The Professor of Biochemistry at Trinity College Dublin said booster shots in the autumn will “really kick off the immune system to protect against multiple variants”.
“The way out of this variant issue is extensive vaccination now of course, but then also booster shots with any of the vaccines,” he said.
Professor O'Neill had been asked by a listener to the Pat Kenny Show if the Johnson & Johnson one-shot vaccine was effective against the Delta variant.
“There’s evidence in the lab,” he said. “They’ve taken blood from people who had Johnson & Johnson and then tested the antibodies. It is able to neutralise Delta.
“It is lessened - all the vaccines are slightly weakened in that regard. But still, Johnson & Johnson is driving an immune response in people that should protect against Delta.”
However, Professor O’Neill noted that as the Johnson & Johnson jab has not been as widely used in the UK where the Delta variant has spread rapidly, there is no significant field data available yet.
But he insisted that scientists are “confident” it does protect people from severe disease.
“That’s the key metric - it doesn’t matter if you get infected really, as long as it doesn’t progress into severe disease,” he added.
“The only way to handle these variants is booster shots in the autumn - that will really kick off the immune system to protect against multiple variants.
“The way out of this variant issue is extensive vaccination now of course, but then also booster shots with any of the vaccines.”
It was revealed earlier this week that a vaccine booster campaign against Covid-19 is being planned for the winter with health officials giving people top-up jabs using single-dose Pfizer shots.
The National Immunisation Advisory Committee (NIAC) will use available immunity data to decide when the revaccination campaign will begin.
It is believed most mass vaccination centres will begin to close in the autumn, and the rollout will move to pharmacies and GPs.
Professor O'Neill also said it was “tremendous" that antigen testing will be used for large events.
Speaking in relation to Government confirmation that rapid antigen testing will be used for Ireland's first music festival since the pandemic began, at Royal Hospital Kilmainham on July 3, Professor O’Neill said “this is exactly what we want to see”.
“Any big event should really have antigen testing at it, and that’s going to happen. It’s a really good development.”
He added: “We're going to see a lot more" rapid testing at such events, and we now "just need to get on with it.
“It’s all the more relevant with the Delta variants," he added. "The antigen tests do pick up that variant - now we know that’s spreading in younger people, you can catch it through antigen testing."