Studies from Great Britain: New Evidence for Mild Omicron Gradients

Researchers call the results “encouraging”: Two British studies seem to confirm the South African observations of milder Omicron disease courses. Nevertheless, the experts warn against rash hopes.

Two studies from Great Britain suggest that infection with the Omicron variant of the coronavirus seems to lead to milder disease courses than the Delta variant. An estimate by the Covid-19 research team at Imperial College London found that the likelihood of hospital admissions for Omicron cases in England is around 20 percent lower than for infections with the Delta variant. The risk of ending up in hospital for one night or longer with an Omicron infection is 40 percent lower than with Delta, it said.

For the analysis, the London researchers evaluated all infections confirmed by PCR tests in England in the first half of December in which the variant could be detected. 56,000 Omicron cases and 269,000 Delta cases were represented.

Azra Ghani, who co-authored the study, said: “The reduced risk of hospitalization with the Omikron variant is reassuring, but the risk of infection remains extremely high.” A refresh of the vaccination offers “still the best protection against infections and hospital stays.”

Scottish study with restrictions

The second study comes from Scotland. The results of the researchers at the University of Edinburgh suggest that the risk of hospitalization with Omikron is two-thirds lower than with Delta. The authors point out, however, that the almost 24,000 Omicron infections in Scotland were found in predominantly young adults between the ages of 20 and 39. Younger people have a lower risk of serious illnesses caused by Covid-19.

In addition, the authors emphasize that the findings are preliminary observations. But they are “encouraging”. At the same time, the researchers warned against rash hopes. Even if the findings of the studies were to be confirmed, one would have to weigh mild disease courses against the fact that the omicron mutant is spreading faster than Delta and is better able to bypass vaccination protection. The sheer number of Omikron infections could nevertheless overload the hospitals.

So far, none of the studies has been independently reviewed. This is common in science and actually standard. In corona research, however, studies are more often published without reports in order to make initial findings quickly accessible.

Many infections negate the effect

The studies contribute to a growing body of scientific evidence that appears to confirm a less severe course of Omicron infections. It remains unclear, however, whether the lower rate of severe cases observed is due to the characteristics of the omicron variant or whether the disease is milder because it affects populations with greater immunity from previous infections and vaccinations.

Penny Ward, Professor of Pharmaceutical Medicine at King’s College London, who was not involved in the studies, said they “did nothing to change the extraordinary prevalence of this variant in the population.” It is a fact that “even a small proportion of people who have to be treated in hospital for Covid can become a very large number if the number of infections in the population continues to rise.”

Hope already after South African studies

Previously, data from South Africa, where the variant was first discovered, had already suggested that those infected with Omikron are by and large not as seriously ill as those with Delta.

The authors of the study evaluated data from infected people from the beginning of October to the end of November. This means that Omikron has an up to 80 percent lower risk of hospital treatment than Delta. Once the patients were in the clinic, there was no difference in the further course. “The very encouraging data strongly suggest a lower severity of the omicron wave of infection,” said Cheryl Cohen of South Africa’s National Institute for Communicable Diseases (NICD). However, she warned that the data are still early and that more studies are needed.

Data cannot simply be transferred to Germany

Infectiologist Isabella Eckerle from the University of Geneva warned not to jump to conclusions from the investigation. “You also have to keep in mind that South Africa has a young population, there has been high excess mortality in the previous waves, and the cases reported have mostly been young people with breakthroughs in vaccination,” she said. “The beta variant was also increasingly circulating in South Africa, so that there is probably a different immunological background than ours.”

Björn Meyer, head of the virus evolution working group at the University of Magdeburg, made a similar statement. There are big differences between South Africa and Germany. South Africa has experienced a lot of heavy waves, the population is on average much younger. “So it remains to be seen.”