Ireland and other EU countries have been warned they cannot "booster" their way through the pandemic with another vaccine every three to four months as we risk overloading the immune system.
The warning came from a top official Marco Cavaleri, head of vaccine strategy in the European Medicines Agency (EMA), which Ireland and the rest of Europe relies on for a green light on vaccines and other Covid-19 medicines.
He expressed doubts about the need for a fourth booster dose of Covid-19 vaccine and said there is currently no data to support this approach as it seeks more data on the fast-spreading Omicron variant.
He raised concerns that a strategy of giving boosters every four months hypothetically poses the risk of overloading people's immune systems and leading to fatigue in the population.
He also said that more data on the impact of the new Omicron variant on vaccines and a better understanding of the evolution of the current wave was needed to decide whether an Omicron-specific vaccine was needed.
Around 500,000 people in Ireland were infected with Omicron last week as it raced through the population.
Pfizer said it could have a new vaccine targeting Omicron ready by March.
But it needs to be approved by the EMA and Mr Cavaleri indicated it would take until April at least before this will be possible.
It means that Ireland will be reliant on existing vaccines until early summer.
He said: "It is important that there is a good discussion around the choice of the composition of the vaccine to make sure that we have a strategy that is not just reactive...and try to come up with an approach that will be suitable in order to prevent a future variant."
The EMA said it was currently in conversation with vaccine developers in case there is a need for an updated vaccine, but added that any such change would need to be coordinated globally.
Over 60pc of people here who are eligible for a booster have got the jab but the great rush of enthusiasm which saw people in a queue for hours outside HSE vaccination centres had died down.
Although there have been calls for Ireland to follow the lead of Israel and give people another booster dose the EMA said it has still not seen data to support this.
Mr Cavaleri said he was "concerned about repeated vaccination within a short term".
He said we cannot jab people every three to four months, although this may be possible for people who are immunocompromised.
He hoped that the Omicron variant would create a lot of natural immunity due to the numbers infected.
The most likely scenario is that people will get a Covid-19 shot before every winter in the same way they get the flu vaccine.
A new variant will emerge but we need to come up with a strategy to fight it, added Mr Cavaleri.