The report says that tougher restrictions may be needed to prevent a wave of the new variant, which emerged in South Africa, causing anywhere between 25,000 to 75,000 deaths in England over the next five months.
But the scientists said there is still uncertainty around the modelling.
Experts from the London School of Hygiene & Tropical Medicine (LSHTM), who also sit on the Scientific Pandemic Influenza Group on Modelling (SPI-M) or the Scientific Advisory Group for Emergencies (Sage), used experimental data to look at how Omicron may transmit as the country heads into 2022, and predicted a large wave of infections in January.
The study, has not yet been peer-reviewed, does not say what will happen for definite with Omicron but gives a range of possible outcomes.
What is their optimistic scenario on Omicron?
Even under the most optimistic scenario (low immune escape of Omicron from vaccines and high effectiveness of booster jabs), a wave of infection is projected which could lead to a peak of more than 2,000 daily hospital admissions, with 175,000 hospital admissions and 24,700 deaths between December 1 this year and April 30, 2022.
This is if no additional control measures are implemented over and above the current Plan B introduced by the Government in England. There are currently about 730 deaths per week.
The team said mask-wearing, working from home and booster jabs may not be enough, and predict a peak of daily hospital admissions of 2,400 in January. At present there are about 680 admissions per day.
In this optimistic scenario, bringing in control measures early in 2022 – such as restrictions on indoor hospitality, the closure of some entertainment venues and restrictions on how many people can gather in one place – would be sufficient to substantially control the wave, reducing hospital admissions by 53,000 and deaths by 7,600.
What is their pessimistic scenario on Omicron?
The most pessimistic scenario (high immune escape from vaccines and lower effectiveness of boosters) projects a wave of infection which is likely to lead to a peak in hospital admissions around twice as high as the peak seen in January 2021, if no additional control measures are taken.
This could cause 492,000 hospital admissions and 74,800 deaths, according to the study.
In this scenario, the team estimates that stronger measures may be required to keep the peak number of hospital admissions below the January 2021 peak.
The scientists assumed Omicron causes the same severity of illness as Delta but did not look at the impact of measures such as mass population testing to control its spread.
What did the scientists say?
They said in their paper: “These results suggest that Omicron has the potential to cause substantial surges in cases, hospital admissions and deaths in populations with high levels of immunity, including England.
“The reintroduction of additional non-pharmaceutical interventions may be required to prevent hospital admissions exceeding the levels seen in England during the previous peak in winter 2020–2021.”
Dr Rosanna Barnard, from LSHTM’s Centre for the Mathematical Modelling of Infectious Diseases, who co-led the research, said: “More data over the next few weeks will strengthen our knowledge on Omicron and the consequences of this on transmission in England.
“However, these early projections help guide our understanding about potential futures in a rapidly-evolving situation.
“In our most optimistic scenario, the impact of Omicron in the early part of 2022 would be reduced with mild control measures such as working from home.
“However, our most pessimistic scenario suggests that we may have to endure more stringent restrictions to ensure the NHS is not overwhelmed.
“Mask-wearing, social distancing and booster jabs are vital, but may not be enough.
“Nobody wants to endure another lockdown but last-resort measures may be required to protect health services if Omicron has a significant level of immune escape or otherwise increased transmissibility compared to Delta.
“It is crucial for decision-makers to consider the wider societal impact of these measures, not just the epidemiology.”
Dr Nick Davies from CMMID, who co-led the new study, said: “These are early estimates, but they do suggest that, overall, Omicron is outcompeting Delta rapidly by evading vaccines to a substantial degree.”
He told a briefing “the booster programme will substantially mitigate the impact of Omicron in England”.
Dr Davies added that it was difficult to predict the true level of protection offered by two doses of AstraZeneca and Pfizer, and urged people to get boosters.
Yesterday, the UK Health Security Agency warned that the Omicron strain is expected to become the dominant variant in the UK by mid-December.
Analysis of 581 people with confirmed Omicron cases showed the AstraZeneca and Pfizer vaccines provided “much lower” levels of protection against Omicron when compared with the Delta variant.
But the HSA said that preliminary data showed vaccine effectiveness “considerably increased” in the early period after a booster dose, providing around 70 to 75% protection against symptomatic infection.
Methodology of the study
The scientists made assumptions about the levels of transmissibility and immune escape of Omicron using “S” gene target failure (SGTF) data from cases in England.
These are cases that are highly likely to be Omicron because the SGTF occurs with Omicron but not the Delta variant.
For the two immune escape scenarios considered, the team estimated the Omicron variant to be between 10% less transmissible than the Delta variant to 35% more transmissible than Delta.Some experts have already said Omicron is more transmissible and many expect it to rapidly overtake Delta as the dominant variant.
This article was originally published on our sister title, NationalWorld