Objective. To assess the cost-effectiveness of the new adjuvanted herpes zoster subunit vaccine (HZ/su) as compared with that of the current live attenuated herpes zoster vaccine (ZVL), or no vaccine.
Design. Markov decision model evaluating 3 strategies from a societal perspective: (1) no vaccination, (2) vaccination with single dose ZVL, and (3) vaccination with 2-dose series of HZ/su.
Setting and participants. Data for the model were extracted from the US medical literature using PubMed through January 2015. Data were derived from studies of fewer than 100 patients to more than 30,000 patients, depending on the variable assessed. Variables included epidemiologic parameters, vaccine efficacy and adverse events, quality-adjusted life-years (QALYs), and costs. Because there is no standard willingness-to-pay (WTP) threshold for cost-effectiveness in the United States, $50,000 per QALY was chosen.
Main outcome measures. Total costs and QALYs.
Main results. At all ages, no vaccination was always the least expensive and least effective option, while HZ/su was always the most effective and less expensive than ZVL. At a proposed price of $280 per series ($140 per dose), HZ/su was more effective and less expensive than ZVL at all ages. The incremental cost-effectiveness ratios compared with no vaccination ranged from $20,038 to $30,084 per QALY, depending on vaccination age. The cost-effectiveness of HZ/su was insensitive to the waning rate of either vaccine due to its high efficacy, with initial level of protection close to 90% even among people 70 years or older.
Conclusion. At a manufacturer suggested price of $280 per series ($140 per dose), HZ/su would cost less than ZVL and has a high probability of offering good value.
Herpes zosters is a localized, usually painful, cutaneous eruption resulting from reactivation of latent varicella zoster virus. It is a common disease with approximately one million cases occurring each year in the United States . The incidence increases with age, from 5 cases per 1000 population in adults aged 50–59 years to 11 cases per 1000 population in persons aged ≥ 80 years. Postherpetic neuralgia, commonly defined as persistent pain for at least 90 days following the resolution of the herpes zoster rash, is the most common complication and occurs in 10% to 13% of herpes zoster cases in persons aged > 50 years [2,3].
In 2006, the US Food and Drug Administration (FDA) approved the ZVL vaccine Zostavax (Merck) for prevention of postherpetic neuralgia. By 2016, 33% of adults aged ≥ 60 years reported receipt of the vaccine . However, ZVL does not prevent all herpes zoster, particularly among the elderly. Moreover, the efficacy wanes completely after approximately 10 years . To address these shortcomings, a 2-dose HZ/su (Shingrix; GlaxoSmithKline) containing recombinant glycoprotein E in combination with a novel adjuvant (AS01B) was approved by the FDA in adults aged ≥ 50 years. In randomized controlled trials, HZ/su has an efficacy of close to 97%, even after age 70 years .
With the approval of the new attenuated herpes zoster vaccine, clinicians and patients face the question of which vaccine to get and when. The cost-effectiveness analysis published by Le and Rothberg in this study compare the value of HZ/su with ZVL vaccine and a no-vaccine strategy for individuals 60 years or older from the US societal perspective. The results suggest that, at $140 per dose, using HZ/su vaccine compared with no vaccine would cost between $20,038 and $30,084 per QALY and thus is a cost-effective strategy. The deterministic sensitivity analysis indicates that the overall results do not change under different assumptions about model input parameters, even if patients are nonadherent to the second dose of HZ/su vaccine.
As with any simulation study, the major limitation of this study is the accuracy of the model and the assumptions on which it is based. The body of evidence for benefits of ZVL was large, including multiple pre-licensure and post-licensure RCTs, as well as observational studies of effectiveness. On the other hand, the body of evidence for benefits of RZV was primarily informed by one high-quality RCT that studied vaccine efficacy through 4 years post-vaccination [4,6]. Currently, 3 other independent cost-effectiveness analysis are available. The Centers for Disease Control and Prevention model estimated HZ/su vaccine cost per QALY of $31,000 when vaccination occurred at age ≥ 50 years. The GlaxoSmithKline model, manufacturer of HZ/su vaccine, estimated a HZ/su vaccine cost per QALY of $12,000. While the Merck model, manufacturer of the ZVL vaccine, estimated a HZ/su vaccine cost per QALY of $107,000 . In addition to model variables, the key assumption by Le and Rothberg are based on the HZ/su vaccine cost at $140 per dose and ZVL at $213. The study results need to be interpreted carefully if the vaccine prices turn out to be different in the future.
Applications for Clinical Practice
The current study by Le and Rothberg demonstrated the cost-effectiveness of the new HZ/su vaccine. Since the study’s publication, the CDC has updated their recommendations on immunization practices for use of herpes zoster vaccine . HZ/su vaccine, also known as the recombinant zoster vaccine (RZV), is now preferred over ZVL for the prevention of herpes zoster and related complications. RZV is recommended for immunocompetent adults age 50 or older, 10 years earlier than previously for the ZVL. In addition, RZV is recommended for adults who previously received ZVL. Finally, RZV can be administered concomitantly with other adult vaccines, does not require screening for a history of varicella, and is likely safe for immunocompromised persons.
—Ka Ming Gordon Ngai, MD, MPH