LONDON, October 26 (Reuters): One of the world's leading COVID-19 experimental vaccines produces an immune response in both young and old adults, raising hopes of a path out of the gloom and economic destruction wrought by the novel coronavirus. The vaccine, developed by the University of Oxford, also triggers lower adverse responses among the elderly, British drug maker AstraZeneca Plc, which is helping manufacture the vaccine, said on Monday. A vaccine that works is se