FDA reports pros, cons of experimental adult shingles vaccine

The FDA reported recently that Zostavax, Merck's experimental vaccine to prevent shingles, helps curb zoster-related pain but does not significantly affect the rate of death or hospitalization, according to regulatory staff in documents released recently. The finding was based on Merck data.

Studies also showed that the effectiveness of the adult zoster vaccine diminishes somewhat after three years. Age is also a factor in how well the vaccine works; the FDA reports that it is less effective in people 70 years and older. No "particular pattern" of serious side effects was noted.

The findings were issued before a meeting of outside health experts to discuss the vaccine and whether it will be recommended for approval by the FDA. One concern surrounding Merck's pediatric varicella vaccine (Varivax) is the durability of the immune response that it triggers—after the recommended single dose or a proposed second dose. A potential decline in varicella immunity through adulthood might put adults who were vaccinated in childhood at risk of painful, even debilitating, episodes of shingles.