Two doses of the AstraZeneca and Pfizer/BioNtech vaccines offer little protection against the Omicron variant of COVID, but a booster raises their effectiveness to between 70 and 75 percent.
The UK Health Security Agency also said the country will have more than one million Omicron cases by the end of this month if current trends continue unchanged.
Analysis of 581 people with confirmed Omicron showed the AstraZeneca and Pfizer/BioNtech jabs provided “much lower levels of protection against symptomatic infection compared to the protection that they provide against Delta”, it said in a statement.
But it added: “The preliminary data showed effectiveness against the new variant appears to increase considerably in the early period after a booster dose, providing around 70-75% protection against symptomatic infection.
“Due to the early nature of the findings, all estimates are subject to significant uncertainty and are subject to change.”