Research Knowledge, attitudes and beliefs about vaccination in primary healthcare workers involved in the administration of systematic childhood vaccines, Barcelona, 2016/17 Camila Andrea Picchio1,3,4 , Mireia Garcia Carrasco1,4 , Maria Sagué-Vilavella2,3,4 , Cristina Rius2,4,5 1. Servei Programes i Intervencions Preventives, Agencia de Salut Publica de Barcelona, Barcelona, Spain 2. Servei d’Epidemiologia, Agencia de Salut Publica de Barcelona, Barcelona, Spain 3. Universitat Pompeu Fabra, Barcelona, Spain 4. Universitat Autonoma de Barcelona, Barcelona, Spain 5. CIBER Epidemiología y Salud Pública (CIBERESP), Instituto Carlos III, Madrid, Spain Correspondence: Mireia Garcia Carrasco (mgcarras@aspb.cat) Citation style for this article: Picchio Camila Andrea, Carrasco Mireia Garcia, Sagué-Vilavella Maria, Rius Cristina. Knowledge, attitudes and beliefs about vaccination in primary healthcare workers involved in the administration of systematic childhood vaccines, Barcelona, 2016/17. Euro Surveill. 2019;24(6):pii=1800117. https://doi.org/10.2807/1560- 7917.ES.2019.24.6.1800117 Article submitted on 14 Mar 2018 / accepted on 17 Oct 2018 / published on 07 Feb 2019 Background: Healthcare professionals are a reliable paediatric nurses in PCC had vaccine doubts, espe- and impactful source of information on vaccination cially regarding the HPV vaccine. for parents and children. Objectives: We aimed to describe the knowledge, attitudes and beliefs pri- Introduction mary care professionals involved in administration of The term vaccine hesitancy (VH) was defined in 2012 childhood vaccines in Barcelona have about vaccines by the World Health Organization’s (WHO) Strategic and vaccination. Methods: In 2016/17, surveys were Advisory Group of Experts (SAGE) on Immunization as administered in person to every public primary care ‘delay in acceptance or refusal of vaccination despite centre (PCC) with a paediatrics department (n = 41). availability of vaccination services. Vaccine hesitancy Paediatricians and paediatric nurses responded to is complex and context specific, varying across time, questions about disease susceptibility, severity, place and vaccines. It is influenced by factors such as vaccine effectiveness, vaccine safety, confidence in complacency, convenience and confidence’ [1]. organisations, key immunisation beliefs, and how they vaccinate or would vaccinate their own children. During the last decade, groups or subpopulations where We used standard descriptive analysis to examine the vaccination coverage is below the required threshold distribution of key outcome and predictor variables because of VH have been associated with outbreaks and performed bivariate and multivariate analysis. and the reappearance of vaccine-preventable dis- Results: Completed surveys were returned by 277 eases, like measles [2]. In 2017, the WHO reported a (81%) of 342 eligible participants. A quarter of the total of 21,315 cases of measles and 35 deaths in the respondents reported doubts about at least one vac- European Region of the WHO alone, representing an cine in the recommended childhood vaccination cal- increase of 400% compared with the previous year [3]. endar. Those with vaccine doubts chose the response In Barcelona, however, the situation was more stable option ‘vaccine-hesitant’ for every single key vaccine despite 46 confirmed measles cases that originated belief, knowledge and social norm. Specific vaccine from imported cases in the same year [4,5]. knowledge was lacking in up to 40% of respondents and responses regarding the human papilloma virus Notwithstanding the impact of the media and the easy vaccine were associated with the highest degree of access to the Internet, which can contribute positively doubt. Being a nurse a risk factor for having vaccine or negatively [6] to the acceptance of childhood immu- doubts (adjusted odds ratio (ORa) = 2.0; 95% confi- nisation, healthcare professionals (HCPs) have repeat- dence interval (95% CI): 1.1–3.7) and having children edly been identified as the most reliable and impactful was a predictor of lower risk (ORa = 0.5; 95% CI: 0.2– source of information on vaccination for parents and 0.9). Conclusions: Despite high reported childhood their children [2,7-9]. Sixty-nine per cent of Spanish immunisation rates in Barcelona, paediatricians and families identified their paediatrician as the most www.eurosurveillance.org 1 Figure 1 Paediatric health professionals who responded ‘late’, ‘doubts’, or ‘no’ to vaccinating their own children, survey about vaccine knowledge, attitudes