Scientists from the Centers for Disease Control and Prevention on Friday took aim at the question of whether the Delta variant of the coronavirus causes more severe disease, finding no significant differences in the course of hospitalized patients’ illnesses during the Delta wave compared to earlier in the pandemic.

But larger and more detailed studies from a number of other countries have found that people with Delta infections were considerably more likely to be hospitalized in the first place — a trend that the C.D.C. study was unable to address because of limitations in its data. The C.D.C. study also said that the proportion of older hospitalized patients needing intensive care or dying had shown some signs of increasing during the Delta wave…

Studies in England, Scotland, Canada and Singapore suggested that the Delta variant was associated with more severe illness, a finding that scientists have said raises the risk that outbreaks of the variant in unvaccinated areas may put a bigger burden on health systems. Unlike the C.D.C. study, those studies drew on genomic sequencing, allowing researchers to distinguish infections with the Delta variant and to track patients from before they enter a hospital.