A booster dose of a Covid-19 vaccine reduces the risk of hospitalisation with the Omicron variant by 81 per cent, new data from the UK suggests.
Unvaccinated people with Omicron are up to eight times more likely to end up in hospital than those who are boosted, the data showed, as Britain experiences a surge in cases driven by the highly-transmissible variant - with record daily infections of 189,846 reported on Friday.
The risk of hospitalisation with the Omicron variant is about one-third that of the Delta variant, according to analysis of more than a million cases of both types in Britain in recent weeks.
While hospital admissions have started to rise in the UK, the government has said it believes the new variant is milder than the Delta variant.
The number of patients needing mechanical ventilation beds has also remained steady through December, unlike previous peaks in the pandemic.
Protection against infection
The analysis was published by the UK Health Security Agency, after it worked alongside the Cambridge University MRC Biostatistics unit to analyse 528,176 Omicron cases and 573,012 Delta cases.
It found there is no effect against symptomatic infection with the Omicron variant 20 weeks after a second dose of the AstraZeneca vaccine. Vaccine effectiveness also waned over the same period of time in the Pfizer and Moderna jabs, down to 10 per cent.
However, around two to four weeks after a booster jab, vaccine effectiveness against symptomatic infection ranged from around 65-75 per cent, down to 55-70 per cent five to nine weeks on, and down to between 40 and 50 per cent from 10 or more weeks after the third dose, the UKHSA said.
However, the organisation said just one dose of any vaccine was associated with a 35 per cent reduced risk of hospital admission among symptomatic cases with Omicron, with protection against hospitalisation highest after a third booster dose.
The risk of hospitalisation is lower for Omicron cases with symptomatic or asymptomatic infection after two and three doses of vaccine
"In this analysis, the risk of hospitalisation is lower for Omicron cases with symptomatic or asymptomatic infection after two and three doses of vaccine, with an 81 per cent ... reduction in the risk of hospitalisation after three doses compared to unvaccinated Omicron cases," the UKHSA said.
Susan Hopkins, Chief Medical Adviser at the UKHSA, said the analysis was in keeping with other encouraging signs on Omicron but said the health service could still struggle with such high transmission rates.
"It remains too early to draw any definitive conclusions on hospital severity, and the increased transmissibility of Omicron and the rising cases in the over 60s population in England means it remains highly likely that there will be significant pressure on the NHS in coming weeks," she said.
Friday's daily data update showed 12,395 patients in hospital in England with Covid-19, up from 11,542 on Thursday and continuing a steeply rising trend. However, the figure is well below a peak of more than 34,000 in January.