A study showed an outbreak reduction success rate of 51 percent.
An experimental shingles vaccine prevents about half of the chicken pox virus cases in older adults and results in milder episodes for those do who get the illness, according to the results of a large national trial.
Most people get chickenpox as children and endure a week or so of fever and itchy blisters brought on by the varicella zoster virus, a member of the herpes family. After chickenpox runs its course, it retreats to clusters of sensory nerve cells, usually located near the spinal cord, where it persists in a dormant state.
As the infected person's immune system strength wanes in old age, the virus can reactivate, multiplying and damaging sensory nerve cells to cause pain and then emerging on the skin in a blistery rash called shingles.
An estimated 600,000 to 1 million Americans are diagnosed with shingles every year, most of them over age 60. Half of all people who live to age 85 will get the disease. Pain and numbness from the nerve damage can persist for years, and in rare cases, can damage the eyes or even internal organs.
"For some people, shingles can result in months or even years of misery," said Dr. Michael Oxman, an infectious disease specialist at the San Diego VA Healthcare System and the University of California-San Diego who led the Shingles Prevention Study reported today in the New England Journal of Medicine.
The most debilitating effect of the disease is the chronic pain from the nerve damage, which patients typically describe as burning, throbbing, aching, stabbing or shooting, and which in the majority of patients is brought on by stimulation that is normally not painful, such as clothing touching the skin or being tickled by a cool breeze.
The vaccine trial "is very promising news for older persons," said Dr. Stephen Straus, an infectious diseases specialist at the National Institute of Allergy and Infectious Diseases, which collaborated with the VA on the 5 1/2 year study. "They indicate for the first time that we can use a vaccine to prevent shingles."
Since 1995, millions of American children have been protected from chickenpox with a zoster vaccine. The vaccine used for the older adults is a new, more potent version of the same vaccine made by the Merck Corp.
For the study, carried out in 16 VA medical centers and six medical facilities outside the VA, more than 38,500 men and women aged 60 or older got either a single injection of the zoster vaccine or a placebo. Neither the researchers nor the patients knew who got the real vaccine until the study was over.
During an average of more than three years of follow-up, the vaccine reduced the incidence of shingles by 51 percent: 642 cases of shingles were diagnosed in the placebo group but only 315 in the vaccinated group. Overall, the burden of pain and discomfort was 61 percent lower for the vaccinated group than for those getting the placebo, and episodes of severe pain were two-thirds less.
The shots were generally well tolerated, with few serious adverse events and some local varicella-like rashes at the injection site.
The researchers stressed that the vaccine was tested as a preventive therapy, and is not intended as a treatment for people already suffering from shingles.