Information has been received from a literature article, referring to 1099 patients of unknown age and gender. Information about concurrent conditions and medical history was not provided. On an unknown date the patients were vaccinated with zoster vaccine live (manufacture unknown) (strength, dose, frequency, lot#, expire date, dose# and route not reported). On an unknown date the patients experienced herpes zoster (HZ) despite vaccination (vaccination failure). The outcome of the events was not reported. The causality was reported as related. Background: Although it is evident that zoster vaccination reduces postherpetic neuralgia (PHN) risk by reducing herpes zoster (HZ) occurrence, it is less clear whether the vaccine protects against PHN among patients who develop HZ despite previous vaccination. Methods: This cohort study included immunocompetent patients with HZ. The vaccinated cohort included 1155 individuals who were vaccinated against HZ at age more than or equal to 60 years and had an HZ episode after vaccination. Vaccinated patients were matched 1:1 by sex and age with unvaccinated patients. Trained medical residents reviewed the full medical record to determine the presence of HZ-related pain at 1, 2, 3, and 6 months after HZ diagnosis. The incidence of PHN was compared between vaccinated and unvaccinated-patients. Study Participants. The authors identified a list of adults who were vaccinated against HZ at age more than or equal to 60 years after 01-JAN-2007 and had an episode of HZ after vaccination. Five potential unvaccinated patients with HZ were matched to each vaccinated patient with HZ for sex and date of birth (within 1 year). Diagnosis of HZ was identified from the outpatient setting by the International Classification of Diseases, Ninth Revision, Clinical Modification (ICD-9-CM) codes 053.xx. An index date, the date of HZ vaccination for the vaccinated patient, was also assigned to the matched unvaccinated patients. All patients with HZ were required to have more than or equal to 1 year of continuous membership before the index date and more than or equal to 6 months continuous membership before and after the HZ diagnosis. All patients with HZ had had no HZ diagnosis within 1 year before the index date. Because HZ vaccination is not recommended for immunocompromised patients, we excluded such patients from the study, defining them as those who had a diagnosis of human immunodeficiency virus infection, leukemia, or lymphoma or had received immunosuppressive agents within 1 year before the index date; patients who became immunocompromised after the index date were included in our analysis. Results: Thirty vaccinated women (4.2%) experienced PHN, compared with 75 unvaccinated women (10.4%), with an adjusted relative risk of 0.41 (95% confidence interval, 0.26-0.64). PHN occurred in 26 vaccinated men (6.0%) versus 25 unvaccinated men (5.8%), with an adjusted relative risk of 1.06 (0.58-1.94). These associations did not differ significantly by age. Conclusions: 1155 patients developed herpes zoster despite vaccination and 56 of them developed post herpetic neuralgia and 2 patients were hospitalized for HZ-related pain. Among persons experiencing HZ, prior HZ vaccination is associated with a lower risk of PHN in women but not in men. This sex-related difference may reflect differences in healthcare-seeking patterns and deserve further investigation. This is one of several reports received from the same literature (linked with 1506USA003540 and 1506USA002133). Additional information has been requested.