Long queues formed at a vaccine centers in England on Tuesday as hundreds of thousands of people rushed to get COVID booster shots after Prime Minister Boris Johnson warned that the Omicron variant could overcome the immunity of the inoculated.

The National Health Service said 704,148 vaccine appointments were made on Monday, including 655,170 for boosters.

Hundreds queued up at a walk-in vaccination center at Saint Thomas' Hospital in London and at other centers across England, Reuters photographers said.

"Vaccination sites have been asked to operate 12 hours a day, seven days a week wherever possible and in every community, there should be slots available at least 16 hours a day," said Dr Emily Lawson, director of the NHS COVID-19 vaccination program.

There were, though, problems ordering lateral flow tests - which will be required for some social gatherings - for home delivery.

"There are no rapid lateral flow tests available to order today for home delivery," the government's website said.

Jonson's Omicron Warning to Top Ministers

Johnson warned his top ministers Tuesday a "huge spike" in cases of the Omicron coronavirus variant was on its way and that the government must press on with its booster jab program.

"The PM [prime minister] said a huge spike of Omicron was coming and the measures we aim to introduce as part of plan B were balanced and proportionate, helping to reduce transmission while we ramp up the booster program," his spokesman told reporters after Johnson met his cabinet team.