According to a large-scale Canadian study, the Delta variant of the coronavirus is 133% more deadly than the original one. Although vaccines remain effective in preventing severe forms of COVID-19 the emergence of the different variants has considerably delayed the end of the pandemic,
The Delta variant, virtually non-existent in January, now accounts for most current infections. Several studies have already demonstrated the higher infectivity and virulence of the Delta variant. It is also more likely to escape the vaccine: the efficacy of the Moderna and Pfizer vaccines dropped significantly with this variant, compared to the original virus.
An extensive new study conducted in Canada confirmed the extreme virulence of the delta variant. The study, conducted between February and June 2021 on 212,326 people, compared the risks of hospitalization, emergency room admission, and death associated with the different variants that were then in circulation (Alpha, Beta, Gamma, and Delta) with the original virus. The result: the risk of hospitalization, emergency admission, and death was 108%, 235%, and 133% higher for the Delta variant, respectively. In other words, where one in 100 people died from the original SARS-CoV-2, 2.33 people died when infected with the Delta variant.
Virulence is also higher in Alpha, Beta, and Gamma variants, but to a lesser extent (52% for risk of hospitalization, 89% for risk of emergency admission, and 51% for risk of death). “Even after adjusting for age, sex and comorbidities, the risk remained the same,” the researchers stress. “The emergence of new variants of SARS-CoV-2 has slowed progress against the pandemic in three different ways,” said David Fisman, co-author of the paper which is published in the Canadian Medical Association Journal (CMAJ), “namely, by increasing transmissibility and the rate of viral replication, increasing immune evasion, and increasing the virulence of the infection.
The good news is that the vaccines remain highly effective against severe forms of the disease. “Vaccines provide a significant degree of protection against death (about 80-90%), even if they fail to prevent infection,” the authors say. This helps limit virus transmission even if herd immunity has proven difficult to achieve.
“We are facing a very different epidemic than in 2020,” confirms Kirsten Patrick, editor-in-chief of CMAJ, in an editorial accompanying the article. The virus has gotten smarter and more dangerous, which means we need to get smarter too. Governments must ensure the safety of their citizens by adopting policies that judiciously combine all the measures that have proven to be effective. He calls for expanded vaccination, a ban on anti-vaccine rallies near schools and health facilities, approval of safe vaccines for children, effective international cooperation to ensure the global supply of vaccines, or continued work on mapping, surveillance, and epidemic control.
Unfortunately, the end of the pandemic is not yet in sight, and Covid is likely to become even more endemic. “We should expect new variants to appear, given its intense spread around the world in recent months.
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