Abstract

Herpes zoster is a disease caused by the reactivation of the varicella-zoster virus. Risk increases with age, comorbidities, and immunocompromise. Globally, it represents a significant burden of disease, with an increasing incidence attributed to an aging population. It is estimated that one in three people will develop herpes zoster during their lifetime, with potential complications including postherpetic neuralgia, herpes zoster ophthalmicus, and disseminated forms in immunocompromised patients. In 2020, an estimated 14.9 million cases were reported among adults aged >= 50, with a projected 19.1 million by 2030. In Latin America, epidemiological data is limited, and in Chile the disease is not monitored. Consequently, for this recommendation, CAVEI had access solely to national data on hospital discharges with herpes zoster-related diagnoses, which may underestimate the actual burden of the disease. Between 2011 and 2024, there was a steady increase in hospital discharges, reaching 704 cases in 2024, with 70% of these involving people aged >= 50, and 52.3% being women. In April 2025, the Chilean Institute of Public Health approved a recombinant adjuvanted vaccine against herpes zoster for use in adults aged >= 50 and in people aged >= 18 at increased risk. This vaccine has been shown to be 97.2% effective in adults aged >= 50, with sustained protection of over 70% for up to 11 years. In immunocompromised individuals and those with comorbidities, efficacy was over 68%. The vaccine has high immunogenicity thanks to its adjuvant, which enhances both the humoral and cellular responses. Its safety profile is acceptable, although it is associated with mild to moderate transient local and systemic reactogenicity. Vaccination is cost-effective in most scenarios analyzed in the studies, with the strongest evidence in high-risk populations. In people with no comorbidities, the reduction in postherpetic neuralgia may be minimal. In light of these and other findings discussed in this document, CAVEI advocates for a phased implementation of the herpes zoster vaccination, using a two-dose regimen that initially prioritizes people aged >= 60 and immunocompromised individuals aged >= 18. A program extension to the 50-59 age group will be subsequently discussed, depending on epidemiological data and the national economic context. It is further recommended that systematic epidemiological surveillance be established to monitor the impact of vaccination and to strengthen the reporting and monitoring of Adverse Events Supposedly Attributable to Vaccination and Immunization in this population.