and beliefs, Barcelona, 2016/17 (n = 277) 20 Late Percentage of professionals with doubts "If you have or imagine you had a child, what vaccines No from the current recommended vaccination calendar 15 Doubts would you administer to them?" 10 5 0 s sC s b iru cu ae cu oc av nz oc oc m ue oc llo m nfl ng eu pi si pa Pn i en lu an M hi m op Hu em Vaccine Ha important source regarding vaccines [10]. Nonetheless, doctors or practitioners who specialise in fields not although it is internationally recommended [8] to work related to paediatrics and nurses who were not directly with this population to counter VH, HCPs in the region involved in the administration of childhood vaccines of Catalonia in Spain have not been studied. were excluded. Students, residents and temporary substitutes of any kind were also excluded. Given that VH has been described among European vaccine providers [11], it is of the utmost importance to Of the 54 PCC serving the city of Barcelona, 41 have a address the loss of confidence in vaccines in this pop- paediatrics department with overall 342 professionals. ulation. Entire vaccination programmes could be jeop- ardised if healthcare professionals’ recommendations Questionnaire to immunise children are deficient as a result of VH [7]. A questionnaire was developed following available lit- Faced with this situation at the European level, and in erature [12-14]. The questionnaire was translated into spite of adequate vaccine coverage, the Public Health Spanish and Catalan and culturally adapted using the Agency of Barcelona (ASPB) launched in 2016 a line of cognitive debriefing method [15]. Cognitive debriefing research to monitor VH in HCPs and study its determi- is a process where representatives of the target popu- nants in Barcelona. The main objective of this study lation actively test the translated questionnaires to was to describe the knowledge, attitudes and beliefs determine whether respondents would understand the about vaccines among professionals who are directly questionnaire as easily as the English version would be involved in the administration of systematic childhood understood [16]. vaccines in the public health system of the city. Respondents answered questions about disease sus- Methods ceptibility, disease severity, vaccine effectiveness, This investigation is an observational cross-sectional vaccine safety, who benefits from childhood immuni- study consisting of data collected through a structured sations, key immunisation beliefs, whether or not they survey. had children, how they vaccinated or would vaccinate their own children, and whether they felt they had Population surveyed enough information and tools in order to adequately In Barcelona, systematic childhood vaccination is rec- respond to vaccine-hesitant parents. ommended and administered by paediatric health professionals (paediatricians and paediatric nurses). Administration The public health system covers more than 90% of all Questionnaires were self-administered by the HCPs at childhood vaccinations in the city. The study popula- the PCC during a date and time that was previously tion enrolled were HCPs who were directly involved in agreed between the investigators and contact person the administration of systematic childhood vaccines in from each centre. Contact with centres began in March public primary care centres (PCC) in Barcelona. Family 2 www.eurosurveillance.org Figure 2 Disease susceptibility and severity perceived by paediatric health professionals, survey about vaccine knowledge, attitudes and beliefs, Barcelona, 2016/17 (n = 277) "What probability do you consider that an unvaccinated or unimmunised child has of contracting the following illnesses? Consider a 10-year period in the current Spanish context." Polio Meningococcus C Diphtheria Hepatitis B Haemophilus influenzae b Rubella Vaccine Measles Tetanus Hepatitis A Parotitis Pneumococcus Human papillomavirus Whooping cough Varicella 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% % responses Impossible Unlikely Neither probable nor improbable Probable Very probable DK/NR "How severe do you consider it to be for an unimmunised and unvaccinated 8-year-old to become ill with the following diseases?" Varicella Parotitis Hepatitis A Rubella Measles Vaccine Whooping cough Haemophilus influenzae b Hepatitis B Pneumococcus Diphtheria Tetanus Polio Meningococcus C 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% % responses Not at all severe Not severe Somewhat severe Severe Very severe DK/NR DK/NR: don’t know/no