Merck shingles vaccine effective in adults in 50s

In a huge study aimed at broadening the use of Merck & Co’s shingles vaccine, Zostavax reduced the incidence of the painful disease by 70 percent compared with a placebo in adults in their 50s, the company said.

The 22,439-subject study monitored adults aged 50 to 59 for at least one year after receiving either the vaccine or a placebo with 30 cases of shingles occurring in the Zostavax group compared with 99 cases in the placebo group. That translates into a reduction in incidence of shingles of 69.8 percent for Zostavax over placebo.

Based on the robust results, Merck said it has applied to the U.S. Food and Drug Administration for approval of Zostavax to prevent shingles in people ages 50 to 59. Merck said it is expecting an FDA approval decision for that population in the first half of 2011.

The vaccine is currently approved to prevent shingles, also known as herpes zoster, only in people aged 60 and older. In that population the vaccine has been shown to cut incidence of shingles by 51 percent.

Despite its efficacy, Zostavax sales have been disappointing and hampered by manufacturing snags, with the vaccine currently on back-order.

Zostavax had second quarter sales of just $18 million in the United States, down from $42 million in the year-earlier period. Merck said it expects to begin shipping the vaccine to fill current back orders before the end of the year.

There was a far higher incidence of adverse events overall reported in the vaccine group in the study - 72.8 percent versus 41.5 percent - primarily due to injection site reactions to Zostavax, researchers reported.

But researchers found a similar rate of serious adverse events between the two groups within 42 days and 182 days of receiving the vaccination. At 42 days the rate of serious side effects was 0.6 percent for Zostavax and 0.5 for placebo, while at 182 days the rate was 2.1 percent for the Merck vaccine compared with 1.9 percent for placebo.

Details of the study will be presented on Saturday at the Infectious Diseases Society of America meeting in Vancouver.

Shingles, an extremely painful, often debilitating disease that can last for months before it runs its course, is caused by the reactivation of the chickenpox virus.

There are about one million cases of shingles in the United States each year with about half occurring in people aged 60 years and older, according to the U.S. Centers for Disease Control and Prevention.

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By Bill Berkrot

NEW YORK (Reuters)