Omicron causes only a quarter of the deaths of patients as previous Covid waves, the first major study into mortality data suggests.

Researchers at the University of Pretoria and the National Institute of Communicable Diseases in South Africa followed patients admitted to a large hospital in City of Tshwane. The city is in Gauteng Province, the original epicentre of the omicron outbreak. 

The researchers found that 4.5 per cent died during the omicron wave, compared with 21.3 per cent before the variant took hold.

They said that, if the findings were reproduced globally, there would be a “complete decoupling of case and death rates” that would end the epidemic and usher in an endemic phase.

Although the population is younger in South Africa, which would keep death rates lower, Britain has higher levels of vaccination and seroprevalence. 

Positive data from hospitals 

Recent figures suggest the case fatality rate in Britain has fallen to 0.12 (one in 833) from highs of 3.3 (one in 30) last winter since omicron emerged, although death data will be lagged by several weeks. 

The new study also showed that those admitted to hospital in the omicron wave were discharged after an average of four days – compared with 8.8 days for previous waves – and the peak number of patients in hospital was less than half that of the delta wave.

Researchers found that 63 per cent of omicron admissions were “incidental Covid”, with people having tested positive after going into hospital for a different reason. 

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The number needing intensive care was also far lower – one per cent versus 4.3 per cent – and only one third had Covid pneumonia, of which 72 per cent had mild to moderate disease.

Fewer than half (45 per cent) of patients in Covid wards required oxygen supplementation, compared with 99.5 per cent in the first wave. The highest number of Covid beds occupied during the omicron wave was 108 on  Dec 13, much lower than the highest level of previous waves, with 213 beds having been occupied at the peak of delta on July 13.

The study involved 466 patients admitted to the Steve Biko Academic Hospital Complex from Nov 14, who were compared with 3,976 Covid patients admitted before that date. The researchers said there had been a clear decoupling of cases, hospitalisations and deaths compared with previous waves.

From epidemic to endemic 

Writing in the International Journal of Infectious Diseases, they concluded: “There was decreased severity of disease in the omicron-driven fourth wave in City of Tshwane, its first global epicentre, with fewer deaths, ICU admissions and a shorter length of stay. 

“There are clear signs that case and admission rates in South Africa may decline further over the next few weeks. 

“If this pattern continues and is repeated globally, we are likely to see a complete decoupling of case and death rates, suggesting that omicron may be a harbinger of the end of the epidemic phase of the Covid pandemic, ushering in its endemic phase.”

The researchers found that the average age for admissions was significantly lower during the omicron wave – 39 compared with 49 – which is likely to have helped keep down deaths. 

They said high levels of prior infection and vaccination had helped change the clinical presentation of the virus, but added that they could not rule out that the variant was inherently less severe. 

Around 66.7 per cent of people in City of Tshwane carry antibodies to Covid, even though only 36 per cent of adults aged 18 to 49 and 58 per cent of over-50s have been vaccinated.