Analysis: smaller proportion of people hospitalised with Covid variant means little when rise in infections is so huge, warn experts
Last modified on Fri 24 Dec 2021 00.12 EST
Evidence that infections caused by Omicron may be less severe than other Covid variants is good news but is likely to make little or no difference to the duration of the pandemic, according to experts.
Several pieces of research published this week suggest that people infected with Omicron are much less likely to require hospitalisation.
Those with the variant are estimated to be between 31% and 45% less likely to attend A&E compared with the Delta variant, and 50% to 70% less likely to be require admission to hospital, the UK Health Security Agency (UKHSA) said on Thursday.
Separately, researchers at the University of Edinburgh studied infections from the Delta and Omicron variants since November and said the results “suggest that Omicron is associated with a two-thirds reduction in the risk of Covid-19 hospitalisation when compared with Delta”.
But experts warned that the results suggested no change in the level of infection. In the UK, the huge surge in cases – with another 119,789 new infections reported on Thursday – means that even if only a small proportion of people with Covid need to attend hospital, it could cause difficulties for the NHS.
Mark Woolhouse, a professor at the University of Edinburgh and one of the co-authors of the Scotland study, said the weight of new research meant that projections would be less pessimistic, although Omicron’s rapid spread meant there were still dangers ahead.
“It’s good but it doesn’t get us out of the woods. Severity of infection is clearly very important but it is only one factor in terms of the public health burden,” Woolhouse said, speaking in a personal capacity.
“The other thing is the sheer size of the wave. The simple way of looking at that, according to our data in Scotland, is an Omicron infection is about one-third as severe or likely to put you in hospital as a Delta infection. But if there are three times as many cases, then we are back where we started.
“We should still be worried about the sheer size of the wave, the very fast growth rates, very fast doubling time. These peak numbers of cases that we have seen in the UK are still climbing, so it is the size of that wave that is worrying people most at the moment.”
Dr Raghib Ali, a senior clinical research associate at the University of Cambridge, told Reuters that the hospital data was encouraging and “may help justify the government’s decision not to expand restrictions on social gathering over Christmas in England”.
Another scientist, who did not want to be named because of involvement in ongoing research, said Omicron infections were going to be “hugely disruptive” because of the numbers needing to self-isolate “There’s a tremendous impact on the NHS because of the workforce getting infections,” they said. “But obviously it’s good news if a smaller fraction of those infections lead to severe illness.”
Separate research published by scientists at Imperial College London found a reduction in hospital visits between Omicron and Delta cases, and estimated that those infected with Omicron were 40%-45% less likely to be hospitalised overnight than those with Delta.
But the study also suggested that two doses of a Covid vaccine were not enough to combat Omicron alone. Prof Neil Ferguson, one of the co-authors of the Imperial study, said: “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.”
Woolhouse said there remained substantial gaps in scientists’ knowledge of Omicron, such as how the UK’s booster campaign would affect the spread of infection.
“Particularly, whether [boosters] not only stop people getting ill but also stop them getting infected and passing the infection on. That would also be very helpful – at the moment we don’t know that it has much impact on the spread of these cases,” Woolhouse said.
“If it did have an impact on the spread of cases that would be further good news, and that would affect the size of the wave and therefore the public health burden.”