response. www.eurosurveillance.org 3 Figure 3 Vaccine safety and effectiveness perceived by paediatric health professionals, survey about vaccine knowledge, attitudes and beliefs, Barcelona, 2016/17 (n = 277) "How safe do you consider the following vaccines?" Pneumococcus Rubella Haemophilus influenzae b Hepatitis B Diphtheria Tetanus Vaccine Polio Meningococcus C Hepatitis A Measles Parotitis Whooping cough Varicella Human papillomavirus 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% % responses Dangerous Unsafe Safe Very safe Totally safe DK/NR "What degree of protection do you believe the following vaccines offer?" Tetanus Polio Diphtheria Meningococcus C Hepatitis A Haemophilus influenzae b Vaccine Rubella Hepatitis B Pneumococcus Measles Parotitis Varicella Human papillomavirus Whooping cough 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% % responses No protection Little protection Some protection Protects Protects a lot DK/NR DK/NR: don’t know/no response. 4 www.eurosurveillance.org Figure 4 Key beliefs, knowledge and social norms about vaccines, by affirmation, survey among paediatric health professionals, Barcelona, 2016/17 (n = 277) SOCIAL NORMS The people in my immediate environment are in favour of vaccination Having an egg allergy is a contraindication for the MMR vaccine The amount of aluminium in vaccines can cause neurotoxicity KNOWLEDGE At least one vaccination in the vaccination calendar contains aluminium The amount of thiomersal in vaccines can cause neurotoxicity At least one vaccination in the vaccination calendar contains thiomersal The varicella vaccine can be a cause of attenuated varicella The MMR vaccine can be a cause of autism I believe that the vaccines in the current vaccination calendar are influenced by illegitimate pharmaceutical interests I believe that the vaccines in the current vaccination calendar are influenced by illegitimate governmental interests I believe that at least one of the vaccines in the current vaccination calendar is administered too early Continuing to vaccinate children against polio in Spain is acceptable, even though it has been eliminated from the country It is better for children to develop immunity by having the illness than BELIEFS through vaccination Vaccines strengthen the immune system Thanks to scientific research, vaccines are increasingly better and effective Vaccines are one of the safest sanitary measures that exist I am more likely to trust vaccines that have been around longer, compared with newer vaccines It worries me that the immune systems of children could be weakened by receiving an excess amount of vaccines Children receive more vaccines than they need Children should only be vaccinated for serious illnesses 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% % responses Non-vaccine-hesitant option Vaccine-hesitant option Missing values MMR: measles-mumps-rubella vaccine. Responses to key vaccine knowledge, beliefs and social norms were categorised as either vaccine-hesitant or non-vaccine hesitant. www.eurosurveillance.org 5 2016 and ended in February 2017. Some centres were Of those that were surveyed, 71 (25.6%; 95% CI: 20.8– contacted up to six times. 31.1) had doubts about at least one of the vaccines in the current vaccination calendar. Respondents reported Variables the most doubt regarding the HPV and varicella vac- Demographical variables were collected. All other varia- cines (Figure 1, Supplementary Table S1). Excluding the ble responses were categorised on a 5-point Likert scale HPV and varicella vaccines, 34 (12.3%; 95% CI: 8.8– that was later dichotomised. Responses to whether or 16.7) of health professionals reported having a doubt not they would vaccinate their children against the about at least one vaccine in the current calendar. listed vaccines included in the calendar were dichot- omised into ‘yes’ and the outcome variable ‘vaccine Statistically significant differences existed between doubts’ which was a combination of all other options professions for the pneumococcus (3.8% vs 9.9%; (late/doubts/no). Disease susceptibility and severity p = 0.049), Hepatitis B (1.5% vs 7.6%; p = 0.034) and variables were dichotomised into ‘likely/very likely’ HPV (9.9% vs 22.9%; p = 0.005) vaccines where nurses vs all other responses and ‘severe/very severe’ vs all reported more doubts. Statistically significant differ- other responses. Vaccine safety was dichotomised into ences existed between those with and without children ‘safe/very safe/completely safe’ vs all other responses for the varicella vaccine (12.5% vs 