A decision on whether the UK Joint Committee on Vaccination and Immunisation will offer vaccination against herpes zoster to people aged 70-79 years is expected later this year.
The authors of this US cohort study note that vaccination against shingles is now recommended in the US for all immunocompetent adults over the age of 60 years; however the clinical trials supporting its efficacy were conducted in selected populations under controlled conditions. They therefore sought to determine the efficacy of the vaccine in unselected patients in routine clinical practice. This research was funded by an NIHR Clinician Scientist award from the National Institute for Health Research, UK Department of Health.
The study cohort comprised a 5% random sample of Medicare beneficiaries aged ≥65 years (n=766,330), of whom 3.9% (n=29,785) received herpes zoster vaccination during the study period (1st January 2007 to 31st December 2009). The main overall finding was that the incidence rate of shingles was 10.0 (95% CI 9.8-10.2) per 1,000 person-years in the unvaccinated group and 5.4 (4.6–6.4) per 1,000 person-years in those who received the vaccines, giving an overall adjusted vaccine effectiveness of 0.48 (95% CI 0.39–0.56). In immunosuppressed individuals, adjusted vaccine effectiveness was 0.37 (0.06–0.58). Among people who developed shingles, fewer who had been vaccinated had post-herpetic neuralgia at 90 days (vaccine effectiveness of 0.59; 0.21 to 0.79).
Limitations of this study include the possibility of exposure and outcome misclassification (based on the use of an administrative data source), possible underestimation of vaccine uptake, the observational nature of the data (vaccination was not randomised and could have been influenced by patient characteristics), the presence of unmeasured confounders (e.g. smoking and obesity; although these are not known to affect the development of incident zoster), and its relatively short duration (limits ability to determine long-term vaccine effects). Although vaccine effectiveness was assessed in individuals with immunosuppression, there were only small numbers (limiting the precision of vaccine effectiveness estimation) and adverse effects/ vaccine safety was not studied.