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.”
“Vaccine effectiveness against severe disease from Omicron is not yet known but is expected to be significantly higher than protection against symptomatic disease,” the statement continued, adding “data on this won’t be available for several weeks.”
One million cases
On the spread of infection the UKHSA said: “It is projected that if current trends continue unchanged, the UK will exceed one million infections by the end of this month.”
It also estimated that if Omicron continues to grow at the current rate, it will “become the dominant strain, accounting for more than 50% of all COVID-19 infections in the UK by mid-December”.
It said evidence continues to show the new variant is transmitting “more rapidly than the dominant Delta variant”, with studies of households and contacts finding there is a “higher risk of transmission to contacts from an Omicron case”.
‘Early estimates should be treated with caution’
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.
“Working from home where possible, consistently wearing masks in crowded or enclosed spaces, washing your hands regularly, and isolating and getting tested if you feel unwell are also vitally important in reducing the impact of COVID-19 this winter.”
‘I urge you to come forward as soon as you’re eligible’
Reacting to the latest data, Health Secretary Sajid Javid urged people to get the booster jab.
“They are our best defence and we have turbocharged our rollout programme inviting seven million more people over the age of 40 to get their booster jab so even more people get protection from this disease,” he said.
“I urge you to come forward as soon as you’re eligible to help keep yourself and your loved ones safe.”