Varicella zoster virus (VZV) is a member of the Herpesviridae family and is an enveloped double-stranded DNA virus. Primary infection with VZV causes varicella, commonly known as chickenpox. The virus migrates to the sensory ganglia and establishes latency, by which the affected individual becomes asymptomatic. Reactivation of the virus causes herpes zoster (HZ), also known as shingles.1

Infection with VZV is the highest reported notifiable infectious disease in Hong Kong, with 8879 cases reported in 2016.2 A study in 1994 showed that antibodies against VZV were found in more than 90% of children by 8 years of age,3 illustrating that latent infection was highly prevalent. These individuals would be at risk of HZ.

Studies report the lifetime prevalence of HZ to be approximately 10% to 32%.1 4 The University of Hong Kong estimated the prevalence of HZ to be 16.8%.5 The incidence of HZ is positively correlated with age.6 Individuals who are immunocompromised7 or have a chronic disease8 may be at a greater risk of having HZ.

The viral disease HZ presents with a rash with dermatomal distribution, accompanied by vesicular eruption and neuropathic pain.7 A number of complications can result from HZ.9 Post-herpetic neuralgia, a persistent neuropathic pain in the area affected by HZ, can develop particularly in older adults.9 10 Other serious sequelae include HZ ophthalmicus, HZ oticus and bacterial skin infections, all of which adversely affect the quality of life of patients.9 These also place a significant economic burden on the health care system.11 In 2009, a study estimated the cost of treating new HZ cases in the US to be over one billion US dollars each year.12 Active HZ can be treated by antiviral therapy, such as acyclovir.7 13

The vaccine for HZ is a live vaccine approved by the Food and Drug Administration (FDA) of the US in 2006 for the prevention of HZ in immunocompetent patients aged 60 years or above.14 The vaccine has been approved for use in Hong Kong since 2007.13 The FDA approved the use of the vaccine in individuals aged 50 to 59 years in 2011.15 According to the Shingles Prevention Study,16 HZ vaccine lowered the incidence of HZ by 51% and reduced the pain and discomfort of postherpetic neuralgia by 66% when compared with placebo. Similar studies to assess public awareness of HZ and its vaccination were then carried out. The Herpes Zoster Global Awareness Survey from 22 countries17 and a knowledge, attitude, and practice study in South Korea18 were conducted in 2009 and 2015, respectively. Factors promoting or limiting the prevalence of vaccination against HZ were also investigated in the latter study.18

There has been limited research conducted in the Hong Kong population to assess the knowledge of and attitudes towards HZ and the practice of vaccination. This study aimed to explore these areas.

A cross-sectional survey was conducted in 11 clinic sessions during 24 July to 12 August 2015 at the Sai Ying Pun Jockey Club General Outpatient Clinic (GOPC). The GOPC is open to the general public and serves all patients who comprise mainly those with chronic or episodic disease. There were 6330 patients attending the clinic during the study period, of which approximately three quarters aged 50 years or above. These patients in the waiting area of the clinic were selected by convenience sampling to participate in this study. No additional criteria were set to allow for a higher degree of generalisability. Participants were asked to complete a face-to-face questionnaire after giving written informed consent. They were allowed to either complete the questionnaire themselves, or listen to the researcher reading the questions aloud without any additional interpretation, then answer the question verbally. Approval was obtained from the Institutional Review Board of the University of Hong Kong/Hospital Authority Hong Kong West Cluster and the GOPC prior to commencement of this study.

A questionnaire consisting of 30 items was designed; this included questions on demographics (n=3), medical history (n=4), whether the respondent had heard about HZ (n=1), knowledge of HZ (n=8) and HZ vaccination (n=6); attitudes towards preventing HZ (n=7); and whether the respondent would consider vaccination against HZ (n=1).

To estimate the proportions of participant responses to the questions about knowledge of HZ, for 95% confidence level with an expected true proportion of 50% and 5% margin of error, a sample size of 385 was obtained using the formula:
N=Z²p(1−p)/C²
where N=sample size, Z=Z value, p=population variance, and C=margin of error

To analyse the number of correct responses associated with five demographic factors with an effect size (f²) of 0.15 and a statistical power of 0.8, an a-priori analysis was employed to obtain the sample size of 92 to achieve a 5% margin of error, using G*Power (version 3.1.9.2) and the following formulae19:
N=λ/f² and N=v+u+1
where N=sample size, λ=non-centrality parameter, f²=effect size, v=degree of freedom of the denominator of the F ratio, and u=number of predictors

Statistical analysis was performed with SPSS (Windows version 23.0; IBM Corp, Armonk [NY], US). Demographic data, medical history, respondents’ attitude towards preventing HZ and decision about HZ vaccination were analysed by descriptive statistics. Regarding knowledge of HZ, the number of correct responses out of eight questions was calculated. Multiple linear regression analysis was used to evaluate the association of the number of correct responses with age, gender, educational attainment, history of HZ, and history of chronic diseases. Chi squared tests were applied to evaluate the associations in giving correct response to each question among the same five variables. A P value of <0.05 was considered significant.

