Estimates suggest Omicron cases are 15% less likely to attend hospital, and 40% less likely to be hospitalised for a night or more, compared to Delta.
Researchers at Imperial College London stress that these estimated reductions in severity must be balanced against the larger risk of infection with Omicron, due to the reduction in protection provided by both vaccination and natural infection.
For example they say, at a population level, large numbers of infections could still lead to large numbers of hospitalisations.
Their estimates will assist in refining mathematical models of potential healthcare demand associated with the unfolding European Omicron wave.
The estimates suggest that Omicron cases have, on average, a 15-20% reduced risk of any hospitalisation and an approximately 40-45% reduced risk of a hospitalisation resulting in a stay of one or more nights.
Reinfection is associated with approximately a 50-60% reduction in hospitalisation risk compared with primary infections.
Moderately reduced severity is also supported by the observation that the mean lengths of hospital stay for Delta and Omicron cases in the study were 0.32 and 0.22 days, respectively.
Professor Neil Ferguson from Imperial College London said:
“Our analysis shows evidence of a moderate reduction in the risk of hospitalisation associated with the Omicron variant compared with the Delta variant. However, this appears to be offset by the reduced efficacy of vaccines against infection with the Omicron variant. Given the high transmissibility of the Omicron virus, there remains the potential for health services to face increasing demand if Omicron cases continue to grow at the rate that has been seen in recent weeks.”
Professor Azra Ghani from Imperial College London said: “Whilst the reduced risk of hospitalisation with the Omicron variant is reassuring, the risk of infection remains extremely high. With the addition of the booster dose, vaccines continue to offer the best protection against infection and hospitalisation.”
Meanwhile another study in Scotland has been tracking coronavirus and the number of people ending up in hospital.
It found that if Omicron behaved the same as Delta, they would expect about 47 people to have been admitted to hospital already. At the moment there are only 15.
