Unvaccinated hospitalization and death rates are roughly 2x higher with delta. https://www.thelancet.com/journals/lancet/article/PIIS0140-6736(21)01358-1/fullt

Unvaccinated hospitalization and death rates are roughly 2x higher with delta. https://www.thelancet.com/journals/lancet/article/PIIS0140-6736(21)01358-1/fulltext https://www.thelancet.com/journals/lancet/article/PIIS0140-6... Transmissibility and virulence tend to be linked via in-host replication rate (viral load). It isn't quite that simple since if the virus can better evade in-host immune responses then higher viral loads could be better tolerated by the host, but generally transmissibility and virulence are expected to move together. It isn't clear that D614G or B.1.1.7/Alpha involved enhancements in virulence, but delta's advantage in transmission over Alpha does seem to come from increased viral loads, which causes more severe symptoms.