Among patients with COVID-19, those infected with the Delta variant were found to be at increased risk for hospitalization and emergency department (ED) admission compared with those infected with the Alpha variant, according to study results published in The Lancet Infectious Diseases.

Between March and May 2021, researchers in England conducted a cohort study to compare the risk for hospitalization and ED admission among patients with COVID-19 infected with the Alpha variant vs those infected with the Delta variant. A total of 43,338 patients with COVID-19 infected with either the Alpha (n=34,656) or Delta (n=8682) variants were included in the study. The researchers used whole-genome sequencing to identify whether patients with COVID-19 were infected with the Alpha or Delta variant. Patients were divided into subgroups according to SARS-CoV-2 variant type and vaccination status. The researchers used stratified Cox regression to adjust for age, sex, ethnicity, socioeconomic status, recent international travel, residence, date of specimen collection, and vaccination status.

Among patients in the cohort, the median age was 31 (interquartile range [IQR], 17-43) years, and most (74%) were unvaccinated. Of note, patients infected with the Delta variant were younger (median age, 29 years; IQR, 15-41) compared with those with the Alpha variant (median age, 31 years; IQR, 17-43). Increased risk for hospital and ED admission within 14 days of confirmed infection was noted among patients with the Delta variant who were unvaccinated compared with those with the Alpha variant (adjusted hazard ratio, 1.43; 95% CI, 1.04-1.97; P =.82). No significant differences in the estimated risk for hospitalization or ED admission were noted in vaccinated patients infected with the Alpha vs Delta variants. Among patients with COVID-19 who had received only the first vaccine dose, the relative risk precision was too low to determine whether there was similar or increased risk for hospitalization in those with the Delta vs Alpha variants.

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Excluding subgroup analysis by symptom status, sensitivity analyses showed significantly increased risks for both hospitalization and ED admission among patients with the Delta variant compared with those with the Alpha variant.

The study was limited by its potential inclusion of inaccurate data on hospital admissions due to monthly reporting delays and the lack of information on study patients’ comorbidities. In addition, patients with a recent history of international travel and those who self-identified as an ethnic minority were overrepresented in the Delta variant group.

The researchers noted that because a large proportion of patients in the cohort were analyzed only within the 28-day follow-up period, “further work is needed to measure the risk of mortality [associated with] the Delta variant.” Results of this study suggest that “outbreaks of the delta variant in unvaccinated populations might lead to a greater burden on healthcare services compared with the Alpha variant,” the researchers concluded.


Twohig AK, 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. Published online August 27, 2021. doi:10.1016/S1473-3099(21)00475-8

This article originally appeared on Infectious Disease Advisor