SARS-CoV-2 Delta Variant is More Virulent Than Original Strain, Reveals a New Study

A new study evaluated the relative virulence of novel SARS-CoV-2 variants and found that the delta variant is more virulent than other variants. This evaluation paves way for control of the COVID-19 pandemic.

Among the SARS-CoV-2 variants of concern (VOCs), the Delta variant is more virulent than the native strain of the virus by increasing people's risk of hospitalization, admission to the intensive care unit (ICU), and death due to COVID-19.

This finding is revealed by a large study from Ontario, which is published in CMAJ (Canadian Medical Association Journal).

Coronavirus
Coronaviruses infect animals, humans, and birds. Human coronaviruses, such as SARS, MERS, and 2019-nCoV cause respiratory distress and even death. The S protein is the infectious agent of the virus.

‘The emergence of novel SARS-CoV-2 variants of concern (VOCs) has slowed progress against the COVID-19 pandemic.’

The study included 212 326 cases of COVID-19 reported between February 7 and June 26, 2021, in Ontario, Canada's largest province with a population of almost 14.8 million.

COVID-19 variants of concern include those with the N501Y mutation such as Alpha, Beta, and Gamma as well as Delta, which have replaced the original SARS-CoV-2 strain.

Of the total cases, 22.4% were non-VOC, 76.7% were infections with N501Y mutations, and 2.8% were probable Delta. By April 2021, the Delta variant was present in Ontario and was the dominant strain by July 2021.

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People infected with VOCs were significantly younger and less likely to have comorbidities than those with non-VOC infections.

The risks of hospitalization were 52% higher, admission to ICU was 89% higher and death was 51% higher in Alpha, Beta, and Gamma infections. Whereas in Delta infections, risks were 108%, 235% and 133% higher, respectively.

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Even after adjusting for age, sex, comorbidities, and other factors, the increased risk of adverse outcomes persisted.

Researchers also looked at the effect of vaccination, which blunted the severity of VOCs by reducing the risk of severe disease and death in partially and fully vaccinated people.

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The vaccination effect reported in this study represent a substantial degree of protection against death conferred by vaccines (about 80%–90%), even when they fail to prevent infection.

Such direct protective effects may help reduce the health impacts of ongoing SARS-CoV-2 transmission in Ontario, even if herd immunity proves elusive, given the high reproduction numbers of VOCs.

This new study findings add to studies from England, Scotland, and Singapore indicating the Delta variant increases the risk of emergency department use, hospitalization, and severe outcomes.

Effective measures such as boosting SARS-CoV-2 vaccination rates in Canada by extending vaccine mandates; prioritizing the approval of safe vaccines for children; working with other countries to ensure vaccine delivery globally; and continuing to use established public health tools can identify, track and control COVID-19 outbreaks.

Source-Medindia