Home testing kits were also unavailable
People queue outside a coronavirus disease vaccination centre at St Thomas's Hospital in London. – Reuters
Long queues of people formed at vaccine centres in major English cities on Monday after Prime Minister Boris Johnson urged all adults to get a booster shot, Reuters reporters said.
Queues formed at centres in London and Manchester in northern England. There were also issues booking appointments online.
"The Covid vaccine booking service is currently facing extremely high demand so is operating a queueing system," the National Health Service said on Twitter.
"For all others experiencing waits, we would advise trying again later today or tomorrow."
Home testing kits were also unavailable.
"Sorry, there are no more home test kits available right now," the government's official booking service said.
"Try again later. Or, you can go back and try to book a test site appointment instead."