A total of 496 persons were invited to participate in the study, of whom 430 agreed which corresponded to a response rate of 87%; 408 valid responses were collected. The sample was not weighted by the population because the male-to-female ratio was similar to that of the population (48:52).20 The demographic data are shown in Table 1. Approximately 40% of respondents did not know their history of chickenpox despite its high prevalence, whereas over 95% had heard of the condition of HZ. Although some respondents did not understand the medical terminology “herpes zoster”, most of them knew the Cantonese colloquial name (生蛇).

Table 2 summarises the responses to the eight questions pertaining to the knowledge of HZ, in which 16 respondents who had never heard of the condition were excluded. Only 29.6% knew that chickenpox and HZ are related. Over half were unsure of the lifetime prevalence of HZ. Immunocompromised state was a well-known risk factor of HZ (84.7%). Over 70% were aware that VZV can reactivate in young ages. Rash, blisters, and neuropathic pain were the most commonly known symptoms of HZ, identified by 85.7% of respondents. Nonetheless 13.3% did not know the symptoms of HZ even though they had heard of the disease.

There is a saying in Chinese society that death will ensue when the rash of HZ circumvents the body. Worryingly, only slightly less than half (48.7%) knew that this was untrue, 18.9% thought the statement was true and the remaining were unsure. Additionally, 69.6% gave the correct response that contacts of HZ patients could not acquire HZ infection directly, and 72.2% knew that HZ was treatable.

Respondents scored a mean (±standard deviation [SD]) of 4.96 (±1.72) correct responses out of eight. Over half of all subjects answered five or six questions correctly.

Of 392 participants who had heard of HZ, 11 respondents who were uncertain of their history of HZ were excluded from the multivariate regression analysis regarding the knowledge of HZ (Table 3a). The number of correct responses was positively correlated with educational attainment (P=0.026) and history of HZ (P=0.038), but negatively correlated with age per year (P<0.001) and male gender (P=0.029).

The results of the Chi squared tests and the corresponding odds ratios are shown in Table 3b. Respondents aged 65 years or above were half as likely as those aged 50-64 years to give correct responses regarding the relationship between chickenpox and HZ (P=0.007), the higher risk of HZ among immunocompromised individuals (P=0.027), and the misconception of death associated with a circumventing rash  (P=0.003). In contrast, participants with higher educational attainment were more likely than those without to give appropriate answers to the latter two questions (P=0.008 and P<0.001, respectively).

Respondents with a history of HZ (P=0.001) and those with higher educational attainment (P=0.028) were more likely to correctly identify the symptoms of HZ.

Of 392 respondents, 148 (37.8%) had heard of the HZ vaccine. Only this subgroup was asked to answer four additional questions about the vaccine (Table 4). One respondent who did not answer the questions was excluded. On average, 1.73 (±1.00) out of four responses were correct.

Nearly half of these respondents (46.9%) correctly identified the target age-group for HZ vaccination and 24.5% thought there was no age limit. Most subjects did not know that vaccination is possible regardless of history of chickenpox or HZ. Around two thirds (68.0%) were aware that the vaccine can significantly reduce the incidence of HZ, but only 49.7% knew that the vaccine is not indicated for treatment of active disease.

Table 5 gives a breakdown of the seven questions about attitudes of respondents to HZ. Over half (52.2%) of 391 respondents (with one participant who did not answer the questions being excluded) thought they had an insufficient understanding of HZ. Almost two thirds were interested in learning more about the disease (66.2%) and its prevention (66.0%). A similar percentage of subjects (64.5%) remarked that there were inadequate channels to learn about prevention of the disease. While 76.7% believed that HZ could affect their health significantly, only 35.0% were worried about getting the disease. Almost one third (30.4%) said that they could afford the HZ vaccine.

Among the subgroup who had heard of the HZ vaccine, 140 (94.6%) replied that their doctor had not mentioned or recommended the vaccine.

This study compared the vaccination rate for HZ with that of influenza and pneumococcus. The latter two vaccines are recommended by the Centre for Health Protection for those aged above 65 years and are included in the Elderly Vaccination Subsidy Scheme.21 Enquiry revealed that 26.9% and 14.3% of 391 respondents had taken the influenza vaccine in the past year and pneumococcal vaccine in the past 5 years, respectively. The figures were much higher than that for HZ vaccination (2.8%).

When asked about the reasons for not having HZ vaccination, approximately half (47.1%) replied that they were unaware of its availability. This was followed by inadequate promotion from doctors and public education (32.4%), the relatively high cost of the vaccine (28.4%), and good self-perceived health (20.3%). Lastly, 17.2% replied that they would consider HZ vaccination in the future.

This study attempted to investigate the knowledge, awareness, and attitudes towards HZ and its vaccination among citizens aged 50 years or above in Hong Kong. The results were informative. They revealed that the general public do not have adequate knowledge about the diseases caused by VZV or awareness regarding the prevention of HZ. This corroborates the general opinion of having an inadequate understanding of the disease. Similar findings have been observed in other countries according to a global survey,17 in which around 67% subjects stated they had little or no knowledge about HZ.

