Europe's major stock markets sank at the open on Thursday as investors fretted that surging global coronavirus infection and death rates could damage economic recovery from the pandemic.
Massive gains earlier in the week driven by news of successful vaccine trials gave way in the face of the rising numbers, dealers said.
In initial deals, London's benchmark FTSE 100 index of big blue-chip companies slid almost 0.9% to 6 327.60 points as traders shrugged off rebounding third-quarter UK economic growth.
In the eurozone, Frankfurt's DAX 30 also dropped 0.9% to 13 091.86 points and the Paris CAC 40 lost 0.6% to 5 411.66.
Markets faltered after a rally spurred by Joe Biden's election win over Donald Trump and US pharma giant Pfizer's announcement that its vaccine candidate had proved to be 90 percent effective.
A worrying spike in new infections in the US and Europe has fanned concerns about a deadly winter in the northern hemisphere with several countries already in lockdown.
"European bourses are heading lower... as vaccine optimism, which has driven the rally across the first part of the week, fizzles and the Covid-19 trade is back in play," said City Index analyst Fiona Cincotta.
"In Europe, Covid-19 figures continue to deteriorate pointing to a very challenging winter before any vaccine will be widely available.
"The UK reached a grim milestone of 50 000 Covid-19 deaths, whilst Italy hit one million cases, the third country in Europe to pass the milestone after France and Spain."