Delta strain doubles hospitalisation risk

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The Delta COVID variant was found to be more transmissible and doubles the risk of hospitalisation.
Camera IconThe Delta COVID variant was found to be more transmissible and doubles the risk of hospitalisation. Credit: EPA

The Delta coronavirus variant doubles the risk of hospitalisation compared with the previously dominant variant in Britain, but vaccination offers significant protection, a Scottish study has found.

However the study said early evidence suggested the protection from vaccines against the Delta variant, first identified in India, might be lower than the effectiveness against the Alpha variant, first identified in southeast England.

British Prime Minister Boris Johnson is expected to delay the ending of COVID-19 restrictions in England on Monday, following a rapid rise in cases of the Delta variant, which is also more transmissible than the Alpha variant.

The study, published in a research letter in the Lancet, looked at 19,543 community cases and 377 hospitalisations among 5.4 million people in Scotland.

Among those studied, 7723 cases including 1234 hospitalisations were found to have the Delta variant.

Professor of Public Health Epidemiology Chris Robertson said that adjusting for age and comorbidities, the Delta variant roughly doubled the risk of hospitalisation, but vaccines still reduced that risk.

"If you test positive, then two doses of the vaccine or one dose for 28 days roughly reduces your risk of being admitted to hospital by 70 per cent," the University of Strathclyde professor told reporters.

Two weeks after the second dose, Pfizer's vaccine was found to have 79 per cent protection against infection from the Delta variant, compared to 92 per cent against the Alpha variant.

For AstraZeneca's vaccine, there was 60 per cent protection against Delta compared with 73 per cent for Alpha.

The researchers cautioned against using the data to compare the vaccines against each other due to differences in the cohorts which received each type of shot, and differences in how quickly immunity is developed with each shot.

They said two doses of vaccine provide much better protection than one dose against the Delta variant, and a delay to easing lockdown in England would help more people get second doses and allow time for their immune responses to build up.

Aziz Sheikh, Director of the Usher Institute at the University of Edinburgh, said any delay to ending lockdown would aid the pandemic battle.

"I think any sort of increase in the window of opportunity before lockdown measures are completely brought to an end will be helpful," he said.

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