How far Covid-19 booster vaccines should be extended is the next big question facing us in the coming months.
uch will depend on the real-world data that is coming back about how full dose vaccination is holding up in protecting people from infection, illness, hospitalisation and death.
Some countries are already well ahead, with Israel banning anyone without a Covid-19 booster jab from entering indoor venues.
So what do we know about vaccine effectiveness so far?
Around 5.7m doses of the Pfizer/BioNTech vaccine have been administered here. It has been the workhorse of the roll-out, with more people getting this vaccine than any of the other three.
The Lancet medical journal this week provided an insight into how people who have had two doses are progressing. It found that vaccine effectiveness in reducing a person’s risk of hospitalisation for all variants, including Delta, remains high at 90pc for at least six months. But its protection waned – down to 88pc in the first month and 47pc after six months.
Data published by Public Health England found that in over-65s, protection from symptomatic Covid-19 stood at 55pc after five months.
Around 1.9m doses of AstraZeneca vaccine have been administered here.
It is no longer routinely used and was mainly given to healthcare workers, people who were immunocompromised and the 60-69 year age group.
A recent study from Public Health England found that among people over 65 , who were not in a clinical risk group, protection against hospitalisation was under 80pc with AstraZeneca. This was more than five months after the second dose.
In the over-65s, it had 36pc efficacy against symptomatic Covid-19 disease with the Delta variant. There is a strong likelihood that 60 to 69-year-olds will be offered a booster of Pfizer or Moderna vaccine.
Last month, the Centre for Disease Control (CDC) in the United States said Moderna vaccine was 92pc effective in preventing hospitalisations after four months. Roughly 569,900 doses of the vaccine have been administered here.
Johnson & Johnson vaccine
The one-jab Johnson & Johnson vaccine has been given to 235,587 people here. The CCD found it was 71pc effective in preventing hospitalisations when studied between March and August last. A study of half a million health workers in South Africa found that it cut the risk of getting infected with the virus by about half.
Additional vaccines and boosters
It is difficult to draw definitive conclusions about effectiveness of vaccines in those who are fully jabbed with any of the four vaccines administered here because of so many different elements at play.
There is no standard methodology among the studies, which are individual snapshots. There are other variables to be taken into account such as age and underlying condition.
So far, people with very low immune systems, the over-80s and people aged over 65 in nursing homes are being offered an extra shot of Pfizer or Moderna vaccine.
Future booster shots would likely involve either of these jabs.
Visit our Covid-19 vaccine dashboard for updates on the roll out of the vaccination program and the rate of Coronavirus cases Ireland