Oil prices have slipped due to concerns regarding oversupply in the market and uncertainty about a vaccine to end the novel coronavirus (Covid-19) pandemic.

Brent crude futures decreased by $0.31 to reach $47.49 a barrel by 7:58am GMT while US West Texas Intermediate (WTI) futures dropped by $1.02 to touch $44.69, Reuters reported.

Both the Brent and the WTI benchmarks rose 6% this week after British drug-making firm AstraZeneca said that its vaccine could be more than 90% effective.

The company’s drug candidate adds to the successful trial results of two others currently under development.

However, several scientists expressed doubts regarding how strong the results of the clinical trials were.

OANDA senior market analyst Jeffrey Halley was quoted by the news agency as stating: “With much of oil’s rally in November built on expectation, sentiment and speculative fast money, some sort of correction was long overdue.

“A thin market and the OPEC+ ministers meeting on Monday seem to have been the precursors for traders to lighten bullish positioning.”

Three sources close to OPEC+ said that the Organization of the Petroleum Exporting Countries (OPEC), and allies, including Russia, together known as OPEC+, are planning to postpone a planned increase in supply.

OPEC+ will discuss its ‘output policy’ during the ministers meet on 30 November and 1 December.

Libya’s rising output is contributing to fears regarding oversupply as many people are not following lockdown measures.

The US Transportation Security Administration said that six million Americans took air trips between 20 and 25 November in advance of the Thanksgiving holiday, ignoring advice from the Centers for Disease Control to stay home and be safe.