Over 20,000 children aged between 12 and 15 have received a COVID-19 vaccine so far.
Registration opened for teenagers on Wednesday evening to get a Pfizer or Moderna jab.
More than 80,000 have registered already, and a quarter of them have already received their first dose.
More than 6.3 million doses have now been administered, with 90% of adults having received at least one dose and 81% now fully vaccinated.
HSE CEO Paul Reid says Ireland's now likely to focus on the two mRNA vaccines for future vaccine needs.
He said: "At the EU-level, the steering board has recommended each country make a decision to suspend the further delivery of Johnson & Johnson and indeed AstraZeneca.
"That’s the approach we’ll likely be taking."
He said the rising number of cases - including more than 2,000 yesterday, for the first time since January - is a cause for concern, and that many of the 248 people currently in hospital with the virus are very sick.
However, he said people should take "stronger encouragement" that the vaccines are working to prevent more people from being admitted to hospital or ICU.
