(Reuters) - European stocks closed higher on Wednesday as more positive updates on COVID-19 vaccine and merger activity in the region helped offset worries about the fast-spreading virus. The pan-European STOXX 600 index .STOXX rose 0.4%, returning to a more than eight-month high hit earlier this week. Economically sensitive stocks such as automakers .SXAP, banks .SX7P, miners .SXPP and retailers .SXRP rose more than 1%, leading sectoral gains. After a sluggish start, European bourses got a boost from news that final results from Pfizer Inc"s PFE.N COVID-19 vaccine trial showed its shot had a 95% success rate and two months of safety data, paving the way for it to apply for an emergency U.S. authorization. However, the market response was measured as investors expect any vaccine rollout to take time, while more U.S. and European restrictions in the absence of fresh stimulus could weigh on economic activity. “If a vaccine were somehow to be available even by December, that would be great. But the impact is going to be very marginal,” said Chris Beauchamp, chief market analyst at IG. “Investors are aware that a vaccine will be here eventually and some (stimulus) needs to come in fairly soon to provide that bridge through the difficult period.” “That will provide the catalyst for a big move higher.” The number of reported global daily deaths from the novel coronavirus stood at the highest ever on Tuesday, according to a Reuters tally. Britain reported the highest number of deaths in Europe. Despite shutdown worries, the STOXX 600 remains on track for its best month on record as investors bet on a global economic recovery, supported by trillions of dollars in stimulus and hopes of a vaccine. M&A also drove big swings in stocks, with Britain"s RSA Insurance RSA.L gaining 4.6% after it backed a 7.2 billion pound ($9.55 billion) cash offer from Canada"s Intact Financial and Denmark"s Tryg in one of Europe"s biggest financial takeover bids this year. Deutsche Boerse DB1Gn.DE rose 2.4% after the German stock exchange operator said it would acquire an 80% stake in corporate governance adviser Institutional Shareholder Services (ISS) for about $1.8 billion. Among decliners, German automotive supplier Schaeffler SHA_p.DE fell 5.3% after it set mid-term sales targets that disappointed investors. Shipping group Maersk MAERSKb.CO slipped 1.0% after it reported quarterly sales and operating profit in line with previous forecast and maintained its earnings forecast.