(For a Reuters live blog on U.S., UK and European stock markets, click LIVE/ or type LIVE/ in a news window.) * Trillium nearly triples on Pfizer’s $2.26 bln deal * GM to take $1 bln hit on expanded Bolt EV recall, shares slip * Futures up: Dow 0.44%, S&P 0.33%, Nasdaq 0.29% (Adds comment, details; updates prices) Aug 23 (Reuters) - Wall Street’s main indexes were set to open higher on Monday, with oil shares leading the pack, as investors returned to riskier assets after a sharp selloff last week that was fanned by worries about slowing economic growth. Oil majors Chevron Corp, Exxon Mobil, Schlumberger NV and Occidental Petroleum gained between 1.9% and 3.7% in premarket trading, tracking a 3% jump in crude prices. U.S. stocks were whipsawed last week by worries that a surge in cases of the Delta variant would further hurt the economy at a time when growth was already beginning to slow. The benchmark S&P 500 snapped a two-week winning streak, with the energy index sinking 7.3% on fears new COVID-19 curbs would hit fuel demand. By 8:15 a.m. ET on Monday, Dow e-minis were up 153 points, or 0.44%, S&P 500 e-minis were up 14.5 points, or 0.33%, and Nasdaq 100 e-minis were up 43.5 points, or 0.29%. Other economy-sensitive stocks also rose, with major Wall Street banks up about 1%. The Federal Reserve’s annual economic symposium in Jackson Hole, Wyoming, will now be closely watched for cues on when the central bank would start to taper its massive pandemic-era stimulus. The summit will be held virtually, on Aug. 27, for a second straight year. “People are expecting that the accommodative positioning of the Fed will stay in place for at least another handful of months as Delta has given the Fed to do nothing in the short term,” said Thomas Hayes, managing member at Great Hill Capital in New York. “When you have so much liquidity in the system and there’s not any other place to go with rates so low ... investors who have bought these dips have been amply rewarded. So I don’t see that changing until when they announce taper.” IHS-Markit’s flash reading of U.S. business activity, due at 9:45 a.m. ET, is expected to retreat in August to 58.3 from 59.9 in July. Apple Inc, Microsoft Corp, Amazon.com , Google-owner Alphabet Inc and Tesla Inc were all up between 0.3% and 0.8% before the opening bell. U.S.-listed shares of Trillium Therapeutics Inc surged 191.1% after Pfizer Inc agreed to buy remaining shares of cancer drug developer it does not already own in a $2.26 billion deal. Pfizer shares also added 3.4% ahead of a potential full U.S. approval for its COVID-19 vaccine. General Motors Co fell 1.5% after the largest U.S. automaker said it would take a $1 billion hit to expand the recall of its Chevrolet Bolt electric vehicles due to the risk of fires from the high-voltage battery pack. (Reporting by Devik Jain in Bengaluru; Editing by Anil D’Silva) Our Standards: The Thomson Reuters Trust Principles.