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People who are infected with the omicron variant have a 36% lower risk of being admitted to the hospital than those who are infected with the delta variant. It shows a new analysis that Statens Serum Institut (SSI) has done together with a large number of partners.

Image by Alexandra_Koch from Pixabay

The study has been submitted to a scientific journal and has not yet been peer-reviewed but published in a pre-print version.

The study included a total of 188,980 individuals who tested positive for SARS-CoV-2 in the period from November 21 to December 19, 2021. That is, in the period when almost all PCR-positive samples were screened for omicron by variant PCR and / or by whole genome sequencing.

All registry data – including admissions information – was updated on January 4, 2022.

Among the 188,980 people, 38,669 were infected with omicron, while the rest are estimated to have been infected with delta. Among the 38,669 infected with omicron, 222 were hospitalized (0.6%). Looking at the 150,311 delta cases instead, 2,213 were admitted (1.5%).

When one takes into account the differences in, among other things, age, sex and underlying diseases in the two groups, one finds that there is a 36% (95% safety interval: 25-44%) less risk of hospitalization among those infected with omicron in relation to delta.

The study also shows that the risk is significantly reduced in all groups of vaccination status. That is, both for those who have not been vaccinated, those who have received the 2nd vaccine, and those who have received the 3rd vaccination.

“There is more good news in this study. First, we find a 36% lower risk of being admitted with omicron compared to delta. We do this among both unvaccinated and vaccinated. This is a sign that omicron in itself is less serious than a delta “, says professional director Tyra Grove Krause from SSI.

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The study also found a generally lower risk of hospitalization among individuals who had tested positive and were vaccinated (with both 2nd and 3rd stings) compared to unvaccinated. In total, the risk was 75% lower (95% safety range: 73-78%).

“In addition, over the study period, we can see that vaccination can prevent three out of four admissions – both omicron- and delta-related – among people who test positive. This shows that part of the decoupling between infection rates and hospitalization rates is due to the new variant, but that it is even more so due to the high vaccination status, ”continues Tyra Grove Krause.


Decoupling is the situation that we no longer experience the same relationship between infection and hospitalizations as before.

The new study only examines the risk of hospitalization after omicron infection compared to delta infection.

“Based on data from the study, it is still too early to conclude on the severity of the admission itself. Including the length of hospital stay and the risk of being admitted to intensive care, ”says Tyra Grove Krause. She continues:

“However, several studies from abroad indicate that omikron is also associated with a milder course of hospitalization, assessed on the basis of the shorter hospital stay and less risk of intensive care and death compared to delta.”