In the Shingles Prevention Study, half of the participants were assigned a single injection of the zoster vaccine and the other half a placebo vaccine. Neither the researchers nor the participants knew who received vaccine and who received placebo until after 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 occurred among those in the placebo group compared with only 315 in the vaccinated group. Among all vaccine recipients, the total burden of pain and discomfort due to shingles was 61 percent lower than in placebo recipients.
Zoster vaccine reduced the incidence of shingles by 63.9% in subjects aged 60 - 69 years of age and 37.9% in people aged 70 years or older.