The spread of Covid-19 remains "stubbornly high" in Dublin despite a big drop in other counties over the past week, chief medical officer Dr Tony Holohan has warned.
There were 321 newly diagnosed cases of the virus in Dublin yesterday and the seven-day average is at between 200 and 300 cases per day.
He also signalled ongoing concern about the number of infections among the over-65s and indicated any easing in lockdown before early December is highly unlikely.
Further doubts were also cast on relaxing advice on the risks of international travel in time for Christmas.
Dr Holohan was speaking as two more Covid-19 related deaths and 767 new cases nationwide were reported yesterday evening.
Speaking about ongoing concerns regarding Dublin he said: "It is a pattern we have seen in other jurisdictions. Dublin is a large city with a concentrated population."
"Dublin was at Level 3 far earlier than the rest of the country and other counties had ground to make up but the virus is not slowing at the rate that would be expected in the capital. The hope is that there will be an improvement this week."
There were 103 Covid-related deaths from the virus in October compared to 36 in September.
Dr Holohan said that despite the overall improvement in the national picture there is still a "long way to go" and the overall daily toll of new cases is still very high.
The fear is that people will drop the high standard of adherence to public health rules as figures improve, he said. "We have to keep going if we want to get the cases numbers we want in early December."
There were 322 Covid-19 patients in hospital yesterday and 44 in intensive care.
Asked about the chances of a relaxation of the advice on international travel in time for Christmas homecomings, Dr Holohan said it will be looked at along with other issues over the coming weeks.
If progress is made and the risk of picking up the virus in this country is reduced then "in relative terms the risk of international travel as a source of infection increases", he added.
The new cases reported yesterday also included 84 in Cork, 47 in Meath, 34 in Limerick, 24 in Roscommon while the remaining 257 were spread across all other counties.
Meanwhile, Dr Siobhán Ní Bhriain of the HSE said that testing and tracing in schools where there is a case of the virus will be speeded up.
Some schools will be "red-flagged" when samples taken from children or staff are sent to a laboratory for processing in order to increase the turnaround time for results.
She also said the HSE had reviewed the role of vitamin D could play in people's fight against Covid-19 .
More advice will be given next week around personal wellbeing in the time of the pandemic.
Around 70pc of people in this country are deficient in vitamin D and there may be a case for people to take a vitamin D supplement, although there is no strong evidence for it as a treatment for Covid-19, she said.
Various studies are under way internationally to see if people who are given vitamin D supplements are at less risk of catching the virus and developing a severe bout of the disease over the winter months.
Meanwhile, cellular (T-cell) immunity against the virus that causes Covid-19 is likely to be present within most adults six months after primary infection, with levels considerably higher in patients with symptoms, a study suggests.
The data offers another piece of the puzzle that could be key to understanding whether previous Covid infections can prevent reinfection, and if so, for how long.
The study, led by the UK coronavirus immunology consortium, is the first to offer data on T-cell levels six months after infection in people with mild or asymptomatic disease that is likely to represent the majority of infections, the authors say.