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Delta variant doubles risk of COVID-19 hospitalization for unvaccinated, study suggests

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A new study out of the U.K. suggests the Delta variant doubles the risk of COVID-19 hospitalization for unvaccinated and partially vaccinated people compared to the Alpha variant.

The study, published in , examined more than 40,000 cases of COVID-19 in England between March 29 and May 23 2021. Researchers say it鈥檚 the first to report hospitalization risk for Delta versus Alpha variants based on cases confirmed by whole-genome sequencing.

The study suggests that not only do people infected with the Delta variant have approximately double the risk of hospitalization compared to the Alpha variant, but that the risk of needing emergency care or hospital admittance within 14 days of infection with the Delta variant was also one-and-a-half times greater compared to the Alpha variant.

The Delta variant was first reported in India in December 2020 and early studies found it to be up to 50 per cent more transmissible than the variant of COVID-19 that had previously gained global dominance, known as the Alpha variant, first identified in the U.K.

鈥淭his study confirms previous findings that people infected with Delta are significantly more likely to require hospitalization than those with Alpha, although most cases included in the analysis were unvaccinated,鈥 said lead study author and epidemiologist Dr. Gavin Dabrera in a press release.

鈥淲e already know that vaccination offers excellent protection against Delta and as this variant accounts for over 98 per cent of COVID-19 cases in the U.K., it is vital that those who have not received two doses of vaccine do so as soon as possible,鈥 Dabrera continued.

Researchers analyzed healthcare data from 43,338 positive COVID-19 cases during the study time period, including vaccination status, emergency care attendance, hospital admission and other demographic characteristics.

In all cases included in the study samples of the virus taken from patients underwent whole genome sequencing to confirm which variant they had contracted.

Around one in 50 patients in the study was admitted to hospital within 14 days of their first COVID-19 test. After factoring in variables that attribute to a patient鈥檚 susceptibility to severe COVID-19 outcomes like age, ethnicity and vaccination status, the researchers determined the risk of being admitted to hospital was more than doubled with the Delta variant compared with the Alpha.

The study notes multiple studies have shown that full vaccination prevents both symptomatic infection and hospitalization, for both Alpha and Delta variants.

鈥淚ndeed in this study only 1.8 per cent of COVID-19 cases (with either variant) had received both doses of the vaccine; 74 per cent of cases were unvaccinated and 24 per cent were partially vaccinated,鈥 the study says.

The authors note it鈥檚 not possible to draw statistically significant conclusions about how the hospitalization risk differs between vaccinated persons who later develop Alpha and Delta infections.

鈥淭he results from this study therefore primarily tell us about the risk of hospital admissions for those who are unvaccinated or partially vaccinated.鈥

A WARNING FOR CANADA

President and Medical Director of the Vancouver, B.C., Infectious Diseases Centre (VIDC) Dr. Brian Conway said the study should be a 鈥渨arning鈥 to Canada come the fall, as the delta variant continues to push COVID-19 cases higher.

鈥淚t鈥檚 a very large population-based study, and after adjusting for various medical comorbidities that are associated with an increased risk of hospitalization, [it found] that those who are infected with a Delta variant are twice as likely to require hospitalization,鈥 Conway said to CTV National News Chief Medical Correspondent Avis Favaro.

鈥淪o the issue is raised, but the solution is also presented to us,鈥 he continued. 鈥淭hose who had received a double dose of vaccine at least 14 days before being diagnosed with COVID-19 only accounted for 3.9 per cent of those who required hospitalization.鈥

Conway said a major takeaway from the study would be to 鈥渧accinate more鈥 in light of the effect the delta variant could have on the public health system in Canada.

鈥淎 very small minority of those who required hospitalization, less than five per cent, had been fully vaccinated,鈥 he said. 鈥淪o I think that it鈥檚 a really good call to arms for Canada 鈥 lets get back to the vaccination rates that we were seeing in late June鈥ight now we鈥檙e barely vaccinating 100,000 people per day and we know we can do more.鈥

The pace of vaccinations in Canada has slowed, from 600,000 a day early in the rollout to less than , with millions of Canadians unvaccinated or .

In Alberta, unvaccinated people are causing a surge of COVID-19 cases, with 1,168 cases reported Friday and 98 per cent of patients in the ICU are unvaccinated.

鈥淭he majority of infections we are seeing across Canada are in the unvaccinated,鈥 said Chief of Family Medicine at Markham, Ont., Stouffville Hospital Dr. Allan Grill to CTV National News. 鈥淲hen you get COVID-19, we know you can end up in a hospital, in the ICU, there are very bad outcomes with this disease.鈥

鈥淚 think this paper really suggests to us what would happen if we choose not to do more鈥ssentially delta accounts for virtually 100 per cent of the new cases that are diagnosed on a daily basis in Canada,鈥 Conway continued.

Conway鈥檚 concern for strain on the healthcare system under a steady onslaught of Delta variant COVID-19 cases are echoed by study lead author and senior statistician at the University of Cambridge Dr. Anne Presanis.

鈥淥ur analysis highlights that in the absence of vaccination, any Delta outbreaks will impose a greater burden on health care than an Alpha epidemic,鈥 Presanis said in the release. 鈥淕etting fully vaccinated is crucial for reducing an individual鈥檚 risk of symptomatic infection with Delta in the first place, and more importantly, of reducing a Delta patient鈥檚 risk of severe illness and hospital admission.鈥 

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