The Dow closed up 2.9%, or 835 points, after Pfizer announced promising, though early, findings about the effectiveness of its coronavirus vaccine. The S&P 500 finished up 1.2%.The state of play: The vaccine progress is fueling market optimism about a possible return to normal, as the coronavirus pandemic and social-distancing restrictions have held back the U.S. economy.By the numbers: The stock market closed at the lowest levels of the day. At one point, the Dow was up more than 5%, while the S&P soared over 3%.The tech-heavy Nasdaq closed down 1.5%, as technology stocks sold off.The Russell 2000, a stock market index that measures America's smallest public companies, jumped 4.3% and closed at its highest level in two years.Between the lines: Companies that benefited from the stay-at-home economy — largely those in the tech sector — saw their share prices sink.Shares of video-conferencing software company Zoom closed down 17%. The other side: Companies whose businesses have been crushed by the pandemic saw their share prices jump. The S&P 500's biggest gainers included Carnival Cruises and SL Green Realty, a major office building and shopping center landlord. Shares for those companies rose nearly 40% each.AMC, the world's largest movie theater chain, saw its stock jump as much as 63% on Monday. American Airlines and United both jumped 20%.The backdrop: Pre-market trading already pointed to a continuation of last week's election-fueled rally, but stocks skyrocketed once the Pfizer news hit.The big picture: Markets across Europe also shot higher. The STOXX 600 closed up 4%, its best day since March, according to Reuters. Editor's note: This story has been updated to reflect the stock market close.