Herpes Zoster and Frailty in Older Adults: a Systematic Review.

BACKGROUND

Herpes zoster (HZ) and its complications, postherpetic neuralgia (PHN), are common in adults, particularly the frail. Frailty may affect infection outcomes and vaccine efficacy. This study evaluated the association between frailty and HZ/PHN risk, and examined vaccine uptake, immunogenicity, and efficacy in frail versus non-frail individuals.

METHODS

We systematically reviewed PubMed/MEDLINE, the Cochrane Library, Embase, and grey literature for studies published from January 2015 to January 2025. Eligible studies included observational and randomized controlled trials evaluating frailty in adults aged ≥50 years and reporting HZ incidence, severity, PHN, or vaccination. Two reviewers independently selected studies, extracted data using a standardized form, and assessed quality using JBI tools. Due to heterogeneity, data were synthesized narratively.

RESULTS

Eight studies met the inclusion criteria, with a sample size exceeding 15,000 participants. Two studies identified an association between frailty and an increased incidence of HZ, while two others indicated an elevated risk of PHN among frail individuals. One study highlighted low vaccine uptake in a frail Italian cohort. Three studies assessed the immunogenicity of the zoster vaccine, suggesting that although absolute immune responses may be diminished in frail individuals, relative responses are often maintained. A pooled analysis of recombinant zoster vaccine trials demonstrated consistently high efficacy (exceeding 90%) across all frailty levels.

CONCLUSIONS

Frailty may increase vulnerability to HZ and PHN. Routine frailty assessment may improve vaccine uptake and prevention. Further longitudinal studies using standardized frailty measures are needed to understand the causal pathways and optimize care.