It has been predicted that a quarter of the general population will be affected by HZV reactivation during their lifetime [7]. In the United States (US), an estimated one million cases of HZ infection occur each year, with an incidence of 11.12 cases per 1,000 patient-years and there are higher incidence rates and number of hospitalizations among older adults (> 50 years) [8-12]. Studies examining the general population of European countries demonstrated that the incidence of HZ in all ages ranges was from 1.2 to 4.8 cases per 1000 person-years and, among people > 60 years of age, it was 7.2 to 11.8 cases per 1,000 person-years [13,14]. Also, in a Spanish study, the majority of hospitalizations for HZ occurred in adults over 50 years of age [15]. In Italy, a regional survey conducted in 2007 reported a total incidence of 1.74 HZ cases/1000 population per year, over a period of 14 years and an incidence of hospital admissions of 0.12/1000 inhabitants, with an average cost of €4082.59 per hospitalization [16].

In 2006, an HZ vaccine was approved by the US Food and Drug Administration (US FDA) and recommended by the Advisory Committee on Immunization Practices (ACIP) for the prevention of shingles in individuals ≥ 60 years old. In the same year, European Medicines Agency (EMEA) gave its Marketing Authorization valid throughout the European Union to this product. EU approval states that the recommended age of vaccination starts from 50 yrs of age instead of 60 yrs of age as in the USA http://www.ema.europa.eu/humandocs/Humans/EPAR/zostavax/zostavax.htm. This new vaccine is made of the same live attenuated VZV strain used in the varicella vaccine, but it has a potency at least 14-times higher than that of single-antigen varicella vaccine, which is necessary to confer protection against zoster [17]. It boosts the CMI against HZ, thus reducing the incidence of the disease and severity [8,18-20]. Efficacy, safety and tolerability of a high titre VZV vaccine for the prevention of HZ infection and its sequelae were demonstrated in a multicentric study of over 38,000 older adults [9,10].

Nowadays, the vaccine is only distributed in USA; vaccination has been recommended in Austria and Switzerland and it should be soon included in European geriatric guidelines [21].

The Shingles Prevention Study, a case-control study examining the widespread immunization against VZV, established that the zoster vaccine was safe, well-tolerated, and effective at reducing the burden of illness due to HZ and the incidence of PHN [9,10,25-27].

In 2006, the US FDA licensed the HZ vaccine [8], which promises to reduce the morbidity and mortality of HZ. In fact, administration of the vaccine to younger people may offer a good cost-benefit balance [28].

The availability of a specific anti-zoster vaccine could offer an important tool for reducing health problems and improve the overall quality of life in the elderly, as demonstrated by several studies [29-32]. A combined immunization against both varicella in childhood and HZ in adulthood in the developed world could improve the control of the virus [23]. The future challenge is represented by the prediction of how the decrease in VZV circulation will affect immunity among both vaccinated and unvaccinated individuals: varicella will continue to occur even in a highly immunized population, because of the ability of VZV to reactivate as zoster. Studies have predicted that there will be an increase in HZ incidence until the adult population becomes predominantly composed of individuals with vaccine-induced immunity who do not harbour wild-type VZV [22]. Moreover, VZV vaccination in children, without optimal coverage, can shift the disease to adults, leading to severe illness and a higher incidence of herpes zoster. Vaccination strategies will likely need to be adjusted as the epidemiology of VZV and risk factors continues to evolve [33]. Some risk factors may help to redirect preventive vaccination strategies. Hicks et al. demonstrated that, in a cohort of non-immunocompromised subjects, there was a strong association between the development of HZ and a family history of HZ, suggesting that these individuals were at high risk for HZ infection. These individuals could be the primary target for vaccination, thus, decreasing both their possibility of VZV infection and health care expenditures due to HZ morbidity [34].

Age can also be considered as a risk factor: active HZV vaccination of individuals > 50 years of age, simultaneously or in sequence with anti-influenza vaccination, has been demonstrated to be an effective, well-tolerated strategy [35,36]. Few studies have been conducted to investigate the social and epidemiological problems related to shingles disease or to the spread of immunization. In a recent global survey about awareness, knowledge, symptoms and treatment of HZ among 8,688 adults ≥ 50 years of age in 22 countries, there was wide variation in HZ awareness among the different areas and, almost, universally poor knowledge of the causes and symptoms of HZ were reported. Moreover, the majority of respondents were unaware of their risk of HZ. This survey suggests a population-wide effort to improve global awareness of HZ would be required for a successful vaccine initiative [37].

In the Netherlands, Opstelten et al. evaluated the determinants of non-compliance with HZ vaccination in community-dwelling elderly to whom a free HZ vaccination was offered simultaneously with the yearly influenza vaccination. In all, 690 patients (39%) were vaccinated against HZ, while 1,349 patients (76%) accepted influenza vaccination. Determinants of non-compliance with HZ vaccination included the perceived lack of recommendation by the GP, unwillingness to comply with the doctor's advice, perception of low risk for contracting HZ, perception of a short pain duration for HZ and the opinion that vaccinations weaken natural immunity [38].

In the present study we have compared attitude, knowledge and experience about VZV-associated diseases of individuals from different age groups in two different regions in Italy. In both regions, the majority of subjects had been affected by varicella infection, while a low percentage (5%) had been vaccinated against VZV. Regarding perception and availability of the HZ vaccination, in both regions, adults over the age of 21 seemed to be willing to accept this vaccination. This is probably due to greater knowledge of the infection/disease in this population and to a direct, or indirect, experience with HZ in the older age group.

Finally, limits and biases of this study should be mentioned. A cross-sectional study measures the prevalence of an outcome of interest in a certain population at a certain time point or over a short period. We have explored the acceptability of the HZ vaccination in people using face to face interviews, carried out by their pratictioners and in university staff. We randomly selected the interviewed population in two Italian regions, Lazio and Campania. Indeed, each of the associations identified in the current study must be interpreted with caution because our sample is not representative of the entire Italian population and study inclusion or exclusion could have been mediated by the interviewer during the face to face interview. A cross-sectional design may also make it difficult to establish the cause and the effect, i.e., for this study, the vaccine acceptability versus the knowledge of the disease and the vaccine acceptability versus the age group.