It is “well worth considering” changing the vaccine rollout plan to get as many first doses out as possible before moving on to second doses, according to Professor Luke O’Neill.

On The Pat Kenny Show this morning, the Trinity College immunologist noted that all three currently available vaccines are highly effective after a single shot.

“If the single shot is really efficacious, why wouldn’t you give it to as many as people as possible?” he said. “Because it will, first of all, protect them anyway and secondly, slow transmission.

"As we know now, the Pfizer vaccine is working and so is Moderna - there is more and more evidence that the vaccines are stopping transmission - so, if the single shot gives you a reasonable level of protection and a reasonable level of decreased transmission, why not use it up on as many people as possible in a population if, in that population, you will have a big effect?”

Single-shot

He noted that the single-shot Jansen vaccine, due to arrive in Ireland later this month, is no more effective than a single shot of the three we already have.

“Pfizer gave a 92.1% efficacy from a single shot, Moderna was 92.6%, AstraZeneca was 76% - that is a single shot,” he said.

“These are as good as Johnson and Johnson, by the way - which has been approved as a single shot anyway.

“So now there is talk of just get that supply out. Don’t be keeping some back; get as many people as you can vaccinated quickly because it will have an impact then on the level of illness and transmission.”

Vaccine

The Trinity professor noted that the UK, where 31.6 million people have had their first dose but only 5.5 million have had their second, is essentially already following a single dose policy.

“We don’t know yet if you need a second shot for a durable response that might go on for a year or two, but certainly, in this emergency, some people are saying it makes sense to get that first shot out as quickly as possible and I think it is well worth considering,” he said.

Professor O’Neill said there is now “lots off debate” about focusing on single-shot administration, “especially in the developing world where there won’t be sufficient supply.”

“They have only got about two billion doses guaranteed there, which is only 25% coverage if you use two shots so again, they are probably going to press for single shots for all the vaccines in the developing world,” he said. “I bet that is what is going to happen.”

Variants

He said a single-shot rollout could also reduce the risk of new variants emerging.

“The big question as well is these variants because if they are emerging in the developing world you want to get as many people covered with a single shot as quickly as you can to stop more variants cropping up which could be an issue,” he said.

“So again, that might just decide the use of a single shot more widely to limit the chance of those variants emerging.”

Later in the show, the Health Minister Stephen Donnelly said a single-jab approach was not being looked at – suggesting, “it's not something we need to consider.”

"It's not something we're discussing for Ireland - the two jabs do provide that very, very strong effectiveness and we will have enough vaccine,” he said.

You can listen back to Professor O'Neill here: