Europe 1 with AFP 9:27 am, August 28, 2021

People infected with the Delta variant are twice as likely to be hospitalized for Covid-19 than those infected with the Alpha variant.

This is the conclusion of a British study published on Saturday.

So far, only the high transmissibility of this variant had been demonstrated, but data were lacking on its dangerousness.

People infected with the Delta variant are twice as likely to be hospitalized for Covid-19 than those infected with the Alpha variant, concludes a British study published on Saturday.

"Our analysis shows that if we did not have the vaccination, an epidemic due to the Delta variant would place a greater burden on the health system than if it were caused by the Alpha variant", underlined Anne Presanis, co-author of the study.

A study of 43,000 cases

It is already known that the Delta variant, first identified in India, is around 40% to 60% more transmissible than the Alpha variant, which had emerged in the UK at the end of 2020. But little information is yet available on its severity, even though preliminary data in Scotland and Singapore already suggested an increased risk of hospitalization and severe forms of Covid with this variant.


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The authors of the study published in the journal The Lancet Infectious Diseases analyzed data from more than 43,000 Covid cases recorded in England between March 29 and May 23, when the Delta variant began to spread across the Channel. .

The proportion of cases linked to the Alpha variant (confirmed by sequencing) was 80% on average over the entire period (99.8% in the first week, declining to 34.8% in the last), while 20% were due to the Delta variant.

A risk multiplied by 2.26

Three-quarters of them (74%) were not vaccinated and a quarter (24%) had only received a single dose, with fully vaccinated people accounting for only 1.8% of infections.

2.3% of Delta positive cases were hospitalized within two weeks of testing positive, compared to 2.2% of Alpha variant cases.

But by restating the data to take into account factors known to vary the risk of severe form of Covid (age, ethnic group, vaccination status), the researchers calculate that the risk of being admitted to the hospital is multiplied by 2, 26 with the Delta variant compared to the Alpha variant.

The patients affected by the Delta variant were notably younger, with a median age of 29 years, against 31 years for the Alpha variant.

Getting vaccinated is "vital"

Given the low proportion of people vaccinated in the population studied, "the results of this study tell us above all about the risk of admission to hospital for those who are not vaccinated or partially vaccinated", underlines Anne Presanis, statistician at Cambridge University.

Several studies have shown that the vaccines retain a very high efficacy against severe forms of Covid linked to the Delta variant, provided they have a complete vaccination. Their effect is limited after a single dose. "While this variant now accounts for more than 98% of Covid-19 cases in the UK, it is vital that those who have not received two doses do so as quickly as possible," said Gavin Dabrera, co-author study and epidemiologist at Public Health England.