The Delta variant of the coronavirus, also prevalent in Italy, with its symptoms doubles the risk of hospitalization for covid compared to the Alpha variant. This is confirmed by a new British study, the largest to date, which analyzed more than 40,000 cases confirmed by sequencing in England between 29 March and 23 May 2021. The probability of needing emergency visits or hospitalization was even 1.5 times greater for people infected with Delta than for those affected by Alpha.
The results of the work suggest that epidemics sustained by this variant, now prevalent in Europe, “may lead to a greater burden on health services” than those caused by the Alpha mutant now ousted from its dominant position, “particularly in unvaccinated people. and in other vulnerable populations “, is the alarm raised by the authors of the study. The researchers especially caution about the increased risk of hospitalization among unvaccinated or partially vaccinated people, as these made up the majority of cases examined in the study.
The Delta variant was first reported in India in December 2020, and early studies had quickly found that it is up to 50% more transmissible than the Alpha variant, first identified in Kent, UK. Now this work confirms a risk of hospitalization roughly double for those infected with Delta compared to those infected with Alfa. The risk of going to the hospital for emergency care or being hospitalized within 14 days of infection is also one and a half times greater than with the Alpha variant (1.45 times).
This new study is based on cases “confirmed by whole genome sequencing, which is the most accurate way to determine the viral variant”. His conclusions are in line with previous findings, for example from a preliminary study conducted in Scotland that had already reported a doubling of the risk of hospitalization and supported the suspicion that Delta was associated with a more serious disease.
“Most of the cases included in the analysis were unvaccinated – specifies Gavi Dabrera, of the National Infection Service, Public Health England (Phe), one of the lead authors of the study – We already know that vaccination offers excellent protection against Delta and as this variant accounts for over 98% of Covid cases in the UK, it is imperative that those who have not received two doses of the vaccine do so as soon as possible. It is still important in the event of symptoms to stay home and swab as soon as possible. possible”.
During the study period, there were a total of 34,656 cases of the Alpha variant (80%) and 8,682 cases of the Delta (20%). But the proportion of Delta cases has been growing to account for about two-thirds of new cases in the week starting May 17, 2021 (65%, 3,973 / 6,090), and overtaking Alfa in England. About one in 50 patients was hospitalized within 14 days of the first positive test (2.2% of Alpha cases, 2.3% of Deltas). And, taking into account all the factors known to influence susceptibility to severe Covid, they calculated a more than doubled risk of hospitalization with the Delta variant (2.26 times higher).
In this study, only 1.8% of cases (with both variants) had received both doses of the vaccine; 74% were unvaccinated and 24% had only one dose. The authors note that it is therefore not possible to draw statistically significant conclusions about how the risk of hospitalization differs among vaccinated people who subsequently develop Alpha and Delta infections. The results of this study therefore speak mainly to the risk of hospitalization for those who are unvaccinated or partially vaccinated.
“Our analysis shows that, in the absence of vaccination, any Delta epidemic will place a greater burden on health care than an Alpha epidemic,” concludes Anne Presanis, senior statistician at Cambridge University and one of the study’s lead authors. , which was led by researchers from Public Health England and the University of Cambridge and funded by UK Research and Innovation, Medical Research Council, the UK Government’s Department of Health and Social Care and National Institute for Health Research.