Researchers revealed on Saturday in The Lancet that the Delta version of the virus that causes Covid-19 increases the risk of hospitalisation compared to the Alpha variant it has superseded as the prevalent strain globally.
Only 1.8 percent of the more than 43,000 Covid cases assessed in comparing the two variants were in patients who had been fully vaccinated.
Three-quarters were completely unvaccinated, and 24 percent had only received one jab of a two-dose vaccine.
“The results from this study therefore primarily tell us about the risk of hospital admission for those who are unvaccinated or partially vaccinated,” said co-lead author Anne Presanis, a Senior Statistician at the University of Cambridge’s MRC Biostatistics Unit.
Researchers analysed healthcare data from 43,338 COVID-19 cases in England from March 29 to May 23 of this year, including vaccination status, emergency care, hospital admission and other patient information.
All virus samples underwent whole genome sequencing, the surest way to confirm which variant had caused the infection.
Just under 80 percent of the cases were identified as the Alpha variant, and the rest were Delta.
Around one in 50 patients were admitted to hospital within 14 days of their first positive Covid-19 test.
After accounting for factors that are known to affect susceptibility to severe illness — including age, ethnicity, and vaccination status — the researchers found the risk of being admitted to hospital was more than doubled with the Delta variant.