Covid-19 Delta variant doubles hospitalisation risk, study finds

People sit in a waiting room ahead of receiving a dose of the Covid-19 vaccine at a hospital in London, on Aug 1, 2021.
People sit in a waiting room ahead of receiving a dose of the Covid-19 vaccine at a hospital in London, on Aug 1, 2021.PHOTO: REUTERS

LONDON (BLOOMBERG) - People who contract the Delta variant of Covid-19 are more than twice as likely to be hospitalised as those infected with the Alpha strain, according to a UK study, raising the prospect of a greater burden on health services this winter.

The review of more than 43,000 Covid-19 cases in England, most of whom were unvaccinated or partially vaccinated, was published in The Lancet Infectious Diseases journal Friday (Aug 27), and highlighted the protection shots provide against hospitalisation from both variants.

The study assessed positive cases that occurred between March 29 and May 23, analysing samples of the virus using whole-genome sequencing to determine which variant a person was infected with.

Nearly three-quarters of the patients were unvaccinated, 24 per cent were partially vaccinated and 2 per cent had received both shots. Early studies of the Delta variant, which first appeared in India in December, found it was 50 per cent more transmissible than other strains. It quickly spread around the world to more than 130 countries, becoming the dominant variant in many.

As children return to school this fall and countries abandon lockdowns and isolation measures, the findings from Public Health England and the University of Cambridge suggest that health services could face an influx of patients.

"Our analysis highlights that in the absence of vaccination, any Delta outbreaks will impose a greater burden on healthcare than an Alpha epidemic," said Anne Presanis, one of the study's lead authors and a senior statistician at Cambridge. "Getting fully vaccinated is crucial for reducing an individual's risk of symptomatic infection with Delta."

Across the two-month study period, 80 per cent of the cases were Alpha and 20 per cent Delta, with Delta growing to account for two-thirds of the cases in the final week as it became the dominant strain in the UK, the authors said. While the researchers weren't given access to information on patients' pre-existing health conditions, they factored in age, gender, ethnicity and estimated level of socioeconomic deprivation to account for those more likely to be hospitalised from Covid-19.

A study in Scotland published in June also found the Delta variant doubled the risk of hospitalisation compared with Alpha, which first was identified in Kent, England.

In the US, Department of Health and Human Services data show younger people are being admitted to the hospital at the highest rates on record, even though significantly fewer people are testing positive than did in the December and January peak. For the oldest Americans, hospitalisation rates per 100,000 are lower than previous peaks, probably due to very high vaccination rates. The data don't cover the first wave of the pandemic.