Coronavirus disease 2019 (COVID-19) has caused panic, impacted mental health, and disrupted healthcare systems worldwide [1-3]. The new COVID-19 variant (Delta) spreads rapidly with greater transmissibility [4]. By October, 2021, the Department of Medical Science confirmed that 76 out of 77 provinces in Thailand had recorded cases of COVID-19 with the Delta variant [5]. Over 10,000 new COVID-19 cases have been reported in Thailand since July, 2021, with an average of 100 deaths per day [6].

Many countries have promoted COVID-19 vaccination campaigns to contain the virus and attain the concept of herd immunity. Globally, 34% of the population has been fully vaccinated. In Thailand, however, this proportion is only 23% [7]. There is an urgent need to improve the public ability to detect fake news and promote health literacy of vaccine benefits against SARS-CoV-2 [8].

Health literacy reflects the capacity to gain access to, understand, and use health information in ways that promote and maintain good health [9]. However, gaining information regarding vaccines requires certain literacy skills. Previous studies developed and applied the concept of health literacy to create tools for vaccine literacy (VL) comprising functional, interactive, and critical elements. The validity and feasibility of a vaccine literacy tool were demonstrated by studies conducted in Italy and Croatia [10, 11].

Improved health literacy may increase vaccination acceptance (VA) [8]. However, the COVID-19 vaccines are developing at a very fast pace; therefore, some safety concerns still remain, resulting in vaccine hesitancy (VH) among the public [12]. Inevitably, another consequence of the COVID-19 pandemic is vaccine fear (VF).

Fear is a condition commonly associated with infectious diseases. Pappas et al. demonstrated a direct association between the speed and invisibility of disease transmission and its morbidity and mortality [13], while a study in Austria demonstrated that people also dread the consequences of vaccination [14]. Moreover, high levels of fear and anxiety may affect thinking processes and how to react to COVID-19 [13]. Several studies applied tools to assess the fear of COVID-19, while Ahorsu et al. developed a Fear of COVID-19 Scale [15-17].

In Thailand, village health volunteers (VHVs) are responsible for public COVID-19 control. These VHVs are hailed as “unsung heroes” by the World Health Organization (WHO) [18]. In 2021, when the first vaccines arrived in Thailand, the Thai prime minister encouraged village health volunteers to increase public trust in the COVID-19 vaccination program. Hence, there is a need to obtain and communicate vaccine information, especially by VHVs [19].

As aforementioned, it is necessary to estimate COVID-19 VL, VF, VH, and VA among VHVs at different times using separate tools. Such a study has never been performed in Thailand, especially regarding vaccine literacy.

This study developed and validated a comprehensive questionnaire as a tool to evaluate COVID-19 VL, VF, VH, and VA among 210 VHVs in Thailand.

Several studies have assessed fear, hesitancy, and acceptance of COVID-19 [12, 14-17], but none of the studies have evaluated vaccine literacy among VHVs, especially in Thailand. VHVs are important intermediate communicators between healthcare professionals and people that deliver health information directly to villages. During the COVID-19 pandemic, VHVs played an important role in screening, quarantine, and basic care, resulting in early detection and greater public knowledge by encouraging COVID-19 vaccination in Thai communities [22, 23]. Here, a questionnaire was developed to cover COVID-19 vaccine literacy, fear, hesitancy, and acceptance. To the best of our knowledge, this is the first study to evaluate COVID-19 vaccine literacy among VHVs in Thailand. The developed tool showed high validity and reliability for all items, with an overall Cronbach’s alpha value of 0.87. The study found high average scores for vaccine literacy, fear, and hesitancy but low acceptance scores.

The structured questionnaire also gave high validity and reliability at above 0.87 for all dimensions (literacy, fear, hesitancy, and acceptance), concurring with the findings of Biasio et al. and Gusar et al. [10, 11]. Biasio et al. developed a novel tool that examined VL, referred to as the Health Literacy Vaccinale degli adulti in Italiano (HLVA-it). They reported Cronbach’s alpha values for functional, interactive, and critical vaccine literacy as 0.8814, 0.9021, and 0.9369, respectively. Here, questions in the vaccine literacy section were based on the tool of Biasio et al., giving Cronbach’s alpha values of functional, interactive, and critical literacy as 0.860, 0.863, and 0.8570, respectively. This implied that the questionnaire was feasible for application in the Thai community. However, item loading of vaccine literacy favored by PCA gave a different result from Biasio et al. and Gusar et al.

