The Health Service Executive (HSE) will be able to reduce the gap between the first and second doses of AstraZeneca vaccine from 12 weeks to eight weeks, under new advice it has received.
The advice is contained in a letter from chief medical officer Dr Tony Holohan to the HSE, written on foot of a fresh recommendation from the National Immunisation Advisory Committee (Niac).
The HSE will now consider the advice and its possible implication in the overall Covid-19 vaccine rollout.
If it reduces the gap, many people who were given a first dose of AstraZeneca will get the second dose at least four weeks earlier.
However, the HSE’s decision will be contingent on there being enough supplies of the vaccine to make this change.
The gaps between AstraZeneca doses was originally 16 weeks but was later reduced to 12 weeks.
UK studies have shown that the AstraZeneca and Pfizer vaccines are only 33 per cent effective in protecting against infection by the delta variant first identified in India, but that effectiveness rises to over 88 per cent after two doses of Pfizer and 60 per cent for Astra Zeneca.
Earlier, Dr Holohan doubled down on his criticism of large crowds socialising in Dublin city centre last weekend.
The scenes of crowds mixing on South William Street “looked like Jones’s Road on the day of an All-Ireland”, he said.
While it could have been anticipated that people would be tempted to come out by the good weather, “if the council had organised an outdoor event they couldn’t have squeezed more people in there”.
Not every outdoors activity is safe, he stressed. “If you get a large crowd in a small area, in close physical contact, that will present opportunities for transmission.”
Meanwhile, people who have had Covid-19 are now presumed to have immunity for nine months, according to Dr Holohan.
This period may be further increased from the previous six-month period to 12 months later this year, he said.
The National Public Health Emergency Team (Nphet) will also look at whether vaccinated people have to wear masks as part of a continuing review over the summer.
A further 407 confirmed cases of Covid-19 were reported by Nphet on Wednesday.
With 5,811 cases reported over the past fortnight, the 14-day incidence now stands at 122 cases per 100,000 people.
Some 81 per cent of cases were among people aged under 45 years, with just 2 per cent in those aged 65 and over.
The median age of cases is 24 years.
Incidence is highest in Limerick, at 376 cases per 100,000 people. The next highest incidence is in Donegal, followed by Offaly and Dublin.
There are currently 93 Covid-19 patients in hospital including 34 in ICU.
The reproduction number, a measure of how many other people a case infects, now stands at “just below 1,” according to Prof Philip Nolan, chair of the Nphet epidemiological modelling advisory group.
Prof Nolan said the situation was stable and the outlook is positive thanks to the effect of vaccination. An average of 11,500 tests a day are being carried out, yielding a positivity rate of 3.7 per cent.
However, unvaccinated people in particular needed to be careful and people generally need to keep their close contacts low over the coming weeks.
Limerick recorded 740 cases in the second half of May, driven by multiple community outbreaks linked to “high risk” indoor activity such as house parties and family events, according to Dr Mai Mannix, public health doctor with the HSE in the mid-west.
The vast majority of cases involved people in their 30s and 40s.
In one instance, 30 cases were recorded in a school after a series of birthday parties and social events involving students. This activity around education led to a “combined pressure cooker effect” in the school, she said.
In a second example, at least 40 cases resulted from a household outbreak which affected all family members. One member attended a social gathering, resulting in four more cases.
Dr Mannix said a family member worked in a place “with strong ties to a particular community” where people tended to gather. From here, the virus spread to three households, another workplace, further households and two education settings.
Dr Mannix said Limerick has recorded more than 50 cases in 20 workplaces during this period, including retailers, beauticians, hair salons, offices and factories. One hair salon had more than 50 contacts.
In some workplaces the wearing of masks appeared to be “intermittent”, she said.
Dr Nolan pointed out that about 70 per cent of the population remains at risk of infection from the virus, but vaccination was cutting this by 5 per cent a week. Arguing against a faster easing of restrictions, he said Nphet was following a “carefully calibrated” process of keeping variants out while people were being vaccinated.
The number of cases of the delta variant first identified in India sequenced in the Republic has increased from 97 last week to 115, according to Dr Cillian de Gascun, director of the National Virus Reference Laboratory.
Dr de Gascun said the data was reassuring but vigilance was still required to ensure no superspreader event occurred.
Three cases of the variant have been identified in mandatory hotel quarantine in the past 10 days, officials said. Most Irish cases have been found in and around Dublin, while a cluster of the related kappa variant has been identified in the south-west.
The delta variant remains “a cloud on the horizon,” according to Dr Holohan.
Northern Ireland recorded no further deaths with Covid-19 on Wednesday, according to the North's Department of Health.
An additional 84 people tested positive for the virus.
A total of 17 patients are receiving hospital treatment for Covid-19 in Northern Ireland, with two in intensive care.
Meanwhile, people aged 40 to 44 years old in the Republic will be able to register for vaccination from Wednesday.
Those in that age group can register online for vaccination at vaccine.hse.ie or by phone at 1850 241850 for appointments. Once successfully registered, the HSE will send the appointment details by text message. People who register will be referred to a HSE vaccination centre and will be vaccinated with the Pfizer or Moderna Covid-19 vaccines.
Minister for Health Stephen Donnelly said that more than half the adult population had received their first dose of the vaccine with more than 2.7 million injections administered.
“We’re moving ever closer to meeting our goal of offering vaccinations to everyone in Ireland who wants one,” he said.
Mr Donnelly said there had been “very encouraging advances technologically” making the Pfizer vaccine much easier to store than the “super-low temperatures” used up to now.
“All of this is going to serve as a backbone for our vaccination strategy for the next two years,” the Minister added.
“We’re also taking steps to plan access to vaccines for countries less fortunate than ours.”
He said that just 2 per cent of cases are now in those over 65 and nearly 80 per cent of cases are those aged 45 or younger.
The reduction of cases for healthcare workers and those in long-term residential care was of the order of 97 per cent or 98 per cent, he added.
Pharmacists will also become involved in the Covid-19 vaccination programme from early June.
Following a long campaign to include pharmacists in the administration of Covid-19 injections, Mr Donnelly said the HSE confirmed on Monday afternoon that they would now have a role.
They would be “particularly important” in “some of the areas which are further from the vaccination centres”.