European equities fell in opening deals on Tuesday after the head of Moderna warned current coronavirus vaccines might be less effective at fending off the Omicron variant.
In initial trade, London's benchmark FTSE 100 index reversed 0.9 percent to 7,047.14 points.
In the eurozone, Frankfurt's DAX shed 0.9 percent to 15,137.86 points and the Paris CAC 40 lost 1.1 percent to 6,702.83.
Asian bourses and oil prices also took a tumble following the remarks.
Moderna chief executive Stephane Bancel's comments, in an interview with the Financial Times, sent traders running for cover.
"There is no world, I think, where (the effectiveness) is the same level . . . we had with Delta," he told the daily business newspaper.
The high amount of mutations on Omicron and its swift spread in South Africa indicated the present jabs would need to be tweaked, he indicated.
"Bancel ... predicted existing vaccines would struggle with the Omicron variant," said CMC Markets analyst Michael Hewson.
The Moderna chief "warned it would take months for pharmaceutical companies to manufacture enough jabs at a sufficient scale to make a difference", Hewson added.
"His tone contrasts with the likes of Pfizer and BioNTech was suggested any new vaccine would be able to modified fairly quickly."