By , (Reuters) -The S&P 500 ended lower on Monday, weighed down by Walt Disney, while Alexion Pharmaceuticals jumped on a $39 billion buyout offer from AstraZeneca in one of the year’s biggest deals.The Dow Jones Industrial Average hit a record high before ending lower, pulled down by Walt Disney.U.S. officials began to administer the vaccine developed by Pfizer and its German partner BioNTech on Monday following emergency-use approval from federal regulators last week.Shares of Disney, down 3.65%, and Pfizer, down almost 5%, weighed more than any other stocks on the S&P 500.The...…By , (Reuters) -The S&P 500 ended lower on Monday, weighed down by Walt Disney, while Alexion Pharmaceuticals jumped on a $39 billion buyout offer from AstraZeneca in one of the year’s biggest deals.The Dow Jones Industrial Average hit a record high before ending lower, pulled down by Walt Disney.U.S. officials began to administer the vaccine developed by Pfizer and its German partner BioNTech on Monday following emergency-use approval from federal regulators last week.Shares of Disney, down 3.65%, and Pfizer, down almost 5%, weighed more than any other stocks on the S&P 500.The...WW…