Stocks of AstraZeneca and Johnson & Johnson vaccines for those under the age of 40 will be limited until at least mid-July, following a Government decision to permit their use in younger age groups.
It is understood the current stockpile of AstraZeneca is reserved for second doses among the over-60s cohort and healthcare workers, a process likely to run until the week beginning July 19th.
There are more, if still limited, supplies of Janssen (Johnson & Johnson) – including about 50,000 currently in pharmacists – with a larger supply anticipated in August.
While the vaccines are currently limited, Professor Brian MacCraith, chair of the High-Level Task Force on Covid-19 Vaccination, told Newstalk Radio on Tuesday that “close to two million doses of AstraZeneca are due to arrive in quarter three”, as well as one million doses of Janssen.
While the National Immunisation Advisory Committee (Niac) has approved the roll-out of the two vaccines among younger people previously considered more suitable for mRNA versions, details of how and when they will be distributed have yet to be worked out.
The Irish Pharmacy Union (IPU) has asked the Government to change rules currently restricting its members to administering vaccines to those aged over 50.
A system to secure qualified consent from younger recipients, confirming they are aware of potential side-effects no matter how rare, must also be finalised, according to a source familiar with the process.
While concern has surround the emergence of unusual blood clots in some AstraZeneca recipients, new research has shown this can be successfully treated where detected early.
Cliona O'Farrelly, professor of comparative immunology at Trinity College Dublin, told RTE the decision to broaden the recipient age profile was "very wise" and that any risk linked to blood clotting were "absolutely infinitesimal" compared to the risk of infection from the delta variant.
Consultant haematologist Dr Michelle Lavin told the broadcaster clotting episodes were about "one in 80,000 vaccinations, so while it is a serious side effect, it is very infrequent".
Niac has also given the go-ahead for the spacing between two AstraZeneca jabs to be further reduced from eight to four weeks, another move intended to expedite inoculation among the over-50s but one that could also complicate availability to younger cohorts.
This decision comes on foot of University of Oxford research on Monday supporting the view that longer durations between the two doses enhanced its efficacy.
However, Sam McConkey, professor of infectious diseases at the Royal College of Surgeons in Ireland, said the real world benefits of getting two jabs as quickly as possible to reduce symptomatic disease outweighed research focusing on the production of antibodies in spaced dose studies.
A supporter of both Government policy moves regarding AstraZeneca, he said it was now imperative to ramp up societal vaccination ahead of an inevitable spike in delta variant infection rates among the younger population.
“Going into a pharmacy and getting a jab of AstraZeneca or even Johnson & Johnson makes sense,” he said. “I would be encouraging young people to get that.”
Prof McConkey also pointed out that despite the previous “super cautious” position of Niac, the European regulator had licenced AstraZeneca for people over the age of 18.
However speaking on Newstalk Breakfast, Liam Fanning, professor of immunovirology at University College Cork, questioned the safety of reducing gaps in the two AstraZeneca jabs, saying the vaccine had been found to have maximum effectiveness with a longer interim period.
Minister for Health Stephen Donnelly has already asked the HSE to put the Niac vaccination recommendations into operation, despite the time it will take for them to materialise.
In a statement on Tuesday evening, the HSE said that just as with previous changes in advice around vaccine administration, it would “take a couple of days to consider it and produce a revised plan quickly”.
“Extensive planning has been required to put in place a programme which will see the remaining approximately 450,000 people in receipt of the AstraZeneca vaccine fully immunised through the administration of a second dose by the week of July 19th next,” it said.