A varicella-zoster virus vaccine reduced the burden of illness of herpes zoster in older adults.

Outcomes: vaccine efficacy with respect to the severity of illness caused by herpes zoster, defined as the relative reduction in burden of illness score (VEBOI) based on the severity of herpes zoster pain and its duration, comparing the vaccine and placebo groups. For the vaccine to be considered a success, the VEBOI point estimate had to be >47% with the lower limit of the 95% CI .25%. The secondary outcome was vaccine efficacy with respect to the incidence of post-herpetic neuralgia (VEPHN) defined as pain rated as >3 (scale ranged from 0–10 [pain as bad as you can imagine]). The vaccine was considered a success if the VEPHN point estimate was >62% with a 95% CI lower limit .25%.