Study Highlights Importance of Zoster Vaccination for Older Adults

Herpes zoster and postherpetic neuralgia can cause a significant health burden among adults 65 years of age and older.

A recent study indicates that zoster vaccine live (Zostavax) may be effective at reducing hospitalization from herpes zoster (HZ) and postherpetic neuralgia (PHN) among older adults, according to a study conducted in New Zealand published in The Lancet Regional Health.1

Zoster vaccine live (ZVL), also called the live-attenuated zoster vaccine, is no longer available for use in the United States, as of November 18, 2020. The CDC advises US residents who previously received ZVL to seek vaccination with the zoster vaccine recombinant, adjuvanted (Shingrix).2

As such, the authors of the current study sought to evaluate the real-world efficacy of ZVL among older adults in New Zealand.

“The safety, efficacy and effectiveness of ZVL has been previously demonstrated in clinical trials, but further evidence is needed from national real-world observational studies. In [New Zealand], the single-dose ZVL (also known as the live-attenuated zoster vaccine) was approved on the 1st of April 2018 for use in adults ≥ 50 years old and is available for no charge, to people aged ≥ 65 years (with a catchup for ages 66–80 years which ran from 2018–2021),” the study authors wrote. “To our knowledge, since the vaccine was introduced, no HZ vaccine effectiveness analysis has been carried out in [New Zealand]. Data are also lacking on how the vaccine performs for indigenous peoples and there are few analyses of vaccine effectiveness and associated complications performed using whole national population data.”

HZ and its associated complications cause a significant health burden among older adults. An HZ vaccination program was launched in New Zealand in April 2018 with a single-dose of the vaccine administered to adults 65 years of age and up with a 4-year catch up for those between 66 and 80 years of age.

The study authors conducted a nationwide retrospective matched cohort study from April 1, 2018, to April 1, 2021, using data from a linked, de-identified patient level Ministry of Health platform. The investigators estimated the efficacy of ZVL against HZ and PHN adjusting for covariates using a Cox proportional hazards model.

The analysis included 824,142 New Zealand residents, with 274,272 vaccinated individuals with ZVL matched with 549,870 unvaccinated individuals. The matched population was 93.4% immunocompetent, 52.2% female, 80.2% European, and 64.5% were between 65 and 74 years of age with a mean age of 71.1±5.0.

Incidence of hospitalized HZ cases among vaccinated individuals was 0.16/1000 person-years compared with 0.31/1000 person-years among unvaccinated individuals. Incidence of hospitalized PHN was 0.03/1000 person-years among vaccinated individuals compared with 0.08/1000 person-years for unvaccinated individuals.

The primary analysis found that the adjusted overall vaccine efficacy against hospitalized HZ and hospitalized PHN was 57.8% (95% CI: 41.1–69.8) and 73.7% (95% CI:14.0–92.0), respectively. Among adults ≥ 65 years old, vaccine efficacy against hospitalized HZ was 54.4% (95% CI: 36.0–67.5) and vaccine efficacy against hospitalized PHN was 75.5% (95% CI: 19.9–92.5).

A secondary analysis showed vaccine efficacy against community HZ was 30.0% (95% CI: 25.6–34.5). Vaccine efficacy against hospitalized HZ among immunocompromised adults was 51.1% (95% CI: 23.1–69.5), whereas PHN hospitalization was 67.6% (95% CI: 9.3–88.4).

“Given the negative impact of HZ and associated complications on the overall quality of life, further evaluation should take place as the HZ vaccination program matures. As other HZ vaccines become available in [New Zealand], given the differences between real-world effectiveness and clinical trials, further studies will be needed,” the study authors wrote. “Future observational studies using well powered national data will also be needed to assess whether ZVL [vaccine efficacy] wanes against HZ and associated complications amongst older people in [New Zealand]. Also, there a need to understand how [vaccine efficacy] differs amongst immunosuppressed people at different stages of treatment.”

References

1. Mbinta, J.F. et al. Herpes zoster vaccine effectiveness against herpes zoster and ..., The Lancet. Available at: https://www.thelancet.com/journals/lanwpc/article/PIIS2666-6065(22)00216-4/fulltext. Accessed December 12, 2022.

2. What Everyone Should Know about the Shingles Vaccine (Shingrix). CDC. Website. https://www.cdc.gov/vaccines/vpd/shingles/public/shingrix/index.html. Accessed December 12, 2022.

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