The virus “still retains a very strong disruptive capacity, which I think has been underestimated by people,” Micheál Martin said, referring to both the hard-hit health system and wider economy.
Mr Martin said rollout of the fourth round of Covid vaccines is likely in the autumn due to an “evolution of the virus”.
New injections could incorporate the latest variants, Mr Martin added, amid a summer spike in infections. This current wave has increased pressure on hospitals and seen dozens of flight cancellations as airlines grapple with staff Covid absences.
Mr Martin’s comments come as Dr Cillian de Gascun, director of the National Virus Reference Laboratory, said yesterday it could be presumed there will be an increase in cases this winter, with those who had Covid at the beginning of the year left with no immunity.
Mr De Gascun said vaccine manufacturers were looking at incorporating the latest strains into a new jab that would also protect against an expected flu outbreak.
The Taoiseach said he was “worried” about the coming winter, but a new vaccination programme for all would depend on the advice of the National Immunisation Advisory Council (Niac).
Mr Martin also expressed confidence that any new programme of jabs can be rolled out efficiently, despite the loss of so many senior health personnel from public health officials Dr Tony Holohan and Dr Ronan Glynn, to departing HSE boss Paul Reid.
“We’re still concerned about the fact that quite a substantial number of people who should have had a second booster – a fourth dose in total – haven’t actually gone to get that booster,” Mr Martin said.
“I do believe that in the autumn there will be further advice coming from Niac in respect of others, younger age cohorts perhaps, and they would be advised to get a booster,” he said.
“I would urge those who have been advised by Niac to get the fourth vaccine to take it,” he said, noting that the American health authority, the FDA, has recommended that vaccines would be reconfigured to take on board the Omicron sub-variants.
“That could be a signal in terms of what might happen in the autumn in respect of vaccines,” the Taoiseach said.
“We’re going through different phases and we’re going through an evolution in terms of this virus.
“What’s clear is that it still retains a very strong disruptive capacity, which I think has been underestimated by people.
“A lot of the pressures in hospitals is the hangover from Covid. And the fact that it’s now gone into another summer wave means that there is a significant disruption in our hospitals because of isolation protocols, and the pressure on hospital staff.
“Likewise, across the economy also,” Mr Martin said, referring to flight cancellations last week and a slowdown to a range of services, including in the private sector, because of staff shortages as a result of illness.
“We are worried about the winter period in particular,” he said, admitting this was why legislation was introduced last week to allow for new mask-wearing mandates across society.
“We’re taking contingency measures,” he said.
“I don’t want to find ourselves in a position in the autumn where we might have to respond with masks. Hopefully we don’t and we may not have to go there at all, but we should always be prepared.”
Mr Martin said he did not want to anticipate or pre-empt a new national programme of a fourth jab.
“At the moment, it’s recommended for those who are immunosuppressed and for the over-65s. That may come down. But that’s a matter for Niac, particularly in respect to the winter period.
“What is very clear, though, is that the primary doses have given people a lot of protection against severe illness and death. That’s very reassuring.
“So the vaccines have worked and they’ve turned out to be the big game-changer. So we will continue to listen to the science.”
Mr Martin said he believed the departure of “very significant personalities” from the health service reflected the enormous pressure that people were under during the pandemic.
“This was 24/7 in the public spotlight, in an unprecedented situation, a once-in-a-century pandemic, and all of them give selflessly of their time and on top of normal work.
This, he believed, formed “an element” of their departure decisions. “There’s no doubt about that. Right across the public service, civil servants, the senior echelons, gave it everything during Covid.”
The HSE cyber attack had also caused nightmares, he said.
"That was an enormously stressful period for everybody in the health service. So I think that’s a part of what we’re seeing.
“But we have strong resources within the HSE and within the health community in general.
“A lot of people will now come forward to take up those leadership positions.”