25.4%; p = 0.012) and vaccine efficacy was dichotomised into ‘protects/ where those without children reported more doubts. protects a lot’ vs all other responses. Benefit of vacci- nation was dichotomised into benefits ‘considerably/a Perception of probability and severity of illness lot’ vs all other responses. Key vaccine beliefs, knowl- and of vaccine safety and protection edge and social norms were also dichotomised into Thirteen (4.7%) respondents felt that it would be the ‘vaccine-hesitant’ option vs no VH. Because the impossible for an unvaccinated and unimmunised child key affirmations were positive and negative, agreeing to contract polio and 198 (71.5%) responded that it is with the affirmation was the vaccine-hesitant option in probable or very probable for an unvaccinated child some cases, while in others, disagreeing corresponded to contract HPV. Respondents reported that polio, ill- to VH. Missing values and don’t know/no response ness from meningococcus C and tetanus were the most (DK/NR) were all treated the same in the analysis. serious illnesses, with varicella being the least serious (Figure 2, Supplementary Tables S2 and S3). All vac- Data analysis cines were reported to be safe, with the exception of Standard descriptive statistics was performed using the HPV vaccine, which was described as dangerous by STATA version 11.0. Mean, standard deviation and one participant and unsafe by 14 (5%). Five respond- Student’s t-test were used for quantitative variables ents also reported the varicella and whooping cough and frequency, chi-squared test, and Fisher’s exact vaccines as being unsafe (Figure 3, Supplementary test were used for qualitative variables. To study soci- Tables S4 and S5). We saw the largest number of miss- odemographic correlates with VH, a multiple logistic ing values for questions surrounding HPV. Eighteen regression was performed where odds ratios (OR) were missing values (6.5%) were received for HPV suscepti- obtained with their 95% confidence intervals (95% CI), bility, 23 (8.3%) for HPV vaccine safety and 29 (10.5%) adjusting for all sociodemographic variables. Missing for the level of protection the vaccine provides. In gen- values and DK/NR were included only in the descrip- eral, there were no statistically significant differences tive analysis. All analyses were based on two-sided p in sex, age or years of profession in relation to the vari- values with statistical significance defined by p ≤ 0.05. ables on probability and severity of illness and on the protection offered by vaccines. Statistically significant Ethical considerations differences were seen among those without children This study was approved by the ethics committee of the who reported more doubts regarding the safety of the Consorci Parc de Salut Mar de Barcelona. The research- HPV vaccine (11.5% vs 3%; p = 0.019). Statistically sig- ers declare no conflicts of interest. nificant differences between professions were seen in almost every category. Results Of the 342 paediatric health professionals in the Key vaccine beliefs, knowledge and social Barcelona public primary care centres, 277 (81%) par- norms ticipated in the study; 136 were paediatricians, 138 Of the 277 who participated, 269 (97.1%) believed that were paediatric nurses and three were not defined. The the child receiving the vaccine benefits considerably/ rate of participation of paediatricians and paediatric benefits a lot from vaccination, 267 (96.4%) believed nurses was 76.8% and 83.6%, respectively. Only one that the community benefits considerably/benefits a PCC chose not to participate. The mean age was 48 lot, 256 (92.4%) believed that health personnel ben- years (SD = 10.5 years) and 244 (88.4%) were female. efit considerably/benefit a lot, 253 (91.3%) believed The mean number of years of experience was 23 years that the government benefits considerably/benefits a (SD = 10.5 years). Of those who responded to the sur- lot, and 244 (88.1%) believed that the pharmaceutical vey, 75 (27.1%) reported not having children. industry benefits considerably/benefits a lot. There were no significant differences regarding the responses to beliefs about the benefits of vaccination. 