Retiree Norman Telleson didn't know much about a painful skin rash called shingles (search) when he volunteered for a study of an experimental vaccine to prevent it.

But he soon found out when he developed a mild case a year later.

"Unless you've experienced it, you just can't imagine something itching that bad," said the 74-year-old from La Jolla, Calif.

Turns out Telleson didn't get the vaccine but a dummy shot given to half of the 38,546 people enrolled in the test. Otherwise, he might have fared better.

Researchers reported Thursday in the New England Journal of Medicine (search) that the vaccinated test group had half as many cases of shingles. Those who got it had a milder case, and there were far fewer cases of lasting excruciating nerve pain.

"We're just overjoyed that it actually worked," said Dr. Michael N. Oxman of the San Diego VA Healthcare System, who led the study of the vaccine made by Merck & Co.

The research was spearheaded by the Veterans Affairs Department (search) along with the National Institute of Allergy and Infectious Diseases and Merck, which helped fund the study and is seeking approval of the vaccine in the United States and Europe.

Shingles can attack anyone who has had chickenpox (search), and an estimated 1 million Americans are afflicted every year. The chickenpox virus can lie dormant in nerve cells and resurface as shingles years later.

But when the researchers tried to sign up volunteers over 60 who had had chickenpox, they discovered they had to explain the disease first.

"It turns out that most people thought shingles was something you had on your roof," said Oxman. "We ended up doing a lot more work than we planned."

If the vaccine is approved by the federal government, it could eventually be added to the shots recommended for older Americans. Unlike traditional vaccines which prevent a new disease, the shingles shot would keep a long-ago acquired infection in check.

"The possibility that a feared consequence of aging may be minimized or avoided is an important advance," Dr. Ann Arvin of Stanford University School of Medicine wrote in an accompanying commentary in the journal.

In the VA test, volunteers got the vaccine or a dummy shot and were followed for about three years. There were 315 cases of shingles in the group that got the vaccine, about half the 642 shingles cases in the group that didn't, the researchers said.

The vaccine also reduced pain and discomfort by 61 percent and reduced long-term severe nerve pain, a serious complication, by two-thirds.

As people age, their immunity to the dormant chickenpox virus wanes and it can re-emerge as shingles. Those with weakened immune systems are also at risk.

Shingles, which gets its name from the Latin word for girdle or belt, usually starts with pain or itching in a band on the skin, followed by a rash or blisters.

Treatment includes antiviral drugs but they must be used early. A case of shingles usually protects against another attack.

Talk show host David Letterman had a case of shingles two years ago, and on his first night back said: "It hurt so much I was Michael Jackson-crazy." He devoted his Top 10 List to all the good things about shingles — then declared there were none.

The vaccine tested in the VA study was a stronger version of the chickenpox vaccine that has been given to children in the United States since 1995.

"We will be evaluating how long the vaccine benefit lasts and ... whether subsequent doses would be needed, and if so, when," said Dr. Jeffrey L. Silber, who headed Merck's research team for the study.

While the vaccine's price isn't known yet, Dr. Donald H. Gilden of the University of Colorado Health Sciences Center in Denver said it should be cost-effective since shingles is expensive to treat.

Gilden, who wrote an editorial in the journal, compared having chickenpox as a child to his own brief but painful case of shingles on his arm three years ago.

"I think grown-ups need the vaccine more than the kids do," he said.