Health

NEW YORK (CBS) ― An experimental vaccine has shown promise at preventing shingles, a painful skin rash that afflicts 1 million Americans every year and causes long-term excruciating nerve pain for some.

In a large study of older people, researchers reported that the vaccine cut the risk of shingles flare-ups in half and reduced their severity.

Shingles can attack anyone who has had chickenpox. The virus can lie dormant in the body and resurface as shingles years later. Talk show host David Letterman was off the air for five weeks when he had a case of shingles two years ago.

"A lot of people say, 'This is the worst pain I've ever had in my life,"' said Dr. Michael N. Oxman of the San Diego VA Healthcare System, who led the study of the experimental vaccine made by Merck & Co.

One study participant, 96-year old Robert Williams, is a retired doctor who told CBS News Medical Correspondent Elizabeth Kaledin he knows the pain shingles can cause.

"I knew the severity of the disease when the pain lasts a long time," Dr. Williams said. "Anything I could do to help modify this course I would be very willing to help with."

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 research reported in Thursday's New England Journal of Medicine was headed by the Veterans Affairs Department along with the National Institute of Allergy and Infectious Diseases and Merck, which helped fund the study.

To test the vaccine, researchers recruited 38,546 people who were 60 or older and had had chickenpox. That feat turned out harder than expected.

"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."

Volunteers got the vaccine or a dummy shot and were followed for about three years. The vaccine cut the number of shingles cases by 51 percent, the research showed. There were 642 shingles cases in the group that didn't get the vaccine, and only 315 in the vaccinated group.

The vaccine also reduced pain and discomfort by 61 percent and reduced long-term excruciating nerve pain, a serious complication, by two-thirds. Side effects were mild and included headaches and redness or swelling at the injection site.

"Unless you've experienced it, you just can't imagine something itching that bad," said Norman Telleson, one of the study volunteers who developed a mild case of shingles.

The 74-year-old from La Jolla, Calif., later learned that he had gotten the dummy injection. He said he tucked his arm inside his shirt to keep it from touching the rash on his abdomen.

"A light touch just drives you nuts," he said.

When Letterman went back to work after his bout with shingles, he told his audience: "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's nothing good about them.

Shingles, which gets its name from the Latin word for girdle or belt, usually starts with pain, tingling or itching in a band or patch on the torso, though it can occur on the face too. That's followed by a painful rash or blisters that can last for weeks. It's caused by a reactivation of the chickenpox virus, which retreats to nerve cells where it can remain dormant.

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

But the vaccine was only tested on people older than 60, so it's not clear if it will work as well in a younger population, Kaledin reports. The hope is it will, because everyone who's had chicken pox is at risk of getting shingles — that's most adults in the United States.

It can be treated with antiviral drugs but they must be used early. A case of shingles usually protects against another attack.

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.

"This is a different disease. The immune system of a baby and the immune system of the baby's grandparents are very different," explained Dr. Jeffrey L. Silber, who headed Merck's research team for the study.

Merck is seeking approval of the vaccine, called Zostavax, in the United States and Europe.

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

Dr. Donald H. Gilden of the University of Colorado Health Sciences Center in Denver said the shingles vaccine should be cost-effective because treating shingles is expensive. He said the chickenpox shot costs $50 to $100, and the more potent shingles vaccine might cost more.

Merck spokeswoman Christine Fanelle said the vaccine price isn't known yet.

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.

(© 2005 CBS Worldwide Inc. All Rights Reserved. This material may not be published, broadcast, rewritten, or redistributed. The Associated Press contributed to this report.)