Cost-Effectiveness of Herpes Zoster Vaccination: A Systematic Review

BACKGROUND: Herpes zoster (HZ) is one of the most common diseases among adults. Its reactivation is characterized by a severe and painful complication. In addition to the existing herpes zoster vaccine (ZVL), the FDA approved a new adjuvanted subunit zoster vaccine (RZV) in 2017 for use in adults aged 50 years and older. Several studies have assessed the cost-effectiveness of ZVL, many of which were conducted before the long-term vaccine efficacy data was available in 2014. OBJECTIVE: Our objectives were to (i) summarize and compare the cost-effectiveness analyses (CEAs) of ZVL conducted before and after 2014, (ii) summarize the CEAs of RZV, and (iii) critically assess the cost-effectiveness models and identify key parameters to consider for future CEAs of RZV. METHODS: We searched PubMed and two other databases from inception to March 2018 for original cost-effectiveness, cost-utility, or cost-benefit analyses of HZ vaccines. Three investigators independently reviewed and assessed full-text articles after screening the titles and abstracts to determine eligibility. For all included studies, we assessed study quality using the Drummond and Jefferson's checklist and extracted study characteristics, model structure, vaccine characteristics, incidence of HZ and complications, incremental cost-effectiveness ratio, and sensitivity analyses. We summarized data by type of vaccine, year of publication, and funding sources. RESULTS: Twenty-seven studies met eligibility criteria. All studies were from high-income countries and were of moderate-to-high or high quality. Twenty studies repeatedly used four cost-effectiveness models. The assumption on long-term efficacy of ZVL was not based on clinical trial data in > 50% of studies. Fifteen out of 25 studies concluded that ZVL was cost-effective compared with no vaccine at a vaccine price ranging between US$93 and US$236 per dose (2018 US$), 40% of which were published after 2014. All industry-funded studies favored the use of ZVL. The single study assessing RZV found it to be more effective and less costly than ZVL, and cost-effective compared with no vaccination. More studies conducted after 2014 included various efficacy endpoints for ZVL, adverse reactions, and productivity loss compared with those conducted before 2014. CONCLUSIONS: A majority of studies of ZVL found it to be cost-effective compared with no vaccine using the authors' chosen willingness-to-pay thresholds. RZV was dominant in the single study comparing the two vaccines, but the finding needs to be confirmed with further studies in different settings. Future studies should assume vaccine efficacy in line with clinical data, account for more efficacy endpoints for ZVL, and include other HZ long-term complications, vaccine adverse reactions, and productivity loss.