August 28, 2021 1:02:03 pm
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 study has been published in The Lancet Infectious Diseases journal.
The risk of attending hospital for emergency care or being admitted to the hospital within 14 days of infection with the Delta variant was also one and a half times greater when compared to the Alpha variant (1.45-fold increase in risk).
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.
Dr Gavin Dabrera, one of the study’s lead authors and a consultant epidemiologist at the National Infection Service, Public Health England, said: “This study confirms previous findings that people infected with Delta are significantly more likely to require hospitalisation than those with Alpha, although most cases included in the analysis were unvaccinated. We 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 UK, it is vital that those who have not received two doses of vaccine do so as soon as possible. It is still important that if you have Covid-19 symptoms, stay home and get a PCR test as soon as possible.”
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 Alpha variant of Covid-19 that was first identified in Kent, UK.
In the latest study, researchers analysed 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 per cent) and 8,682 cases of the Delta variant (20 per cent). While the proportion of Delta cases in the study period overall was 20 per cent, it grew to account for around two-thirds of new Covid-19 cases in the week starting May 17, 2021 (65 per cent, 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 (2.2 per cent alpha cases, 764/34,656; 2.3 per cent delta cases, 196/8,682). 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 (2.26-fold increase in risk).
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 per cent (794/43,338) of patients had received both doses of the vaccine; 74 per cent of cases (32,078/43,338) were unvaccinated, and 24 per cent (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.
Dr Anne Presanis, who is another lead author of the study and is a senior statistician at the MRC Biostatistics Unit, University of Cambridge, said: “Our analysis highlights that in the absence of vaccination, any Delta outbreaks will impose a greater burden on healthcare than an Alpha epidemic. Getting fully vaccinated is crucial for reducing an individual’s risk of symptomatic infection with Delta in the first place, and, importantly, of reducing a Delta patient’s risk of severe illness and hospital admission.”