Confusing information over who was eligible for a Covid jab led to huge crowds forming in central London, public health authorities say.
Pictures and footage showed hundreds crammed shoulder-to-shoulder as people queued for a vaccine bus in Chinatown after free jabs 'without an appointment' were advertised.
Police were drafted in to control crowds on Thursday evening as lines grew.
Health authorities said incorrect guidance and incomplete information about who was eligible to use the mobile jab van's services had led to the queues forming.
An advert had been posted on the Chinese Information and Advice Centre website which welcomed 'undocumented migrants' to get the jab no NHS number or proof of identity was needed.
It read: "A Vaccine Bus is available in London Chinatown to offer free vaccine jab to the Community without appointment. Date: 27 May 2021 (Thursday) Time: 12 – 5pm.
"You DO NOT need to have: NHS number any proof of address personal identification Undocumented migrants also welcomed Stay safe! Get vaccinated!"
The bus is run by Westminster Council and is an official service facilitated by the Government and NHS.
It visited Chinatown in Soho on Wednesday and is due to visit the Portobello Road area of Notting Hill on Friday from 10am.
Local health authorities and the council said the large crowds had created capacity issues, leading to a revised system being put in place.
A spokesperson for North West London Clinical Commissioning Group (NWLCCG) said a local community organisation promoted the vaccine bus but forgot to include the detail that vaccination was only open to people over 30.
"The other information they provided was accurate and they were obviously trying to support the event in a helpful way, but the fact people thought it was open to anyone led to a far bigger attendance than anticipated," the spokesman added.
IDs are not required to get a jab, and vaccination hub staff are able to help people who don't know their NHS number when they arrive for their appointment.
The van's presence in Chinatown on Thursday attracted an anti-vax protest.
A group of women were filmed chanting “shame on you” at people onboard the bus as hordes showed up urging the crowds to reject the jab.
Experts believe the virus does not spread as easily outdoors, which informed UK Government lockdown guidance in the latter stages of the pandemic allowing mingling outdoors in parks and beer gardens before indoors restrictions eased.
However scientists have warned there is still a risk airborne virus droplets spreading at close quarters outside.
People queuing for vaccines around the UK are urged by the NHS to space themselves two metres apart.
The NWLCCG spokesman added: “The offer of the Covid vaccine is only available to people over the age of 30 and those in the priority groups as set by the Joint Committee on Vaccination and Immunisation.
“Getting the vaccine is the single most important step we can take to protect ourselves, our families and our communities against COVID-19 and we remain committed to working with the local community to ensure all those who are eligible can receive their vaccine – if you are eligible please book your jab.”
A spokesman for Westminster Council said: “We are committed to supporting the NHS and making the vaccine available to all communities within Westminster.
"The vaccine bus will make it easier to reach the heart of our diverse communities, providing the opportunity of a life-saving vaccine to everyone.”
The vaccine extended to 30-year-olds this week, as the UK's rollout passed 38million.
It comes as the surge in infection in some emerging new coronavirus hotspots sparks worries the next stage of the roadmap out of lockdown could be delayed.
The next few weeks will be crucial in determining whether coronavirus restrictions in England can be lifted on June 21, experts have said.
Current official data suggests that although hospital admissions are rising in some parts of the country affected by the Indian variant such as Bolton, Bedford, and Blackburn with Darwen - overall admissions remain broadly flat.
Some experts on Friday argued that restrictions should remain in place until more of the population have received both vaccine doses.
Prime Minister Boris Johnson said on Thursday he "didn't see anything currently in the data" to divert from the June unlocking target.
However he added a note of caution, telling reporters: "We may need to wait.
- Eligible adults can book their vaccine via the NHS website here.
