For over 620,000 people who have already received a dose of the vaccine against coronavirus, there is a sense of relief. For over 240,000 who are now fully vaccinated, they must feel great comfort that they are strongly protected from Covid-19.

These are the most vulnerable people and many more need to have the protection, as fast as the national vaccination programme can deliver it.

At this point, the top question on most people's mind is 'when will I be vaccinated?' It’s the only game in town now. And the success in the fight against the virus will be heavily judged on the success, or otherwise, of the national vaccination programme.

The arrival of vaccines was always going to result in a kind of vaccine wars. Battles by the EU and among countries for the fastest access to doses of vaccine. A race to be the first country to begin immunisation. Competition on who could roll-out vaccination in the fastest and most efficient way. And within countries, arguments about who should get priority over others, for immunisation.

Up to this week, Ireland had a 15-group priority list, which was agreed by Government in December, after advice from the National Immunisation Advisory Committee, endorsed by NPHET. That is now being changed to a nine-group priority list, based on age once all those over 64 years are vaccinated.  It means that the age-based system for people aged 64 and younger will be rolled out between May, June and July, mostly via mass vaccination centres.

The change caught most people by surprise on Tuesday. According to the Tánaiste, the expert advice only came moments before the Cabinet meeting this week and so there was no opportunity to engage with unions or other parties on the development.

I have confirmed that the potential for a change to an age-based vaccination system was discussed last week by the Covid-19 Oversight Group, chaired by the Secretary General to the Government, other relevant Government department secretaries, and the group also includes the HSE Chief and the deputy CMO at the Department of Health.

The issue was also discussed at the Cabinet Sub-Committee on Covid-19 on Monday night, before the full Cabinet meeting on Tuesday afternoon. The medical and scientific advice, recommending the change from the National Immunisation Advisory Committee, was also available to the Cabinet Sub-Committee meeting on Monday and to the full Cabinet.

Not surprisingly, many groups are unhappy - teachers, gardaí, special needs assistants, carers and others. The issue is likely to be hotly debated at the teachers’ conferences next week.

Part of the surprise is due to the late change to an age-based system, given that the original vaccination programme has been under way since the start of the year and we are already in April. So it has the potential to cause some confusion and anxiety for people. The change to an age-based system is said to be simpler, fairer and should mean a faster benefit for people from vaccination. It should also end the queue-jumping that has angered so many people recently.

There was much coverage this week about the Beacon Hospital vaccinating around 20 teachers from a private school, using vaccines provided by the State. The out of sequence vaccination caused uproar and an independent review is under way. Similarly, questions have been raised about how many HSE staff may have received vaccination under Category 2 - frontline health staff - when they are not frontline health staff but perhaps clerical or administrative staff.

HSE chief Paul Reid said there have been people who skipped the queue and cheated the system. But he has insisted that the number is very marginal. If the number of people involved is said to be marginal, the number must be known to make that determination. It has not been released. This Group 2 who were vaccinated are all supposed to be frontline health staff, essentially patient facing.

In total, around 127,000 people work in the HSE. Many, but certainly not all, are frontline health staff. Up to last Monday, 327,851 doses had been administered to Group 2, of which 235,418 were first doses and the balance second doses. People have asked how can this number be so high, given the total number of health staff in the HSE? Part of the answer is that you must also add in frontline staff in private hospitals, the voluntary sector, Section 39 agencies, GPs, dentists and others, which would certainly bring the number up. But would it bring it up to 235,000 people? PPS numbers and employment ID were required to get vaccinated in this group, so it should not be difficult to identify people, if the desire is there to do so. What the public is asking for is transparency.

The Social Democrats this week called for a full audit of who has been vaccinated. People will make the case that if there are consequences for the Beacon Hospital, the VHI, the Coombe Hospital and others, then equally there should be consequences for anyone in the HSE or the wider health service that got the vaccine when they should not have.

Those that have queue jumped should be identified and face consequences that others are facing. The Irish Patients Association has called on the HSE to similarly have an independent review into how many of its staff may have queue jumped vaccination and to produce the figures.

Stephen McMahon, of the Irish Patients Association had this to say.

"The HSE CEO's recent comment is that queue jumping for vaccination in the organisation is very small. So of the 235,500 doses given in the frontline health staff group, if only 0.1% - a very small percentage - were issued to people not in line, it would suggest a figure of 235 instances. That would be 10 times the Beacon level. Like the Beacon Board, has the HSE’s board met in emergency session to review this, and other matters such as double booking vaccinations?"

