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The month of October and the fourth quarter was off to a strong start Friday after the third quarter was the worst for the stock market since the start of the health crisis.

The Dow surged 482 points. The S&P 500 rose 49. The Nasdaq gained 118.

But it still was a down week. The S&P 500 shed more than two percent in its biggest weekly drop since February.

Investors are keeping their eyes on the deliberations in Washington, which will have the potential to quickly swing markets, says Winthrop Capital Management Portfolio Manager Adam Coons.

"What we'll see is just a range bound market for a little while while we just kind of process through this. Obviously, the things going on in D.C. play a part in that. So what we'll see is big up days, big down days. But ultimately we think we just trade flat for a while."

Merck helped set an overly positive tone for the day. The drugmaker said its experimental oral antiviral COVID-19 medication reduces the chance of hospitalization or death for patients at risk of severe disease by around 50 percent. It plans to seek emergency authorization for use in the U.S. and apply for regulatory approval in other countries.

Shares of Merck hit a multi-year high...up more than 8 percent on the day.

The trial results fueled hopes that Americans will feel confident enough to go out and be sociable. Airlines, hotels, cruise ship operators, retailers, and restaurant chains all saw their stocks move higher.

But on the flip side - investors fear vaccine makers like Moderna could sell fewer doses. Shares of Moderna got slammed - down some 11 percent. Shares of BioNTech were down nearly 7 percent. Pfizer, which is working on an oral COVID-19 treatment, saw much smaller losses.

Economic data kept the positive vibes flowing. Consumer spending rebounded sharply in August - up 0.8 percent.

And though a measure of inflation remained hot it didn't get much hotter. The core personal consumption expenditures index, a measure favored by the Federal Reserve, rose 3.6 percent on an annual basis - matching the jump seen through July.

In a separate report, manufacturing activity was stronger in September but persistent supply chain disruptions are keeping prices high.