(Adds sales forecast, background)
Sept 13 (Reuters) - A U.S. Food and Drug Administration advisory panel on Wednesday voted 11-0 that the safety and efficacy of GlaxoSmithKline's Shingrix shingles vaccine warrants approval for its use in adults aged 50 and over.
Panel members said they were "very impressed" by the efficacy data from clinical trials of Shingrix, and that it represents an improvement over Zostavax, the current marketed shingles prevention vaccine from Merck & Co.
While the FDA is not required to follow the advice of its expert panels, it typically does so, with an approval decision expected in coming weeks.
Shingrix is considered one of the more important products in GSK's pipeline, with annual sales forecast to reach $1 billion by 2023, according to Thomson Reuters data.
Zostavax, approved in 2006, is expected to generate sales of about $730 million this year, with declining sales forecast for ensuing years with the introduction of serious competition.
Older people are most at risk of an outbreak of shingles, a painful, blistering rash. Shingles is the result of reactivation of the varicella-zoster virus, which causes chickenpox and remains latent in those who have had that disease.
In clinical trials, Shingrix has shown greater protection against shingles among older recipients than that demonstrated by Zostavax. Four years after injection, the GSK vaccine remained about 90 percent effective in people over age 70, while the efficacy of Zostavax declined noticeably over time.
Shingrix also reduces incidence of nerve pain following a shingles outbreak known as postherpetic neuralgia. (Reporting by Bill Berkrot; editing by Grant McCool)