(Adds dealer quotes, details, updates prices) * Loonie gains 1.9% in May * Canada posts first current account surplus since 2008 * Price of U.S. oil rises 0.9% * Canadian bond yields edge lower across the curve By Fergal Smith TORONTO, May 31 (Reuters) - The Canadian dollar was little changed against the greenback on Monday, notching its fourth straight monthly gain as oil rose and a recent surge in the administration of COVID-19 vaccines to Canadians bolstered the outlook for the domestic economy. With London and New York markets closed for holidays, the Canadian dollar was trading nearly unchanged at 1.2064 to the greenback, or 82.89 U.S. cents. For May, it was up 1.9%, extending a string of monthly gains that started in February. The currency was helped this month by higher commodity prices and a broadly weaker U.S. dollar, as well as a jump in Canadian vaccination levels, said Michael Goshko, corporate risk manager at Western Union Business Solutions. The Canadian economy "is going to come back very strongly in the second half of the year," Goshko said. The share of Canadians who have received at least one dose of a COVID-19 vaccine has soared to 57% from 33% at the start of the month, data from the Our World in Data project at the University of Oxford shows. Canada"s current account balance in the first quarter swung to a surplus for the first time since 2008, mainly boosted this year by exports of oil and lumber, data showed on Monday. Oil rose 0.9% on Monday, helped by growing optimism that fuel demand will grow in the next quarter, while the U.S. dollar fell against a basket of major currencies. . Canada"s GDP data for the first quarter is due on Tuesday and the May jobs report is due on Friday, which could offer clues on the Bank of Canada"s policy outlook. Canadian government bond yields eased across the curve, with the 10-year down 1.2 basis points at 1.488%. (Reporting by Fergal Smith; Editing by Bernadette Baum and Peter Cooney) Our Standards: The Thomson Reuters Trust Principles.