The findings released on Friday are some of the earliest data on the protection against Omicron outside of lab studies, which have shown reduced neutralising activity against Omicron.
The early real-world data suggest that while Omicron could greatly reduce the protection against mild disease from an initial two-dose vaccination course, boosters restored the protection to an extent.
“These early estimates should be treated with caution but they indicate that a few months after the second jab, there is a greater risk of catching the Omicron variant compared to Delta strain,” Mary Ramsay, head of immunisation at the UKHSA said on Friday, adding that protection against severe disease was expected to remain higher.
“The data suggest this risk is significantly reduced following a booster vaccine, so I urge everyone to take up their booster when eligible.”
In an analysis of 581 people with confirmed Omicron, two doses of AstraZeneca and Pfizer-BioNTech vaccines provided much lower levels of protection against symptomatic infection compared with what they provide against Delta.
However, when boosted with a dose of Pfizer vaccine, there was about 70 percent protection against symptomatic infection for people who initially received AstraZeneca, and about 75 percent protection for those who received Pfizer.
That compares to estimated protection against infection from Delta following a booster of about 90 percent.
UKHSA said, at current trends, Omicron would account for more than 50 percent of all COVID-19 infections by mid-December, with the UK exceeding one million infections by the end of the month.
On Thursday, the World Health Organization expressed concerns that rich countries spooked by the emergence of the Omicron variant could step up the hoarding of COVID-19 vaccines and strain global supplies again, complicating efforts to stamp out the pandemic.
The UN health agency, after a meeting of its expert panel on vaccination, reiterated its advice to governments against the widespread use of boosters in their populations so that well-stocked countries instead can send doses to low-income countries that have largely lacked access to them.
Source: Al Jazeera