Two early studies suggest a reduced risk of Covid-19 hospitalization when infected with Omicron compared to Delta
Both studies include preliminary data and have not yet been published in a peer-reviewed journal.
The study out of Scotland included data on 23,840 Omicron cases and 126,511 Delta cases, from November 1 to December 19. The researchers — from the University of Edinburgh, University of Strathclyde and Public Health Scotland — took a close look at the health outcomes among those Omicron infections compared with Delta infections. There were 15 hospital admissions among those with Omicron infections and 856 hospital admissions among Delta.
“The study is rigorous but it is early (thus might change a bit with more data and more studies will report in the weeks ahead). It should be noted that some South African scientists have been saying Omicron was milder for some time,” Naismith said. “Although two thirds reduction is significant, Omicron can cause severe illness in the doubly vaccinated. Thus, if Omicron continues to double every few days, it could generate many more hospitalisations than Delta from the double vaccinated population.”
The researchers found that the proportion of Omicron cases that were likely reinfections in people who have had Covid-19 before was more than 10 times that of Delta. The data also showed that having received a third dose of vaccine, or booster shot, was associated with a 57% reduction in the risk of symptomatic Omicron infection when compared with being at least 25 weeks out from completing a second dose.
“These early national data suggest that Omicron is associated with a two-thirds reduction in the risk of COVID-19 hospitalisation when compared to Delta. Whilst offering the greatest protection against Delta, the third/booster dose of vaccination offers substantial additional protection against the risk of symptomatic COVID-19 for Omicron,” the researchers wrote in the paper.
The other paper involved data on 161,328 Covid-19 cases reported nationally in South Africa between October 1 and December 6. The researchers — from the National Institute for Communicable Diseases, University of the Witwatersrand and the University of Cape Town — found that among people with Omicron infection, 2.5% were admitted to the hospital during that time compared with 12.8% of people with Delta infection.
The researchers wrote in their paper, “These are early data and findings may change as the epidemic progresses.”
