While crude prices have undulated with the dollar and broader risk assets in recent days, it’s also being supported by renewed strength in the market’s structure.

U.S. crude’s closest contract is near the most expensive versus those for six months out in more than a year. It’s a similar picture for Brent. The structure, known as backwardation, indicates tight supply. The International Energy Agency this week said it expects inventories to fall by 100 million barrels this quarter, despite a surge in Covid-19 outbreaks.

Traders have piled into oil this year, with output cuts from Saudi Arabia helping drive prices to the highest since February. Virus vaccines have boosted oil demand and the global economy, and U.S. Treasury Secretary nominee Janet Yellen on Tuesday called on lawmakers to “act big” on stimulus. Still, the pandemic continues to be a risk with China locking down part of Beijing in the worst outbreak in months and Europe also reeling.

“As long as investors believe vaccinations will bring back normal life at some stage later this year every setback is used to buy into the market,” said Giovanni Staunovo, an analyst at UBS Group AG.

Chinese imports of U.S. and Russian crude last month were at similar levels to November, while purchases from Saudi Arabia and Iraq fell, according to customs data released Wednesday. Imports from Iran almost doubled.