The rationale for the change to an age-based system is the advice from the NIAC that age is the strongest predictor of hospitalisation, admission to ICU and death. For every one person aged 19-24 years who is hospitalised by the virus, six people aged 60-64 are hospitalised.

The highest death rates for Covid-19 are in older people, those aged 80 or older, people aged 70-79 and those aged 60-69. So the appeal by the health authorities is to a sense of fairness among people.

The age-based system is being operated in Northern Ireland and in the UK. It is viewed as not just fairer, more transparent but simpler to operate also. It answers the key question - when will I be vaccinated?

Of course before the system gets to an age-based one, it has to complete the vaccinations for those over 64, the vulnerable groups, key vaccine workers and people with underlying health conditions that place them at very high risk, or at high risk of serious disease or death.

The very high risk group is Category 4. There are an estimated 150,000 to 250,000 people in this group so it is a very large body of patients. At the time of writing this, over 28,500 people in Category 4 had received a dose of vaccine. So the task ahead is huge to reach this body of patients.

At a vaccination briefing in the Department of Health this week, I asked why the vaccination of this group appeared to be going quite slowly. Dr Colm Henry, HSE Chief Clinical Officer, said that identifying some patients was proving "tricky and difficult." It was easier to identify certain patients like those with cancer, kidney disease or people on dialysis, he said.

A contributory factor is that there are few disease registers in Ireland to assist identifying patient groups. Some patients do not attend a hospital. Others attend a number of hospitals. Some patients are under a number of different specialists. Then there are the patients who only attend their GP. It has made this task difficult and I see it in emails I am receiving from patients with significant conditions worried about when they will be contacted either by their hospital, or GP.

The HSE approached the issue taking the view that the best way to start identifying those with a severe illness was through the hospital system, as that is where they would most likely be found. The less severe patients would be under GP care. The degree to which GPs will be involved in identifying this group of patients is not clear yet, as we do not know how many are willing and able to undertake this work.

GPs have been asked to prioritise around 88,000 patients in Category 4. These are certain people with diabetes, those who are obese with a Body Mass Index over 40, people with chronic respiratory disease who are at home on oxygen, pre or post transplantation or with a hospital admission related to their disease in the past year, and patients with Prader Willi syndrome.

We are now in the month when the Government has promised one million vaccinations, and the same again in May and in June, although the expectation for one million doses for April has already been downgraded to around 860,000. The overall commitment is for over 80% of the adult population to be vaccinated with at least one dose, by the end of June, and all adults fully vaccinated by September.

The problem of vaccine supplies appears to have largely receded. The next challenge will be the efficient administration of huge volumes of vaccines, through mass vaccination centres, GPs, pharmacists and others. Any failure here and there will be no where for health authorities to hide.

By Friday 26 March, Ireland had received 950,430 vaccine doses. By last Sunday, 806,541 had been administered. Most of the doses Ireland has received have been from Pfizer (654,030), followed by AstraZeneca (228,000) and Moderna (68,400). The Department of Health says that around 95% of available vaccines are administered within seven days of arrival in Ireland. A certain amount must be held back as a buffer for the second doses, up to 50% in the case of Moderna.

It may seem at times that the vaccination delivery numbers change like the Irish weather. What has been forecast, does not always materialise. Minister for Health Stephen Donnelly said that the numbers being promised by pharmaceutical firms can change on a weekly, or even daily basis. For this reason, he said that the Government does not see it as helpful to be publishing forecasts of deliveries, when they know that these can change so quickly. He said it creates anxiety for people.

In the Dáil, Labour Leader, Alan Kelly took the Minister to task about this approach. He told the Minister that transparency was his friend in this issue and that giving out the estimates of vaccines to be delivered is what the Minister should be doing. And the fact that he had come into the Dáil to say he did not want to issue the figures was not acceptable. "You are responsible to Dáil Éireann and to the people of Ireland," he told Minister Donnelly. "and you are refusing to give out the estimates for vaccines for the next three months which the whole country is dependent on."

Vaccination is what now concentrates the mind of the nation. And Europe too. The World Health Organization has said that the vaccination roll-out in Europe has been unacceptably slow. The pressure is on to make better progress in vaccination and to avoid further waves of the virus.

Soon there will be a hub that people will be able to log on to book their vaccination here. The campaign will move to a new phase.

The stakes could not be higher with the national vaccination campaign. There will be no forgiveness for failure. It’s the biggest programme of its kind undertaken by the State. And the whole country is watching every move.