Delta variant patients have double the risk of hospitalisation

A study published today in The Lancet of more than 40,000 positive Covid-19 cases in the UK has suggested that people infected with the SARS-CoV-2 Delta variant have approximately double the risk of hospitalisation — compared to those infected with the Alpha variant.

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 more significant burden on healthcare services than the Alpha variant. Most patients were unvaccinated (32078 [74·0%] across both groups) while 24% were partially vaccinated.

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. The Delta variant is suspected to be associated with a more severe disease than the previously dominant Alpha (B.1.1.7) variant. The study aimed to characterise the severity of the Delta variant compared with the Alpha variant by determining the relative risk of hospital attendance outcomes.

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 healthcare 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 was 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 (8,682 with the Delta variant, 34,656 with the Alpha variant; median age 31 years [IQR 17–43]) were included in the analysis.

196 (2·3%) patients with the Delta variant versus 764 (2·2%) patients with the Alpha variant were admitted to the 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]

Dr Gavin Dabrera, one of the study’s authors and a Consultant Epidemiologist at the National Infection Service, Public Health England, said: “This study confirms previous findings that people infected with Delta are significantly more likely to require hospitalisation than those with Alpha, although most cases included in the analysis were unvaccinated.

We already know that vaccination offers excellent protection against Delta. As this variant accounts for over 98% of Covid-19 cases in the UK, it is vital that those who have not received two doses of vaccine do so as soon as possible. It is still important that if you have Covid-19 symptoms, stay home and get a PCR test as soon as possible.”

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