'Completely new' Covid strains possible this winter: EU
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The comments came as the 27-nation European Union prepares to roll out a booster campaign ahead of a feared wave of new coronavirus cases later this year.
It will include a mix of newly-approved jabs adapted for the now dominant Omicron strain, and the original vaccines developed to fight the virus that first emerged in China in 2019, the European Medicines Agency (EMA) said.
But people "should not wait for a specific vaccine", EMA vaccines chief Marco Cavaleri told a news conference.
"There might be a completely new variant emerging that we are not able to predict today."
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 authorised 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 Wuhan 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.