Merck's shingles vaccine use expanded

The US Food and Drug Administration (FDA) has approved expanded usage of Merck's shingles prevention vaccine Zostavax, clearing the company to market the product for use in younger patients.

Zostavax is the only vaccine for shingles that is cleared in the US. A live attenuated virus vaccine, the product was approved for patients aged 60 and older in May 2006.

The new approval covers people between the ages of 50 and 59. The addition is significant because nearly everyone in that age group is at risk for developing shingles, according to Merck.

Merck now hopes that the US Centers for Disease Control will expand its current recommendation that Zostavax be administered to all appropriate candidates of 60 years of age and older to include the 50 to 59 year-old age group as well. The CDC's Advisory Committee on Immunization Practices (ACIP) is expected to vote on the issue later this year. The decision is key because most managed care companies use the ACIP's recommendations for determining their coverage of vaccines.

Shingles is caused by the resurfacing of the virus that causes chickenpox, which goes dormant but remains in the body. It is characterised by a rash of blisters that can cause severe pain and become debilitating, sometimes for years. The likelihood of shingles increases with age, and the condition affects about 200,000 healthy Americans between the ages of 50 and 59 each year.

The expanded approval was based on a multicentre study that showed that Zostavax reduced the risk of developing shingles by approximately 70 per cent. Conducted in the US and four other countries, the study enrolled about 22,000 people who were 50 to 59 years old, with half the subjects receiving Zostavax and half receiving placebo. Participants were then monitored for at least a year to see if they developed shingles.

Zostavax has annual sales of about $277m, which are lower than they might otherwise be due to a persistent shortage that means the drug has been on backorder for some time. Merck said it is investing more than $1bn to enhance manufacturing and increase supply.