Chief Medical Officer Tony Holohan has said that there is no certainty that a vaccine for Covid-19 would be produced.
He said that even if a vaccine was developed, issues would remain, including about how long any immunity would last.
Speaking at last night's Department of Health briefing, Dr Holohan said the world was hopeful that a vaccine for Covid-19 could be produced, but that its production could not be regarded as a certainty.
He said that even if a vaccine was produced, it would need to be distributed on a large scale around the world, and that issues would have to be examined including how strong the immunity would be and how long it would last.
Dr Holohan said the World Health Organization had emphasised the importance of countries working together to pool resources and to not leave it to industries to develop vaccines.
He said quick and equitable distribution would also be needed.
Dr Holohan also said that measures aimed at easing the burden of Covid-19 on children were being considered by the National Public Health Emergency Team.
He said the group was engaging with colleagues in the Departments of Education and the Department of Children and Youth Affairs, to see if new measures could be introduced, possibly in phase two of the easing of restrictions.
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The latest figures show that 485 people remain in hospital with confirmed or suspected cases of Covid-19.
This figure is down more than 200 on the same time last week.
Sixty-four of those patients are in intensive care - 49 with confirmed cases of the virus; with 15 suspected cases.
That compares to 56 confirmed cases in ICU last week, and 17 suspected cases.
The number of available beds has fallen, however as the number of non Covid-19 patients increases.
There are 991 general beds available in the country's 29 acute hospitals at the moment, compared to 1,137 a week ago.
There are also only 107 intensive care beds available, down from 155 last Saturday.
Separately, the number of people who have died after testing positive for the coronavirus in Northern Ireland has risen to 505, after one more death was reported by the Department of Health there.
The department also reported a further 41 cases of confirmed Covid-19, bringing the total number of positive cases in Northern Ireland to 4,545.
Around 80% of cases of Covid-19 will be a mild to moderate illness, close to 14% have severe disease and around 6% are critical.
Generally, you need to be 15 minutes or more in the vicinity of an infected person and within 2 metres of them, to be considered at-risk, or a close contact.
Additional reporting Orla O'Donnell, PA