People infected with the delta variant are more than twice as likely to be hospitalized for Covid-19 than those with the original alpha variant, according to a study published in The Lancet Infectious Diseases journal on Friday, which backs up previous research indicating the hyper-infectious strain may cause more severe disease.
Researchers from Public Health England (PHE) and Cambridge University looked at healthcare data from 43,338 positive coronavirus cases in England between March 29 and May 23 that they confirmed were caused by either the alpha or delta variant through whole-genome sequencing, the most accurate way to determine a virus variant.
Alpha, a mutation that originated in the U.K. and spreads faster than previous strains, made up a vast majority (80%) of the analyzed cases as it was the dominant variant when the study began, but had by the end been taken over by delta, which data indicate is between 40% and 60% more transmissible than the U.K. strain.
Of the 34,656 alpha cases, 764 (or 2.2%) ended up hospitalized within 14 days of testing positive for the virus, while 196 of the 8,682 delta cases (2.3%) ended up admitted to a hospital during that period.
After adjusting for factors like age, ethnicity and vaccination status “that are known to affect susceptibility to severe illness from Covid-19,” the researchers found the risk of being admitted to hospital increased 2.26-fold with the delta variant.
The peer-reviewed study highlighted that only 1.8% of the cases of either variant were among people who had received both doses of the vaccine, meaning its results “primarily tell us about the risk of hospital admission for those who are unvaccinated or partially vaccinated.”
“Further research is needed” to see how hospitalization risks compare between fully vaccinated individuals infected with the delta variant compared to the alpha variant, the researchers said, noting a previous study estimated low hospitalization risks for vaccinated individuals with either variant.
“Our analysis highlights that in the absence of vaccination, any delta outbreaks will impose a greater burden on healthcare than an alpha epidemic,” Dr. Anne Presanis, a senior statistician at the Medical Reserve Corps and a lead author of the study, said in a statement. “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.”
The findings of this study line up with previous research indicating the delta variant is more likely to cause hospitalization. A Scottish study published in June also found delta, first identified in India, carried about double the risk of hospitalization compared with alpha. Studies from Canada and Singapore have similarly suggested that delta leads to more severe illness, with the research from Singapore finding delta-infected coronavirus patients were more likely to require Oxygen. The Centers for Disease Control and Prevention (CDC) cited these three studies in an internal report whose concerning warnings about the delta variant were made public by news organizations in late July. The agency acknowledges on its website that “some data suggest the delta variant might cause more severe illness than previous variants in unvaccinated people.”
The delta variant has been driving a massive surge in hospitalizations across the U.S. which has seen more than 100,000 hospitalized with the virus for the first time since January. It has been predominantly impacting unvaccinated Americans and is currently overwhelming the healthcare systems of multiple states with inoculation rates below the national average. An average of about 1,200 Americans are dying each day from Covid-19, according to data from The New York Times.