LONDON, Jan. 11 (Xinhua) -- British Prime Minister Boris Johnson on Monday warned against "false complacency" as the country is seeking to speed up the coronavirus vaccine rollout.

"This is a very perilous moment because everybody can sense that the vaccine is coming in and they can see that the UK is vaccinating large numbers of those that need it most," he said during a visit to a vaccination center in Bristol, located in southwest England, about 193 km west of London.

"My worry is...that this is the moment when that degree of false confidence, false complacency, and that when you look at what has happened in the NHS (National Health Service) that complacency is not merited," he said.

According to the prime minister, 2.4 million coronavirus jabs have been administered across Britain.

Seven new mass vaccination sites in England opened Monday, as the country races against time to bring the pandemic under control.

Earlier Monday, Chief Medical Officer for England Chris Whitty warned that the "most dangerous time" of the coronavirus pandemic in Britain has yet to come before vaccine rollout has an impact.

The next few weeks will be "the worst" of the pandemic for the NHS, he told the BBC, urging the public to minimize all unnecessary contact with others.

Johnson and Whitty made the warnings after Britain surpassed the grim milestones of 3,000,000 COVID-19 cases and 80,000 coronavirus-related deaths on Saturday.

England is currently under the third national lockdown since the pandemic began in the country. To bring life back to normal, countries such as Britain, China, Germany, Russia and the United States have been racing against time to develop coronavirus vaccines.