FDA has cleared Merck & Co. to market the first vaccine for people 60 years old and older against shingles, a painful disease caused by reactivation of the virus that causes chicken pox. About half of the estimated 1 million cases of shingles that occur in the U.S. each year occur in the elderly, according to Merck. The Zostavax approval is more welcome news for the company, which is facing thousands of lawsuits as it struggles to recover from the recall of its blockbuster painkiller Vioxx. Earlier this month, an FDA advisory committee endorsed the effectiveness and safety of Gardasil, a Merck vaccine designed to prevent cervical cancer. And in February, the company won U.S. approval for RotaTeq, its vaccine against rotavirus, the most common cause of severe diarrhea in children.