In a briefing on Friday, the UKHSA said if current trends continue unchanged, the UK will exceed one million Omicron infections by the end of the month.
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.
Booster dose provides 70-75% protection against Omicron
However, the UKHSA 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.
Dr Mary Ramsay, head of immunisation at the UKHSA, said: “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.
“The data suggest this risk is significantly reduced following a booster vaccine, so I urge everyone to take up their booster when eligible. We expect the vaccines to show higher protection against the serious complications of Covid-19, so if you haven’t yet had your first two doses please book an appointment straight away.”