New coronavirus infections in the U.S and elsewhere are at record levels.
And tightening restrictions have dampened hopes for a near-term recovery in the global economy.
That played into oil markets again on Friday (November 13).
Brent crude fell as much as 1.2 percent in early trade, continuing declines on Thursday (November 12).
U.S. West Texas Intermediate crude futures fell as much as 1.6%.
But for the week, both were headed for a surge of about 9%, helped by hopes for a vaccine.
The International Energy Agency though remained cautious.
It said on Thursday that global oil demand is unlikely to get a significant boost from any roll-out of vaccines until well into 2021.
One analyst told Reuters that oil prices will continue to stay under pressure "if the spread of the pandemic continues to accelerate".
Also on Friday, the fallout from the pandemic and a weaker rouble sent Russian energy giant Rosneft to a third-quarter net loss of $827 million.
Rosneft is the world's second-largest oil producer by output behind Saudi Aramco.
It was forced to reduce oil production in line with a move by OPEC and allies to stabilise global markets.