Omicron is causing milder disease than Delta in patients in the epicentre of the new Covid variant, the first major real-world study in South Africa confirmed today.
Officials who analysed 78,000 Omicron cases in the past month estimated the risk of hospitalisation was a fifth lower than with Delta and 29 per cent lower than the original virus.
As a crude rate, Omicron is currently leading to a third fewer hospital admissions than Delta did during its entire wave — 38 admissions per 1,000 Omicron cases compared to 101 per 1,000 for Delta.
The findings lend weight to the theory that the ultra-infectious variant is weaker than previous strains, something which doctors on the ground in South Africa have been claiming for weeks.
But the reduction in severity is probably not solely down to Omicron being intrinsically milder, according to the South African Medical Research Council which led the analysis.
Around 70 per cent of South Africans have recovered from Covid already and 23 per cent are double-vaccinated, which has created high levels of immunity.
The finding will raise hopes that the UK's Omicron wave will be less severe than previous peaks, despite having an older and denser population. Unlike South Africa, the UK is rolling out booster jabs on a mass scale.
The study also found two doses of Pfizer's vaccine still provide 70 per cent protection against hospital admission or death from Omicron, compared to 93 per cent for Delta.
While this is more protection than many scientists initially feared, it still leaves 30 per cent of people vulnerable to severe Omicron disease, four times as many as Delta. Waning immunity from two Pfizer doses was found to offer just 33 per cent protection against Omicron infection, explaining why the country has seen a meteoric rise in case numbers.
Despite the optimism, No10 was warned today by chief medical officer Professor Chris Whitty there will be a a 'significant increase in hospitalisations' from Omicron in the coming weeks. UK experts are concerned that different demographics in Britain make the country more susceptible to high infection numbers and hospital pressure.
Officials who looked at 78,000 Omicron cases in the past month found t he risk of hospitalisation was a fifth lower than with Delta (in green) and 29 per cent lower than the original virus (dark blue). Omicron is shown in brown and the original South African 'Beta' variant in light blue. Children appeared to have a 20 per cent higher risk of hospital admission with complications during the new wave than the initial outbreak, despite the numbers still being tiny
As a crude rate, Omicron is currently causing a third fewer hospital admissions than Delta did during its entire wave — 38 admissions per 1,000 Omicron cases, compared to 101 per 1,000 for Delta
The study also found that two doses of Pfizer's vaccine still provides 70 per cent protection against hospital admission or death from Omicron, compared to 93 per cent for Delta
Waning immunity from two Pfizer doses was found to offer just 33 per cent protection against Omicron infection, explaining why the country has seen a meteoric rise in case numbers
Against Delta, two Pfizer jabs initially offer more than 80 per cent protection against symptomatic infection before falling to around 60 per cent within six months.
Today's study, co-run by private health insurance company Discovery Health, was based on more than 211,000 positive Covid test results from November 15 to December 7, 78,000 of which were attributed to Omicron.
Overall, four in 10 of those who tested positive had received two doses of the Pfizer/BioNTech vaccine.
The 70 per cent protection from severe disease figure still puts two doses well above the World Health Organization's efficacy threshold of 50 per cent.
But the researchers said that efficacy was reduced further in older age groups, falling to just 59 per cent in the 70 to 79 bracket, for example.
That could be because older people were vaccinated first in the initial rollout and there has been more time for immunity to wane than in younger people.
Protection against admission was consistent across a range of chronic illnesses including diabetes, hypertension, hypercholesterolemia, and other cardiovascular diseases, the study said.
Children appeared to have a 20 per cent higher risk of hospital admission with complications during the fourth wave than during the first, despite the numbers still being tiny.
'This is early data and requires careful follow up,' said Shirley Collie, chief health analytics actuary at Discovery Health.
She cautioned that children were still 51 per cent less likely to test positive during the Omicron wave and the risk for them remains low.
As a crude rate, Omicron is currently causing a third fewer hospital admissions than Delta did — 38 admissions per 1,000 Omicron cases, compared to 101 per 1,000 for Delta.
However, South Africa is only a month into its Omicron outbreak and Covid admissions are steadily rising, with 422 admitted yesterday, a rise of 141 per cent compared to last week.
A total of 6,198 people are being treated for the virus now compared to the 5,562 who were in hospital on Sunday — the biggest single-day rise since the new variant took off.
Yet, despite the increasing case and hospital numbers, there were just 11 deaths attributed to Covid in the last 24 hours, up only marginally on last week.
Doctors in South Africa's Omicron ground zero maintain that Omicron patients are coming in with milder illness and being discharged quicker.
Official figures suggest the number of Covid hospital patients with severe illness is a third of the level at the same point in the country's Delta wave.
The South African doctor who first raised the alarm about Omicron last month endorsed the study today, telling MPs that it confirmed what doctors were seeing on the ground.
Dr Angelique Coetzee, chairwoman of the South African Medical Association, told the Commons Science and Technology Committee that 'we don't have all the answers'
