Entirely new COVID-19 variants could emerge this winter but existing vaccines should protect people from serious illness and death, the EU's drug agency said on Friday.

The comments came as the 27-nation EU prepares to roll out a booster campaign ahead of a feared wave of new coronavirus cases later this year.

"There might be a completely new variant emerging that we are not able to predict today," EMA vaccines chief Marco Cavaleri, vaccines chief of the European Medicines Agency (EMA) told a news conference.

On Thursday, the EMA approved vaccines by Pfizer-BioNTech and Moderna that are adapted to tackle the older BA.1 subvariant of Omicron.

A Pfizer version updated for the now-dominant BA.4 and 5 strains should be authorized in mid-September, while a similar Moderna jab is also in the pipeline.

But these new Omicron-adapted jabs will largely be reserved for boosters for the elderly, the vulnerable, pregnant women and healthcare workers, Cavaleri said.

Most people will instead still get the original vaccines that are designed to tackle the original strain of coronavirus.

"The original vaccines are still able to protect against severe COVID-19 disease and death," even if they are less effective at preventing infection.

He said it was "not excluded" that new variants this winter might end up being closer to earlier Omicron strains that had now largely been overtaken by the BA.4 and 5 types.