While countries are racing to administer booster shots to protect against the Omicron variant of Covid-19, a new study released by the UK Health Security Agency (UKHSA) has shown that protection wanes even after taking the third dose of a vaccine within 10 weeks.

Scientists at the UKHSA noted that protection against Omicron appears to wane more rapidly than Delta among people who are boosted. They found 15 to 25 per cent reduction after 10 weeks.

"Repeated vaccine effectiveness analysis continues to show lower for symptomatic Omicron disease compared to Delta. There is evidence of waning of protection against symptomatic disease with increasing time after second dose, and by 10 weeks after the booster dose, with a 15 to 25 per cent reduction in vaccine effectiveness after 10 weeks," the UKHSA wrote in its latest technical brief.

"This waning is faster for Omicron than for Delta infections.

"However, vaccine effectiveness against severe disease is more likely to be sustained, especially after a booster dose, the brief said.

The team also said that neutralisation data, real world vaccine effectiveness against symptomatic disease, and reinfection rate all confirm substantial immune evasion properties in the case of Omicron.

Further, the study showed that the risk of hospital admission for a person detected as a case of Omicron appears reduced compared to a case of Delta.

However, health officials believe it's unlikely that these individuals are at a greater risk of severe illness. As a whole, people who catch Omicron are 50 to 70 per cent less likely to need hospital care compared to previous variants, the analysis showed.

The UK has reported a record 1,19,789 daily Covid-19 cases as on Thursday, the second time daily cases have risen above 1,00,000, according to the UKHSA. The country has also seen 14 deaths so far due to Omicron.

Britain is also considering the rollout of a fourth round of vaccination against Covid-19 after both Israel and Germany gave the green light to a second set of boosters. Experts on the Joint Committee on Vaccination and Immunisation will examine evidence on levels of immunity given by three jabs as well as data on hospitalisations for the new Omicron variant before making any decision on a fourth vaccine dose.