Older people in Wales should be told when to expect a Covid vaccination, a commissioner representing them says.
Helena Herklots says more clarity on the plan for over-80s in Wales would be "helpful" in light of different approaches elsewhere in the UK.
Former MP Ann Clwyd said many feared they were missing out as jabs were being given out in parts of England.
The Welsh Government says health boards are beginning to invite some people over the age of 80 for vaccination.
The priority list puts vulnerable people into nine groups. Priority one is care home residents and staff, with priority two being people over 80 along with front-line health and care workers.
Defending the Welsh Government's handling of the vaccine rollout, Health Minister Vaughan Gething said on social media the vaccine programme is "not stuttering in Wales" and was ahead of England per-head of population.
Mr Gething said: "I appreciate some people will be concerned but I can say categorically that people in Wales are not being left behind."
Ms Herklots said older people wanted the vaccine as soon as possible and "a great deal of work" was going into to rolling out the vaccine "quickly and effectively".
"Given reports in the past few days about the different approaches being taking to deliver the vaccine in different parts of the UK, and the potential confusion this could cause, it would be helpful for the Welsh Government to provide further information to older people about its plans, clearly setting out what the arrangements will be and when they can expect to be vaccinated," the commissioner said.
Ms Clwyd, 83, who was Labour MP for Cynon Valley for 35 years, has also called for clarity.
"People are very afraid and they want assurances. They want to know what is happening," she told BBC Wales.
"I know people around me who are more elderly than I am, and ill, and they've had no notification at all.
"They're hearing what's happening in England and they think everybody's getting the vaccine apart from them."
A Welsh Government spokesperson said: "The safety and protection of the most vulnerable people is at the heart of our response to the pandemic.
"Health boards are starting to invite some people over 80 for vaccination now. We are hoping the second vaccine - the Oxford-AstraZeneca vaccine - will be approved by the UK regulator as this will help us accelerate our vaccination programme and provide more clinics in primary care settings, like GP practices."
Across Wales more than 25,000 people have received the first of two doses of the vaccine.
Currently only one vaccine, BioNTech/Pfizer, has been approved for use in the UK.
We can now see for the first time the breakdown of the numbers of people in Wales on the priority list for vaccines.
They include more than 40,000 people living or working in care homes, thousands of front-line NHS and social care staff and the 174,000 people aged over 80.
Included are 84,000 adults classed as "extremely vulnerable".
More than 1.4 million people in all belong to one of the nine priority groups - including the overlap of about 192,000 people who may belong to more than one group.
This leaves another one million or so people under 50, without a risk condition, who will be in line eventually to receive a vaccine.
'Public will lose confidence'
Welsh Conservative health spokesman Andrew RT Davies called on the Welsh Government to "get a grip".
"The vaccination programme is stuttering into life in Wales with some real concerns around lack of access for care homes and the over 80s compared to other parts of the UK," he said.
"To keep confidence Welsh Labour ministers need to get a grip. Otherwise, there is a risk, given the scale of the vaccination programme, the public will lose confidence in the Welsh Government's ability to deliver it, replicating their shambolic handling of the virus to date."
Plaid Cymru Member of the Senedd Dai Lloyd also criticised "a dearth of information about vaccine rollout for the over-80s, which only adds to the anxiety people are facing over this Christmas".
Dr Lloyd, who is a GP, added: "Reports suggest that other UK nations are well ahead of us in Wales, which is an unacceptable situation.
"To reflect Wales's older population, Plaid Cymru had called for vaccines to be allocated according to need, not simply allocated by population. The UK and Welsh Government must urgently reassess whether Wales is getting its fair share."