Originally published by 2 Minute Medicine® (view original article). Reused on AccessMedicine with permission.

1. For individuals over age 50 who received the live zoster vaccine, protection against herpes zoster, postherpetic neuralgia, herpes zoster opthalmicus, and hospital admissions was strongest in the first year and waned substantially over the follow-up period.

Evidence Rating Level: 1 (Excellent)

Herpes zoster (HZ) is the virus responsible for shingles, a painful rash that can develop in anyone previously infected with varicella zoster. Complications of HZ include postherpetic neuralgia and herpes zoster opthalmicus, with few patients requiring hospital admission. This prospective cohort study aimed to assess the vaccine’s effectiveness in preventing HZ and its complications within 10 years of immunization. The study was conducted by analyzing the electronic health records of 1,505,647 individuals over age 50 between January 2007 and December 2018. All individuals were unvaccinated for HZ at the start of the study period. Of this cohort, 34% of participants were vaccinated with the live zoster vaccine. Over the follow-up period, there were 75,135 incident HZ cases, of which 7% developed postherpetic neuralgia, 6% developed herpes zoster opthalmicus, and 0.7% required hospital admission. For all of these outcomes, the effectiveness of the vaccine was greatest in the first year after immunization but decreased over time. For protection against herpes zoster, the vaccine’s effectiveness decreased from 67% (95% CI, 65%-69%) in the first year to 15% (5%-24%) at 10 years. For protection against postherpetic neuralgia, the vaccine’s effectiveness decreased from 83% (78%-87%) to 41% (17%-59%) over 10 years. Similar trends were observed for herpes zoster opthalmicus and hospital admissions. A limitation of this study is that the researchers required the presence of both a diagnosis and antiviral prescription to count a case of HZ, and as such, the number of incident cases may have been underrepresented. Overall, this study demonstrates that the live zoster vaccine was effective in preventing HZ and its complications, but the protection waned substantially over the 10-year follow-up period.

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