Dr Colm Henry has said that "for a second time," Ireland has managed to turn the tide against the coronavirus.
The HSE's Chief Clinical Officer said that the positive news was perhaps due to Ireland "learning from mainland Europe" and implementing restrictions early.
However, Dr Henry explained that the main reason was the effort and sacrifices that the Irish public have made over the last few weeks.
During an interview on RTE, he said: "It is most of all due to the collective effect of the individual efforts of every single Irish person. We have managed to turn that tide again and to flatten that curve.
"We're seeing falling numbers of cases, a falling 14-day incidence, a falling 7-day incidence as a proportion of the 14-day in every county, bar four and a falling number of tests requested.
"This all points to us having grappled with the virus and gotten it under control a second time.
"The 14-day incidence of the disease is now down by 51% compared to the previous two weeks."
He added: "It's important to recognise an interim report on a phase three trial is but one more step closer to widespread immunity in the population which we need to achieve.
"We need to achieve 60%-80% immunity in the population for a vaccine to be effective.
"In the meantime, we need to keep our eye on the ball and stick to those social-distancing measures, mask-wearing, and washing hands."
Earlier in the interview, Dr Henry denied any reports that 600,000 doses of the flu vaccine went missing.
He said 50,000 doses were deliberately held back to ensure they are delivered to those groups who need it the most.
Dr Henry noted that the Covid-19 pandemic has resulted in unprecedented levels of demand for the flu vaccine this year with 1.3 million doses already distributed.
The HSE deliberately made the decision to hold back a certain amount of the doses to ascertain where the gaps and priority areas around the country are and where the vaccine needs to be delivered to.
