The shingles vaccine might not be cost-effective for people in their fifties, a new analysis suggests.

The Centers for Disease Control and Prevention (CDC) does not recommend the shingles vaccine for that age group, and the authors of the new analysis say their findings support that policy.

"Even though the vaccine is effective, it may not be cost effective," lead author Phuc Le of the Cleveland Clinic told Reuters Health.

Shingles, or herpes zoster, is a painful, blistering rash caused by the same virus that causes chicken pox.

About one million Americans develop shingles each year, Le and colleagues say. Many of them go on to have persistent severe pain known as postherpetic neuralgia, even if they receive treatment with antiviral drugs.

The vaccine against shingles is cleared for use among those age 50 and older, but the CDC's Advisory Committee on Immunization Practices (ACIP) does not recommend the vaccine before age 60.

For the new study, reported in Annals of Internal Medicine, the researchers used a computer to estimate the effectiveness of the vaccine in people 50 to 59 years.

Overall, they calculated, for every 1,000 people receiving the vaccine at age 50, just 25 shingles cases and one case of shingle-related pain would be prevented.

Typically, preventive treatments are considered cost-effective when they cost at most $100,000 per quality-adjusted life-year (QALY), that is, per year of healthy life gained. The new analysis found the vaccine cost over $300,000 per QALY.

Dr. Michael Rothberg, the study's senior author from the Cleveland Clinic, said that when the vaccine is given at ages 60 or 70, its protective effect lasts 10 to 12 years.

"If you get vaccinated when you're 50, you're pretty much unprotected by 60," he said.

In a statement emailed to Reuters Health, Dr. Eddy Bresnitz, the executive director of medical affairs for adult vaccines at Merck, said it's important not to lose sight of the impact of the disease.

Merck & Co., Inc.'s Zostavax shingles vaccine has been found to reduce both shingles and its related pain.

"Our FDA approved indication for Zostavax begins at age 50 and given the demonstrated efficacy rate of 70 percent for people 50 to 59 and safety profile of Zostavax, vaccination could help to prevent many of these cases," Bresnitz wrote. "This may help explain why many private insurance plans include the vaccine on formulary, in spite of the absence of an ACIP recommendation among the 50-59 age cohort."

If the vaccine's effectiveness lasted longer, or the price of the drug was less, it might be cost effective, Rothberg said.

But data on the longterm efficacy for people in their 50s may take years to be published, Le said in a follow-up email.

"The study already looks at the impact of vaccine cost," she said. "If the vaccine were to cost $80 or less per dose, the vaccine could be considered to represent good value for 50-year-olds. It's unlikely, though, that the vaccine will ever cost that little."

According to healthcarebluebook.com, a "fair price" for Zostavax in the U.S. is $200.

Rothberg said it may be worthwhile for people who have the money to spend.

"It's helpful, but it's not something health plans or the government should cover," he said. "It does benefit, but it's just a small benefit."