The vaccination roll-out has become an uneven race for many people who are vulnerable to Covid-19.
his month, people aged in their 50s who got the Pfizer or Moderna vaccines in May will get their second dose and be fully vaccinated.
But the gap between doses is at least eight weeks for most of those aged in their 60s who received a first dose of the AstraZeneca jab. This also applies to a significant number of people with underlying illnesses.
Younger groups who are at less risk will have earlier protection against the Delta variant of the virus than those more susceptible through age.
So what does it mean for people as the country opens up?
Figures from the HSE last week showed that a higher percentage of people in their 50s have had two doses of vaccine than those in their 60s. Overall 80pc of people in their 50s had got a jab, with 10pc fully vaccinated. This compared to 90pc of those in the 60s but just 8pc had two jabs at that point.
Casting a shadow
The Delta variant of the virus, which was first seen in India, has been described as the black cloud hanging over how quick restrictions can be eased. The aim is to get as many people as possible fully vaccinated here before it gains significant ground. It is more infectious and the evidence is that having just one dose of vaccine provides substantially less protection than if a person has two doses.
There is evidence from laboratory investigations and real-world data that the current vaccines are less effective against the Delta variant.
Public Health England analysis found after just one dose of the Pfizer or AstraZeneca vaccines, there was a 17pc absolute reduction in effectiveness against symptomatic Covid-19 disease with the Delta variant compared to the UK, or Alpha, variant which is dominant there.
The clear message is that the best protection against this variant is to have two doses.
We do not know what impact the reduction would have on how sick someone would become.
There is still no data on how the one-shot Johnson and Johnson vaccine responds to the Delta variant.
Shortening the gap
The HSE has accepted a recent recommendation from the National Immunisation Advisory Committee (Niac) to try to shorten the gap between the first and second doses of AstraZeneca. It should reduce from 12 weeks to eight weeks.
However, because of uncertainty over supplies it is having to be phased in.
Over this week and next, people who were already due their vaccine as part of a 12-week schedule will get a second dose.
Then there will be a graduated reduction so the interval will reduce to 11, 10, nine and then eight weeks. Much will depend on the timing and volume of deliveries.
It has been suggested that one way of meeting the eight-week timeline is to give people who had a first dose of AstraZeneca vaccine a second dose of Pfizer or Moderna vaccines.
As yet there has been no recommendation to do this, although it has been adopted in five countries. The European Medicines Agency said that while studies around this are under way, the evidence so far is that it is safe.
In the queue
Around 400,000 people are eligible for an earlier second dose of AstraZeneca vaccine.
People with underlying conditions, those in their 60s, and healthcare workers are at various stages between their first and second dose of the vaccine. There was no choice of vaccine and that was understandable given the problems with supply .
For those in their 60s, the choice was to take the AstraZeneca vaccine or go to the back of the queue. This was due to the decision to restrict it to older age groups after it was found there was a very small risk of unusual blood clots after getting the jab.
We are still learning more about the Delta variant. Around 126 cases have been detected here. In the Britain, it is casting a shadow over the next phase out of lockdown there on June 21.
It is possibly 40pc more transmissible than the Alpha variant. Research also suggests it is associated with a more than twofold higher risk of hospitalisation, although more work needs to be done to confirm this. A report from the Health Protection Surveillance Centre on the first 144 cases of the Delta virus detected here shows there were 13 cases in children under 18 and one in a person over 65. The highest number of 67 was in people aged 19-34, followed by 22 among 35 to 44-year-olds. Another 11 cases were found in people aged 45 to 64.
So far around 55pc of the population here has at least one dose and 26pc are fully vaccinated.
Around 280,000 doses will be administered this week.