6 www.eurosurveillance.org Table Respondents with or without doubts about vaccines who selected the vaccine-hesitant option, survey among paediatric health professionals, Barcelona, 2016/17 (n = 277) Respondents without Respondents with doubts doubts (n = 71) a p value (n = 206)a n % n % Children should only be vaccinated for serious illnesses 36 53.7 35 17.50 < 0.001 Children receive more vaccines than they need 33 47.1 24 11.94 < 0.001 It worries me that the immune systems of children could be weakened by 19 27.9 17 8.46 < 0.001 receiving an excess amount of vaccines I am more likely to trust vaccines that have been around longer, 33 47.1 66 32.67 0.030 compared with newer vaccines Vaccines are one of the safest sanitary measures that exist 10 14.5 13 6.44 0.038 Thanks to scientific research, vaccines are increasingly better and 10 14.5 11 5.45 0.015 effective Vaccines strengthen the immune system 23 34.3 33 17.19 0.003 It is better for children to develop immunity by having the illness than 24 36.3 25 12.76 < 0.001 through vaccination Continuing to vaccinate children against polio in Spain is acceptable, 7 10.0 9 4.59 0.102 even though it has been eliminated from the country I believe that at least one of the vaccines in the current vaccination 36 54.5 49 24.75 < 0.001 calendar is administered too early I believe that the vaccines in the current vaccination calendar are 40 59.7 84 44.21 0.029 influenced by illegitimate governmental interests I believe that the vaccines in the current vaccination calendar are 46 68.6 91 48.40 0.004 influenced by illegitimate pharmaceutical interests The MMR vaccine can be a cause of autism 7 10.9 9 4.57 0.065 The varicella vaccine can be a cause of attenuated varicella 35 52.2 96 48.73 0.620 At least one vaccine in the vaccination calendar contains thiomersal 28 70.0 65 46.43 0.009 The amount of thiomersal in vaccines can cause neurotoxicity 17 37.7 49 32.24 0.489 At least one vaccine in the vaccination calendar contains aluminium 40 74.0 106 67.95 0.399 The amount of aluminium in vaccines can cause neurotoxicity 18 31.5 46 28.75 0.688 Having an egg allergy is a contraindication for the MMR vaccine 12 17.6 27 13.57 0.411 The people in my immediate environment are in favour of vaccination 6 8.4 3 1.50 0.011 MMR: measles-mumps-rubella. a Missing values were excluded. Of the 229 participants who believed that pharmaceu- Key vaccine knowledge affirmations showed the high- tical companies benefit considerably/benefit a lot from est number of missing values, and a higher percent- vaccination and responded to the question about ille- age of respondents chose the VH option. A total of gitimate interests influencing the vaccination calendar, 133 (48.0%) respondents correctly responded that the 129 (56.3%) believed that the vaccines currently rec- varicella vaccine can cause attenuated varicella. With ommended are influenced by illegitimate pharmaceuti- respect to the components that make up our vaccines cal interests compared with 100 (43.7%) who did not today, 93 participants (33.5%) responded that at least believe this (p = 0.012). one vaccine in the current vaccination calendar con- tains thiomersal and 97 (35%) did not know the answer Twenty-five (12.8%) participants who reported having or chose not to respond. Further, 80 respondents children felt worried that children’s immune systems (28.9%) did not know or chose not to answer the ques- could be weakened from receiving too many vaccines, tion which stated that the amount of thiomersal in vac- and 65 (33%) of these same respondents believed that cines can cause neurotoxicity. In addition, 67 (24.2%) at least one vaccine in the current calendar is admin- did not respond or did not know whether or not vac- istered too early. A total of 262 (94.6%) participants cines contain traces of aluminium, and 60 (21.7%) did reported that the people in their immediate environ- not know whether or not the amount of aluminium in ment were in favour of vaccination and 10 (3.6%) vaccines causes neurotoxicity (Figure 4). participants did not believe that thanks to scientific research, vaccines are increasingly better and more Those with vaccine doubts chose the VH response effective (Figure 4). option for every single key vaccine belief, knowledge www.eurosurveillance.org 7 and social norm (Table). Of those who had doubts about alarming that some health professionals considered at least one vaccine in the current vaccination calen- vaccines that are being administered to children as dar, 60% responded that they believed that the current unsafe or even dangerous. The large number of missing vaccines in the calendar were influenced by illegitimate responses associated with the HPV vaccine indicates governmental interests (p = 0.029). Similarly, of those a sense of doubt or unawareness about this vaccine’s who had vaccine doubts, 69% reported believing that proven safety and efficacy. Karafillakis et al. also