The results suggest the vaccine could prevent tens of thousands of shingles cases each year if it were offered to everyone who is eligible, the authors say.
Shingles is a rash that may be accompanied by severe pain, and is caused by the same virus that causes chickenpox. Studies suggest that about 25 percent of people may suffer from shingles at some point in their lives, and older adults are most at risk. Most shingles cases go away with medication, but occasionally patients continue to feel pain for months afterwards.
In 2006, the U.S. Food and Drug Administration approved a vaccine against shingles, made from a weakened form of the chickenpox virus, for adults over age 60.
While the vaccine had been tested before, its effectiveness had not been measured under the real-world conditions in regular doctors' offices, where researchers could not control who got the vaccine and how carefully it was handled.
According to the results, published in the Journal of the American Medical Association, about six out of every 1,000 people who were vaccinated got shingles each year. In comparison, 13 of every 1,000 unvaccinated patients in the study were diagnosed with shingles each year. The researchers calculated that for every 71 people who were vaccinated, one case of shingles was prevented.
Because they did not follow patients over the long term, the researchers do not know how effective the vaccine is years later, when its effects may start to wear off.