The Italian study by Biasio et al. showed that interactive and critical vaccine literacy both had high loading on component 1, while functional vaccine literacy had higher loading on component 2 [10]. Similarly, the Croatian study by Gusar et al. showed that interactive and critical vaccine literacy were dominant in component 1, while functional vaccine literacy had high loading on component 2 [11]. In our study, functional and critical vaccine literacy had a higher contribution to component 1, while interactive vaccine literacy showed high loading on component 2 (Supplementary data Table S1). These different major loadings of items among the population suggested that vaccine literacy varied by population and country. Hence, vaccine literacy evaluation among a specific population was required.

The average literacy score among VHVs was over 2.5, similar to previous studies [10, 11, 24, 25]. The high literacy score possibly resulted from the examination of mostly healthy people with non-severe diseases. VHVs are not official healthcare professionals. Their duties include updating the public with the latest COVID-19 information during the vaccination campaign launched in late February, 2021 [(19)]. The prime minister of Thailand tasked the VHVs to boost acceptance of the COVID-19 vaccine in local Thai communities [26]. Our interactive VL scores were lower than the functional and critical scores. Cherif et al. used a cut-off value of 2.5 to classify high and low VL and found low VL in cancer patients in Tunisia [27]. Interactive VL scores in our study were higher than 2.5. Health literacy is a vital ability for accurately analyzing health information; higher levels of health literacy were linked to improved health status [16]. Health literacy and vaccine literacy both require individuals to assimilate the applicable information and make an informed vaccination decision [28]. The concept of vaccine literacy is similar to health literacy and is defined as “not simply knowledge about vaccines but also about developing a system with decreased complexity to communicate and offer vaccines as a sine qua of a functioning health system” [29, 30]. Furthermore, VL is also relevant to health promotion and can be defined as the process of empowering individuals to take care of their health [30, 31]. Therefore, vaccine literacy among VHVs focused on interactive skills that reflected the ability to interact with healthcare providers and interpret the information delivered to the public [31].

Different scores of VL, VF, VH, and VA were also examined by characteristic variables. Higher age had significantly better average VL scores. This finding was inconsistent with previous studies [11, 24]. Baker et al. concluded that functional vaccine health literacy declined with increasing age [31]. A possible explanation for our results was the study population of VHVs who had registered for the mobile applications “SMART Village Health Volunteer” and “Aor Sor Mor Online” that served many functions, including getting news, updating the COVID-19 pandemic situation, and supporting knowledge regarding COVID-19 prevention and vaccination. Users can also share advantageous information in the form of texts, images, audio, and video. VHVs work closely with community leaders, networks, and officers [32]. Therefore, all participants were able to access information. Our study recruited VHVs with a median age of 53 years (Q1: 46; Q3: 61). A previous study with a large sample size revealed that adults less than 69 years old showed a non-significant increased risk of health literacy decline compared to those aged 52 years old [33], concurring with our result of higher literacy among older age groups.

Fear of adverse effects from the COVID-19 vaccine is one of the major problems that obstruct vaccine uptake [34]. The average VF score was 2.68 out of a maximum of 4. A higher score means higher fear of the COVID-19 vaccine. Our VF score concurred with a study in Vietnam at 60% of the maximum score; however, the Vietnamese study focused on fear of SARS-CoV-2 rather than the vaccine [17]. This finding was similar to a study in Bangladesh by Hossain et al., who reported moderate to high fear levels, with a mean fear score of 18.53 out of 35 (S.D.=5.013) [35]. Fitzpatrick et al. examined the relationship between COVID-19 fear and social vulnerabilities as well as mental health repercussions in people in the United States. They found that respondents were fearful, with an average score of nearly 7 on a scale of 10 [36]. Several studies concluded that fear and stress caused insomnia and mental disorders [35-37]. Our fear scores significantly differed among age groups. People less than 40 years old were more fearful than those over 60, while some studies revealed that older adults had higher levels of fear than younger adults [35, 38, 39], and many indicated a decline in fear in older adults and argued that aging was a protective factor [40-43].

Vaccines available in Thailand (as of October, 2021) include the inactivated virus Sinovac (CoronaVac) (SV) and the adenoviral vector AstraZeneca (ChAdOx1nCoV-19), (AZ) [44]. Reports indicated that young people might suffer more from side effects than the elderly [45], concurring with our results of increased fear among younger people. Different fear scores were also found between employees and business owners. Employees were less fearful than business owners because most had welfare payments provided by their companies. The possibility of injection injury also resulted in fear and contributed to vaccine hesitancy [46].

