An NHS trust has opened walk-in services at its Covid mass-vaccination centres after one hub was reported to be operating at well below capacity.
Eligible patients no longer need an appointment to attend hubs in Newport, Basingstoke, Portsmouth and Southampton, Solent NHS Trust said.
A worker at the St James' Hospital site in Portsmouth said it had been "staggeringly" under-used.
The trust said it had reviewed the service to make access more convenient.
Its four large-scale vaccination centres have been operating 12 hours a day, seven days a week.
However, a worker at St James' Hospital said it was "staggeringly quiet" with staff sometimes being sent home early.
The walk-in service is operating for a trial period of seven days between 12:30 and 15:30 GMT.
The worker, who asked not to be named, said: "The set-up is amazing, world-class, really well-organised, but it's tragic to see how few people are going in.
"Last week someone rang the local police and they came in droves [for vaccinations]."
The worker said the unit had treated 200 patients on some days, although its capacity was about 1,000.
In a press release, Solent NHS Trust said the new walk-in service was being "offered to people in line with recommendations from the JCVI [the government's Joint Committee on Vaccination and Immunisation]".
It said people aged 64 and over, those in receipt of Carer's Allowance and the clinically extremely vulnerable would be able to receive vaccinations by bringing proof of eligibility.
Chief operating officer David Noyes said: "This... will help us to vaccinate even more people with the highest need quicker."
Previously, an MP said a mass vaccination hub in Bournemouth was under-used because of competition from GP surgeries.
Tobias Ellwood, Conservative MP for Bournemouth East, said GPs were "discouraging" patients from using the centre so they could receive payments for administering the jabs themselves.