B.1.617.2) variant infection compared with alpha (B.1.1.7) variant infection in unvaccinated people was reported by Katherine Twohig and colleagues in the UK (hazard ratio [HR] 2·32 [95% CI 1·29–4·16])1Twohig KA Nyberg T Zaidi A et al.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; (published online Aug 27.)https://doi.org/10.1016/S1473-3099(21)00475-8Summary Full Text Full Text PDF PubMed Scopus (278) Google Scholar and Peter Bager and colleagues in Denmark (3·01 [2·02–4·50]).2Bager P Wohlfahrt J Rasmussen M Albertsen M Krause TG Hospitalisation associated with SARS-CoV-2 delta variant in Denmark.Lancet Infect Dis. 2021; 211351Summary Full Text Full Text PDF Scopus (23) Google Scholar To corroborate these results in the USA, as well as to examine risk of intensive care unit (ICU) admission or death, we analysed a large cohort of unvaccinated COVID-19 cases within the Veterans Health Administration (VHA) using the previously described COVID-19 Shared Data Resource.3Butt AA Yan P Shaikh OS Mayr FB Outcomes among patients with breakthrough SARS-CoV-2 infection after vaccination in a high-risk national population.EClinicalMedicine. 2021; 40101117Summary Full Text Full Text PDF PubMed Scopus (14) Google Scholar In the absence of available genomic confirmation of SARS-CoV-2 variant, we used two time periods: the first before substantial delta variant detection in the USA (Feb 1–May 15, 2021) and the second with clear dominance by the delta variant (July 10–Aug 31, 2021).4Centers for Disease Control and PreventionCOVID Data Tracker.https://covid.cdc.gov/covid-data-trackerDate accessed: September 2, 2021Google Scholar Patient characteristics are described in the appendix. During the delta surge, patients were more likely to be younger and female, and there were lower rates of comorbidities. Comparing delta and pre-delta timeframes, and adjusting for age, race, ethnicity, gender, body-mass index, diabetes, hypertension, chronic obstructive pulmonary disease, cardiovascular disease, and kidney disease, there was a significant increase in the risk of hospitalisation (HR 1·93 [95% CI 1·84–2·03]), ICU stay (odds ratio 2·29 [2·12–2·47]), and death (HR 2·15 [1·93–2·39]). Stratifying by age (<50 years vs ≥50 years), we found that although not statistically different, the increase in risk of death with the delta variant seemed higher for those younger than 50 years (HR 3·31 [2·05–5·34]) than those aged 50 years and older (2·09 [1·88–2·34]). These results show that in a population of unvaccinated VHA patients, infection with the delta variant conferred an approximately two-fold increased risk of hospitalisation, consistent with previous studies.1Twohig KA Nyberg T Zaidi A et al.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; (published online Aug 27.)https://doi.org/10.1016/S1473-3099(21)00475-8Summary Full Text Full Text PDF PubMed Scopus (278) Google Scholar, 2Bager P Wohlfahrt J Rasmussen M Albertsen M Krause TG Hospitalisation associated with SARS-CoV-2 delta variant in Denmark.Lancet Infect Dis. 2021; 211351Summary Full Text Full Text PDF Scopus (23) Google Scholar Furthermore, the concomitant increase in risk of ICU admission and death, despite controlling for numerous risk factors, is concerning. Better powered studies should examine whether the increase in risk is disproportionately large in those younger than 50 years. A limitation of the study is that the VHA population has high rates of comorbidities and might not be reflective of the US population. However, our analysis reports an increase in risk between variants within the same population, rather than providing an estimation of absolute risk. Considering that vaccination still protects against adverse outcomes due to the delta variant,5Grannis SJ Interim estimates of COVID-19 vaccine effectiveness against COVID-19–associated emergency department or urgent care clinic encounters and hospitalizations among adults during SARS-CoV-2 B.1.617.2 (delta) variant predominance—nine states, June–August 2021.MMWR Morb Mortal Wkly Rep. 2021; 70: 1291-1293Crossref Google Scholar evidence of delta variant infection increasing the risk of hospitalisation and death among all age groups should inform vaccination policies. We declare no competing interests. This study used data created and maintained by the Veterans Health Administration, US Department of Veterans Affairs. These data are available to approved individuals upon request after fulfilling specified requirements. Download .pdf (.16 MB) Help with pdf files Supplementary appendix 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 studyThis 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. Full-Text PDF Open Access