The average VH in our study was 2.51 out of 5, with no significant differences in hesitancy scores among demographic variables. Vaccine hesitancy resulted from fear. A recent study determined three common reasons for vaccine hesitancy among Thai citizens, as stated by participants: “The vaccine can have dangerous side effects,” “I may be allergic to the vaccine,” and “The vaccine may not work” [47]. In our study, the three highest average scores of hesitancy were observed for “not sure about the efficacy of the Coronavac (Sinovac) vaccine,” “vaccination is the best way of preventing COVID-19,” and “do not trust the information provided by the government.” Therefore, to reduce the hesitancy of Thais, transparency in educating people about vaccine efficacy is needed. Concentrating efforts on implementing the abovementioned procedures will greatly assist in reducing COVID-19 vaccine hesitancy among VHVs in Thailand. This will considerably help to control the spread of the COVID-19 pandemic. Increased participation of local authorities, such as healthcare authorities, media, and regular authorities, including relevant research authorities, will aid COVID-19 control efforts of VHVs in Thailand.

Unsurprisingly, acceptance scores of the COVID-19 vaccine were low among VHVs. Studies in several countries revealed negative acceptance of COVID-19 vaccines [48] at greater than 30% of the overall population [49-51]. Vaccine acceptance varied depending on geographical location, with low acceptance in Kuwait (23.6%) and Jordan (28.4%) and moderate acceptance in Italy (53.7%), Poland (56.3%), and Russia (54.9%). In addition, the proportion of the participants accepting the use of a safe and effective COVID-19 vaccine was the highest in China at 88.6% [49]. One of the main reasons for these attitudes was doubts that the vaccines were safe [48-52]. Significantly different scores were recorded among age groups, marital status, and occupation. Older age groups had higher acceptance scores. This result concurred with a study in Thailand that demonstrated higher mean scores of acceptance in older adults (≥65 years) [47]. Higher COVID-19 vaccine acceptance among older adults was also found in several studies [53-56]. In Thailand, the two major vaccines are SV and AZ. The efficacy of SV has been questioned compared to mRNA vaccines [57], while younger people reported more side effects after taking a shot of AZ [46]. These reports contributed to higher acceptance scores among the elderly (>60 years). Cocktail vaccines were introduced nationwide in Thailand in July, 2021 [58]. However, the WHO warned that mixing vaccines from different manufacturers lacked conclusive evidence of strong immunity [59].

The association between COVID-19 vaccine literacy, fear, hesitancy, and acceptance was also investigated. Significantly negative associations were found between hesitancy and literacy, acceptance and fear, and age and fear. This implied that increasing VL reduced VH. Turhan et al. reported that people with low health literacy or difficulty accessing accurate information regarding COVID-19 vaccines had higher levels of vaccine hesitancy. Conversely, participants with less vaccine reluctance showed reduced vaccine hesitancy if they were able to access information concerning the decision-making on the merits of vaccination [60]. Minimizing fear increased vaccine acceptance. Many studies documented that intensifying COVID-19 immunization mobilization and delivering positive messages about vaccine efficacy reduced fear and boosted vaccine acceptability [54, 61]. There was a significant positive association between age and acceptance, similar to comparing the median difference of acceptance scores by age, as mentioned earlier. Therefore, the Thai government should pay attention to the young age group to boost vaccination uptake.

This study had limitations as follows. First, the sample population was not large enough to display significant results, but this was not the primary purpose. Results demonstrated the feasibility of an online survey using popular social platforms, such as Line and Facebook. Future studies should conduct surveys using a larger population via an online questionnaire. Second, this research was conducted during the fourth wave of COVID-19, and the vaccination campaign had already been launched in Thailand. Thus, the scores may not reflect vaccine literacy, fear, hesitancy, and acceptance at the start of the pandemic. Third, this research was performed on VHVs. This group of people operates as intermediate communicators between healthcare professionals and people in the community. Findings were, therefore, generalized to a particular segment of society.

The online structured questionnaire showed high validity, reliability, and feasibility among VHVs in Thailand. Based on the study, high average scores of literacy, fear, and hesitancy but low acceptance scores were found, with different scores of literacy, fear, and acceptance of COVID-19 recorded for age, marital status, and occupation. Some correlations were identified between the four dimensions of COVID-19. Further studies with larger sample sizes are needed to clarify the results of this assessment tool among VHVs in Thailand.