LONDON: Prime Minister Boris Johnson issued a "call to get jabs in arms" on Wednesday as Britain stepped up its COVID-19 booster programme to fend off the Omicron variant of concern.

Britain has recorded 22 cases of the new variant, which appears to be more transmissible. It announced a new target this week to offer all adults a booster shot by the end of January, which means speeding up its booster programme by an extra million doses a week.

Johnson said Britain had delivered the fastest vaccine rollout in Europe earlier this year, and with the emergence of the Omicron variant people needed to come forward again.

"This isn't a call to arms, but a call to get jabs in arms. And quickly," he said on Twitter.

First reported in southern Africa a week ago, Omicron has spread to more than a dozen countries, spooking financial markets. Governments have responded by reintroducing some travel restrictions.

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British Health Secretary Sajid Javid said booster vaccines would help protect against severe disease from Omicron, even if it turns out the shots are not as effective against the variant as against previous strains of the disease.

Government data shows 81% of the population aged over 12 have had two doses of vaccine, while 32% have had a booster shot, or third dose.

Johnson said on Tuesday that vaccinations would be ramped up to levels seen earlier in the year, when 3.5 million shots were being delivered a week. In the last week, Britain vaccinated about 2.4 million people, Javid said.

"We need to increase that by around a million a week, but I think it can be done to give everyone an offer by January."

Payments to local doctors, community pharmacies and hospitals will increase to 15 pounds ($20) per dose until the end of January, the government said.

Local doctors, however, have voiced concerns that the focus on boosters could divert resources from efforts to clear backlogs of treatments unrelated to COVID-19, built up during earlier lockdowns.

"We're simply not going to be able to do everything we're doing at the moment," Gary Howsam, vice chair of the Royal College of General Practitioners, told Times Radio.