COVID-19 VOCs – Especially Delta Variant – More Virulent Than Original Strain

A large Ontario study confirms that SARS-CoV-2 variants of care (VOCs), especially the Delta variant, are more virulent than the native strain of the virus, increasing the risk of hospitalization, intensive care (ICU) admission. increases for people. and death from COVID-19. The research is published in the CMAJ (Canadian Medical Association Journal).

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 nearly 14.8 million. Variants of concern include those with the N501Y mutation, such as Alpha, Beta, and Gamma, as well as Delta, which 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 probably Delta.

In April 2021, the Delta variety was present in Ontario and was the dominant species in July 2021.

“The emergence of new SARS-CoV-2 VOCs has slowed progress against the pandemic in three different ways, namely by increasing the transmissibility and reproduction rate of the virus, by increasing immune escape and decreasing vaccine effectiveness, and by the virulence of SARS-CoV-2 infection,” write co-authors Drs David Fisman and Ashley Tuite, Dalla Lana School of Public Health, University of Toronto, Toronto, Ontario.

Some findings:

People infected with VOCs were significantly younger and less likely to have co-morbidities than people with non-VOC infections Infections with VOCs were more common in the Greater Toronto and Hamilton Area, Ontario’s largest metropolis Delta variants were significantly less common in Ottawa , Ontario’s second largest metropolitan area. With Alpha, Beta, and Gamma VOC infections, the risk of hospitalization was 52% higher, ICU admission 89% higher, and death 51% higher; with Delta infections, the risks were 108%, 235% and 133% higher, respectively

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

The researchers also looked at the effect of vaccination, which attenuated the severity of VOCs by reducing the risk of serious illness and death in partially and fully vaccinated people.

“The effects reported here represent a substantial degree of protection against death conferred by vaccines (approximately 80% – 90%), even if they fail to prevent infection. Such direct protective effects could help mitigate the health effects of the continued transmission of SARS-CoV-2 in Ontario, even if herd immunity proves elusive, given the high reproductive rate of VOCs,” the authors write.

The study results complement studies from England, Scotland and Singapore that indicate that the Delta variant increases the risk of emergency room use, hospitalization and serious consequences.

“The increasing virulence of SARS-CoV-2 VOCs will lead to a significantly larger and deadlier pandemic than would have occurred without the emergence of VOCs,” the authors write.

In a related editorial, Dr. Kirsten Patrick, Interim Editor-in-Chief, CMAJ, urges Canadian leaders to use all available tools to control the spread of SARS-CoV-2 as a second COVID-19 pandemic winter approaches.

“Canada is facing a different pandemic than the one it faced in early 2020. The virus has gotten smarter and more dangerous, which means we need to be smarter too. Canada’s governments can protect people by enacting policies that judiciously combine all measures that have been shown to be effective,” writes Dr. patrick.

Effective measures include increasing SARS-CoV-2 vaccination rates in Canada by extending vaccine mandates and passports and banning anti-vaccination gatherings near health and education facilities; prioritize the approval of safe vaccines for children; collaborating with other countries to ensure the delivery of vaccines worldwide; and continuing to use established public health tools to identify, detect and control outbreaks.

“We must collectively learn from past mistakes and ensure that we use all available resources to avoid future lockdowns and prevent further destruction of our healthcare infrastructure,” she concludes.

Reference: “Evaluating the Relative Virulence of Novel SARS-CoV-2 Variants: A Retrospective Cohort Study in Ontario, Canada” by David N. Fisman and Ashleigh R. Tuite, Oct. 4, 2021, Canadian Medical Association Journal.
DOI: 10.1503/cmaj.211248