Immunologists and doctors say they are hopeful the Johnson & Johnson Covid-19 vaccine will be approved for use in Ireland across a broad range of age groups.

The National Immunisation Advisory Committee is continuing to consider what recommendation it will make on the single dose jab.

The roll-out of the vaccine was paused in the European Union and the United States due to rare cases of unusual blood clots among six out of 6.8 million people in the US who had received the vaccine.

Earlier this week, a safety review by the European Medicines Agency found that while there is a possible link with blood clotting events, the benefits of the Johnson & Johnson jab - marketed as Janssen in the EU - outweigh the risks.

And last night, health authorities in the US recommended that the pause be lifted and that vaccine can be used in people aged 18 years and over.

An announcement on the use of Johnson & Johnson here is expected from NIAC in the coming week.

Kingston Mills, Professor of Experimental Immunology at Trinity College Dublin, today said he would be "hopeful" that NIAC will make the vaccine available to all age groups.

He said: "I think there is no reason why this vaccine shouldn't be used across all age groups" adding that "restricting it to older age groups would not be the right decision".

Prof Mills commented: "I think it would be better if they could use this vaccine particularly for people in high-risk settings, people who are more likely to be in areas of high virus transmission regardless of their age."

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He said confining the vaccine to people aged over 60, as was recommended for the AstraZeneca vaccine, would "be a shame because the risks are so small and the EMA has said the benefits outweigh any risks".

Dr Austin O'Carroll, the HSE Clinical Lead for the Covid Homeless Response, said the single dose jab "has some excellent benefits" and would be extremely useful in vulnerable groups.

"Firstly it's one shot. So for homeless people, who are very mobile, we don't have to chase them down for the second shot.

"And the second big benefit is it is transportable. We can bring it to the hostels because a lot of people may not come to a centre for vaccination and this gives us a lot more flexibility in the delivery."

Dr O'Carroll said he will trust NIAC in whatever decision is made but said he is "very hopeful" that it will approve the jab "because the EMA have [already] approved it for use".

He added: "The rates of clots are extremely low and the protection it offers is extremely huge, so I would be very hopeful that NIAC will approve it across a broader age range than AstraZeneca."

Dr O'Carroll described it as "a game-changer vaccine" because using it means "you can rapidly increase the uptake both for vulnerable but also the general population".

As of 22 April, 1,317,165 doses of Covid vaccines had been administered in Ireland and of these, 934,980 were first doses and 382,185 were second jabs.