Delta Variant Doubles Risk Of Hospitalisation When Compared
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People infected with the Delta variant of the novel coronavirus have approximately double the risk of hospitalisation compared to those infected with the Alpha variant, a study of more than 40,000 cases from England between March 29 and May 23 this year has confirmed.

The new study is the first to compare the number of people who were hospitalised after being infected with the Delta and Alpha variants. The study, however, only took into account cases confirmed by whole-genome sequencing, which is the most accurate way to determine the virus’s variant.

In the latest study, researchers analyzed healthcare data from 43,338 positive Covid-19 cases in England, including information on 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 had caused the infection.

During the study period, there were 34,656 cases of the Alpha variant (80 percent) and 8,682 cases of the Delta variant (20 percent). While the proportion of Delta cases in the study period overall was 20 percent, it grew to account for around two-thirds of new Covid-19 cases in the week starting May 17, 2021 (65 percent, 3,973/6,090), indicating it had overtaken Alpha to become the dominant variant in England.

Around one in 50 patients were admitted to the hospital within 14 days of their first positive Covid-19 test. After accounting for factors that are known to affect susceptibility to severe illness from Covid-19, including age, ethnicity, and vaccination status, the researchers found the risk of being admitted to hospital was more than double with the Delta variant when compared to the Alpha variant.

Multiple studies have shown that full vaccination prevents both symptomatic infection and hospitalisation, for both Alpha and Delta variants. However, in this study, only 1.8 percent (794/43,338) of patients had received both doses of the vaccine; 74 percent of cases (32,078/43,338) were unvaccinated, and 24 percent (10,466/43,338) were partially vaccinated.

The authors, therefore, stated that it was not possible to draw statistically significant conclusions about how the hospitalisation risk differs between vaccinated persons who later develop Alpha and Delta infections. The results from this study, therefore, primarily inform about the risk of hospital admission for those who are unvaccinated or partially vaccinated.