Two new studies from Britain and Scotland support early data from South Africa that while the Omicron variant of COVID appears to be more transmissible, it may cause less severe illness than the Delta variant.
The first study from the Imperial College London COVID response team evaluated all confirmed PCR-tested cases of Omicron and Delta in the first half of December — specifically how many cases of each variant were hospitalized. It found that of 56,000 Omicron cases and 269,000 Delta cases, those with Omicron were about 20 percent less likely to seek hospital care at all and 40 percent less likely to be hospitalized overnight or longer.
In the second study from University of Edinburgh scientists and other experts reported Omicron patients were two-thirds less likely to be hospitalized than Delta patients.
However, the study acknowledged that almost 24,000 Omicron cases evaluated in Scotland were mostly among people aged 20 to 39, who are much less likely to suffer from severe COVID cases.
While the variant may be less likely to hospitalize a patient, several scientists told The Associated Press hospital systems could still face significant pressure as the cases could pile up faster because the Omicron variant is proving to be more transmissible and vaccine-resistant than previous variants.
"Cautious optimism is perhaps the best way to look at this," Manuel Ascano Jr., a biochemist at Vanderbilt University told the AP.
"This national investigation is one of the first to show that Omicron is less likely to result in COVID-19 hospitalization than Delta," researchers in the Scottish study wrote. While the findings are early observations, "they are encouraging," the authors wrote.
The findings have not yet been reviewed by other experts, the gold standard in scientific research.
Ascano noted the studies have limitations. For example, the findings are specific to a certain point in time during a quickly changing situation in the United Kingdom and other countries may not fare the same way.
Matthew Binnicker, director of clinical virology at Mayo Clinic in Rochester, Minnesota, said that in the Scottish study, the percentage of younger people was almost twice as high for the Omicron group compared with the Delta group, and that "could have biased the conclusions to less severe outcomes caused by Omicron."
He nonetheless said the data were interesting and suggest Omicron might lead to less severe disease. But he added: "It's important to emphasize that if Omicron has a much higher transmission rate compared to Delta, the absolute number of people requiring hospitalization might still increase, despite less severe disease in most cases."
Data out of South Africa, where the variant was first detected, have also suggested Omicron might be milder there. Salim Abdool Karim, a clinical infectious disease epidemiologist in South Africa, said earlier this week that the rate of admissions to hospitals was far lower for Omicron than it was for Delta.
"Our overall admission rate is in the region of around 2 percent to 4 percent compared to previously, where it was closer to 20 percent," he said. "So even though we're seeing a lot of cases, very few are being admitted."
The Associated Press contributed to this report.
