Delta variant twice as likely to put patients in hospital

THE delta variant of Covid-19 doubles patients’ risk of hospitalisation compared with the alpha variant, a study of 40,000 cases in England has found.

The study, published in The Lancet, also found the risk of being admitted to hospital within 14 days of infection with the delta variant was one and a half times greater than alpha.

First reported in India in December 2020, the delta variant spread to account for the majority of cases in England by May 2021.

Previous studies have also found it to be around 50 per cent more transmissible than the alpha variant, which was first seen in Kent in September 2020.

Researchers at Public Health England and the University of Cambridge analysed more than 40,000 confirmed Covid-19 cases between March 29 and May 23, 2021.

Patients’ vaccination status, emergency care attendance, hospital admission, and other demographic characteristics were taken into account.

All samples underwent genome sequencing to determine which variant had infected the patients, making it the first study of its kind to report the risk of hospitalisation from different variants using this method.

Delta cases accounted for 20 per cent of the samples during the study, but had grown to represent more than three fifths of the cases by May 17.

Researchers found 2.2 per cent of alpha cases (764/34,656) and 2.3 per cent of delta cases, (196/8,682) were hospitalised within two weeks of their first positive test. But when accounting for factors such as age, ethnicity, and vaccination status – which are known to impact the severity of the virus – they found the risk of hospitalisation from delta more than doubled compared with alpha (a 2.26-fold increase).

The authors highlighted the role of vaccinations in controlling the virus, saying that around 2 per cent of cases were doubled vaccinated but three quarters were unvaccinated.

Dr Anne Presanis, one of the study’s lead authors and senior statistician at the MRC Biostatistics Unit, University of Cambridge, said: “Our analysis highlights that in the absence of vaccination, delta outbreaks will impose a greater burden on healthcare than an alpha epidemic.”