U.S. stock dropped on Friday on renewed Covid fears over a new variant found in South Africa.

The Dow Jones Industrial Average dropped 800 points, or more than 2%, while the S&P 500 and Nasdaq Composite slid 1.4% and 0.9%, respectively. Friday is a shortened trading day because of the Thanksgiving holiday with U.S. markets closing at 1 p.m. ET.

The downward moves came after WHO officials on Thursday warned of a new Covid-19 variant that’s been detected in South Africa. The new variant contains more mutations to the spike protein, the component of the virus that binds to cells, than the highly contagious Delta variant. Because of these mutations, scientists fear it could have increased resistance to vaccines, though WHO said further investigation is needed.

The United Kingdom temporarily suspended flights from six African countries due to the variant. Israel barred travel to several nations after reporting one case in a traveler. Two cases were identified in Hong Kong. Belgium also confirmed a case.

“When I read that there’s one [case] in Belgium and one in Botswana, we’re going to wake up next week and find one in this country. And I’m not going to recommend anyone buy anything today until we’re sure that isn’t going to happen, and I can’t be sure that it won’t,” CNBC’s Jim Cramer said.

Bond prices rose and yields tumbled amid a flight to safety. The yield on the benchmark U.S. 10-year Treasury note fell 12 basis points to 1.52% (1 basis point equals 0.01%). This was a sharp reversal as yields jumped earlier in the week to above 1.68% at one point. Bond yields move inversely to prices.

Oil prices also tumbled, with U.S. crude futures down 6.2% to $73.57 per barrel, while the South African rand weakened 1.7% against the greenback to 16.231 per dollar.

Asia markets were hit hard in Friday trade, with Japan’s Nikkei 225 and Hong Kong’s Hang Seng index both falling more than 2% each. Bitcoin fell 8%.

The Cboe Volatility Index, often referred to as Wall Street’s “fear gauge,” rose to 28, its highest level in two months.

Travel-related stocks were hit hardest with Carnival Corp. and Royal Caribbean down more than 10% apiece in early trading. United Airlines dropped 9%, Delta Air Lines and American Airlines were each down more than 7%. Boeing lost 6%. Marriott International fell more than 7%.

Bank shares retreated on fears of the slowdown in economic activity and the retreat in rates. Bank of America and Citigroup were each down more than 4%.

Industrials linked to the global economy declined led by Caterpillar off by 3.7%. Dow Inc. shed 3%.

Chevron dropped 3.2% as energy stocks reacted to the rollover in crude prices.

On the flip side, investors huddled into the vaccine makers. Moderna shares gained more than 16%. Pfizer shares added 5%.

Some of the stay-at-home plays that gained in the earlier months of the pandemic were higher again. Zoom Video added nearly 9%. Netflix was up 1.5%.

“It’s important to stress that very little is known at this point about this latest strain, including whether it can evade vaccines or how severe it is relative to other mutations. Therefore, it’s hard to make any informed investment decisions at this point,” Bespoke Investment Group’s Paul Hickey said in a note to clients. “Historically speaking, chasing a rally or selling into a sharp decline (especially on a very illiquid trading day) rarely ends up being profitable, but that isn’t stopping a lot of people this morning.”

Several investment professionals told CNBC on Friday that the sell-off could be a buying opportunity.

“Friday is the day after Thanksgiving, probably not as many traders on the desks with an early close today. So potentially lower liquidity is causing some of the pullback,” Ajene Oden of BNY Mellon Investor Solutions said on CNBC’s “Squawk Box.” “But the reaction we’re seeing is a buying opportunity for investors. We have to think long-term.”

Markets were closed on Thursday for Thanksgiving, so stocks are coming off of slight gains on Wednesday that staunched the week’s losses for the S&P 500 and Nasdaq Composite. Trading volume tends to be light during holiday weeks.

A move higher in Treasury yields earlier this week put pressure on high-growth stocks. The Nasdaq is down 1.3% for the week, while the S&P 500 is up less than 0.1% and the Dow has gained roughly 0.6%.

The final weeks of the year are typically a strong period for the market, with the so-called Santa Claus rally usually creating a happy holidays for Wall Street. The S&P 500 is up 25% year to date.

Friday also marks the unofficial start of the holiday shopping season, as investors will be looking for insight from Black Friday to determine the mood of the U.S. consumer.

Retail executives spoke in recent weeks about how they are managing supply chain issues and inflation. It also remains to be seen if discussion around supply chain issues caused consumers to start their holiday shopping early, potentially denting fourth-quarter sales.

“I would not be surprised if that was a dynamic around the holiday season,” said Sarah Henry, a portfolio manager at Logan Capital Management. She added that her firm was looking for companies with long-term strategic advantages than trying to bet on the best holiday sales results.

Wednesday also saw several strong economic reports, with personal incomes and consumer spending for October coming in higher than expected and initial jobless claims hitting their lowest level since 1969. However, Core PCE, the Fed’s preferred inflation gauge, remained elevated at 4.1%.

There are no major economic releases scheduled for Friday.