An immunologist says the evidence is "very clear" Ireland will need a booster campaign through the autumn.
NIAC will decide next week if a campaign is needed as the country heads into the winter and flu season.
Yesterday the committee recommended the mixing of vaccines in some situations, like when someone is seriously concerned about getting the same jab twice.
Professor Christine Loscher says international studies are showing boosters will be needed.
"There is a small waning of immunity, which you would see normally with the vaccine over time.
"I think the difference in this situation is that because of the threat of Delta and because it's so highly transmissible, even a small decrease in immunity can potentially have a large impact.
"I think for that reason we need to prioritise boosters for our older cohorts and our more vulnerable cohorts."
Meanwhile the number of daily covid admissions to intensive care has double in the past week.
The figure has increased from 3 to 6 since last Tuesday, according to the Chief Medical Officer.
Dr. Tony Holohan's also warning the incidence of the disease is now at its highest level nationally since January.
Meanwhile there are 230 covid patients in hospital and 54 in ICU.
