Two doses of a COVID-19 vaccine are not enough to stop you catching the Omicron variant, United Kingdom (UK) scientists have warned.
Early analysis of UK Omicron and Delta cases showed the vaccines were less effective at stopping the new variant. However, a third booster dose significantly increased protection to around 75%.
The UK Health Security Agency said vaccines were still likely to offer good protection against severe COVID-19 that needed hospital treatment.
The concern since the heavily mutated Omicron variant first emerged was that it would make vaccines less effective.
Scientists analysed data from 581 Omicron cases and thousands of Delta cases to calculate how effective the vaccines were against the new variant.
It showed a dramatic drop in effectiveness for the Oxford-AstraZeneca vaccine and a significant drop off for two doses of Pfizer.
However, the third dose increased the protection against getting COVID-19 symptoms to between 70 and 75%.
The UKHSA estimates that more than half of all cases in the country will be Omicron by the mid-December and that if that growth continues unabated there will be more than one million infections by the end of the month.
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.”
“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.”