Few respondents in this study knew that chickenpox (varicella zoster) and shingles (HZ) are caused by the same virus. Similar results have been reported by the Public Opinion Programme, the University of Hong Kong (HKUPOP).5 Certain misconception about the disease persists—death from a rash circumventing the body—is still a commonly believed myth among the middle-aged and the elderly people. This study found that the proportions of respondents who were aware of HZ and its vaccination were comparable with those reported by a study in South Korea.18

There was a significant association between educational attainment and the correct responses regarding knowledge of HZ. The positive correlation between a history of HZ and the number of correct responses, however, was only marginally significant. There may be several reasons. Physicians may not have given patients enough information about the disease with consequent persistence of misconceptions. Patients who have had the disease should not be presumed to have a better understanding than those who have not. Moreover, participants might be relatively less aware of HZ due to its less life-interfering nature: only 35% were concerned about getting the disease. Despite the relatively low perceived risk, approximately 77% opined that HZ would have a significant effect on their health, whilst 66% admitted an interest in knowing more about the disease and its prevention. Similar observations have been reported in other countries,17 where 26% predicted that they were likely to have HZ in the future, and 70% indicated that they would ask their doctors about HZ vaccination.

This study found that over 60% of respondents showed disagreement regarding whether there was sufficient accessibility to information about the prevention of HZ. This may contribute to a lack of awareness of the HZ vaccine as the most common reason in our study for non-vaccination. This serves to emphasise the substantial role of doctors in health promotion regarding HZ in future.

According to the study conducted in South Korea,18 although 85.8% of participants would consider vaccination against HZ initially, the figure fell to 59.6% when they took account of the associated cost. On the contrary, HZ vaccination was considered by 17.2% and 36.0% of respondents in this study and in the survey led by HKUPOP,5 respectively, suggesting that HZ vaccination is currently not widely accepted by the community. The situations in Hong Kong and South Korea are similar to some degree since participants expressed some interest in vaccination but associated cost and recommendations from doctors were key influences on a decision about whether or not to vaccinate.

This study could be subject to selection bias because participants were recruited via convenience sampling in one clinic only. The results obtained from this study may have limited generalisability to the GOPC setting and the general population. In future studies, representative samples may be recruited from clinics in various districts and specialties to achieve a more diverse group of people and to further confirm the associations.

Several survey responses were invalidated. For instance, some people claimed that they had not had chickenpox before but had had HZ. This is biologically implausible and may be because most people got chickenpox as an infant or child.1 3 8 This hinders accurate recall unless family member can help. Recall bias is another recognised limitation of this study. Patients with a history of HZ or other chronic diseases usually pay greater attention to their health. Their medical history was subject to self-reported bias since such information could not be retrieved from their medical records.

Another source of bias comes from non-response. Those who refused to participate in the survey (13%) stated that they were unfamiliar with the disease. The results of this study may also be affected by responses that were speculative, as reflected by the observation that some respondents tended to guess rather than answer “uncertain or do not know”. These factors may overvalue the level of understanding of the disease among the general public that could have been improved by a pilot study to design questions with clear wordings and simple language. A pilot study would help identify respondents’ strategies in answering specific questions that required recall, to better evaluate their understanding of HZ, and establish the limits of recollection, with the effect of minimising bias, and enhancing accuracy and response completeness.

Further studies may be initiated to investigate the epidemiology of HZ in Hong Kong, and clarify whether there are significant associations of HZ knowledge with specific socio-demographic groups. Similar studies should also be conducted in younger adults.

Since 2014, the varicella zoster vaccine has been incorporated into the Hong Kong Childhood Immunisation Programme, under which children will be vaccinated against chickenpox at 1 year of age and during their first year of primary education.22 23 While this may offer protection against chickenpox and HZ for future generations, more studies are needed to determine whether it is also cost-effective to offer HZ vaccination to the population aged 50 years or above. This may have notable implications for its acceptance and practice.

Hong Kong people generally have some knowledge about the symptoms of HZ, and are aware that treatment is available for active disease. Nonetheless, there remains unsatisfactory understanding of the disease progression from chickenpox to HZ, and misconceptions about the disease remain prevalent, particularly in the older age-group. The lack of knowledge that HZ is preventable may be pertinent to the relatively low awareness and acceptance of the HZ vaccine compared with that for vaccines for other important diseases such as influenza and pneumococcal pneumonia. Further public education about varicella zoster and HZ, covering both disease features and effective prevention, will help to empower health, rectify misconceptions, and reduce disease burden in Hong Kong.

The authors would like to thank Dr Wendy WS Tsui and Dr Alfred SK Kwong from the Department of Family Medicine and Primary Health Care, Queen Mary Hospital, for their kind permission to conduct the study in the Sai Ying Pun GOPC. We thank Dr LW Tian from the Division of Epidemiology and Biostatistics, School of Public Health, the University of Hong Kong, for his invaluable feedback and support. This study was conducted by medical students as a Health Research Project submitted to the School of Public Health, Li Ka Shing Faculty of Medicine, the University of Hong Kong.

All authors have disclosed no conflicts of interest.

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