Herpes zoster vaccine: a protection for the elderly.

The Herpes Zoster vaccine is strongly recommended by the World Health Organization to promote healthy aging by preventing the corresponding age- related disease, also named shingles. The disease is due to the endogenous reactivation of Varicella Zoster Virus, the causal agent of chickenpox, that becomes latent at the peripheral nervous system level. Here, owing to the host's cell-mediated immunity, it may be confined for several decades. However, the immune senescence allows the possibility of virus reactivation, causing the onset of neuropathic pain and skin rash that characterize the acute disease. Sometimes, the neuralgia becomes chronic causing postherpetic neuralgia that has a significant impact on the quality of patient life, analogously to the ophthalmic HZ, a particularly feared form of disease. Due to the causal relationship between decreasing immune defenses and virus reactivation with disease onset, the incidence of Herpes Zoster, in Italy now equal to 6.42 (95%CI: 5.93-6.95) cases per 1,000 people per year will increase steadily in the future due to the longevity rise of the population. Considering epidemiological impact, complications and sequelae in the short- and long-term, costs of clinical-therapeutical management of patients, and, above all, the poor effectiveness of available therapy the only effective intervention is vaccination of the elderly. Currently in the European Union, there is only one vaccine for Herpes Zoster prevention, formed by live attenuated OKA-Merck virus strain that is also used for paediatric vaccine. According to the Health Technology Assessment surveys, the intervention cost (based on "Quality Adjusted Life Years") is clearly below the discriminating threshold value to judge the feasibility and, as predicted by the Italian National Plan of Vaccinal Prevention 2017-2019, the vaccine is offered free to all subjects >65 years.