the current vaccination calendar was influenced by ille- described that the HPV vaccine was singled out in their gitimate pharmaceutical interests (p = 0.004). recent study and explain the hesitancy by the fact that it is a new vaccine [19]. Multivariate analysis adjusted for sociodemographic characteristics revealed the profession of nursing to Doubts surrounding the vaccine which protects young be a risk factor for VH (ORa = 2.0; 95% CI: 1.1–3.7) girls from HPV is in line with the opinions of certain and having children as a factor of less risk for VH groups [23], but indicating that the varicella, whooping (ORa = 0.5; 95% CI: 0.2–0.9). cough and mumps vaccines are also unsafe, potentially indicates an inability to differentiate between vaccine Professional practice and vaccine doubts safety and effectiveness, a crucial determinant when Overall, 81 (29.2%) of the 277 HCPs responded that educating vaccine-hesitant parents. they felt they did not have sufficient information and training to adequately answer questions vaccine-hes- Our respondents’ perceptions of disease severity and itant parents may have. The majority of respondents probability were almost identical to those reported by wished to receive more information about vaccines Salmon et al. [12]. In our study, however, the perception online 145 (52.3%) and through training sessions 139 of probability of infection varied. Some professionals (50.2%). considered polio virus infection virtually impossible, an opinion that may have consequences. For example, Discussion overconfidence in the safety and effectiveness of a vac- Our study showed that, in general, public paediat- cine such as the one against polio, a disease assumed ric professionals in Barcelona supported vaccination. to be eliminated in our environment, could prevent an However, one in four respondents reported having HCP from recommending the vaccine to families who doubts about at least one vaccine in the current rec- have doubts about it. ommended childhood vaccination schedule. Half of the doubts expressed were described in association with We interpret the high rate of missing values and DK/ the HPV and varicella vaccines. Moreover, we identi- NR in our study as a gap in specific key vaccine knowl- fied a lack of trust in the government and the pharma- edge. Hence, the conclusion can be drawn that HCPs ceutical industry, a lack of knowledge about vaccine administering vaccines to children in the public health components and the belief in certain myths held by system in Barcelona are lacking crucial information vaccine-hesitant parents. about vaccine components, contraindications and critical general vaccine knowledge. Paterson et al. Despite recent attempts in Spain to unify childhood described that overall, knowledge about particular vaccination schedules, different ones coexist: one for vaccines, their efficacy and their safety helped build each autonomous region. The Catalan recommended healthcare professionals’ own confidence in vaccines vaccination calendar has been changed four times in and their willingness to recommend them to others [9]. the past 10 years [17]. The two vaccines which gener- Improving vaccine knowledge among these profession- ated the most doubt in our study population were only als is crucial for guiding vaccine-hesitant parents and recently added to the recommended systematic child- recommending vaccination. hood vaccination calendar (HPV in 2008 and varicella in 2016), and their introduction was accompanied by The frequency of vaccine misconceptions in our study social and scientific criticism. The doubts surround- was similar to the study by Salmon et al. [12]. A large ing these vaccines described in our population can in number of participants chose the VH response and did part be explained by the frequent changes in the vac- not answer questions related to myths that vaccine- cination calendar and differing calendars within the hesitant parents might ask. Myths could become part country [18]. This lack of confidence in certain vaccines of the belief structure of a society and our results sug- could be highlighting the need to improve communica- gest that the environment has already influenced the tion between those who dictate public health policies surveyed professionals in the same way as it does and health professionals who directly care for families. vaccine-hesitant families. Addressing this aspect Karafillakis et al. described similar scenarios in France would require working within the socio-cultural context and Greece where a lack of trust in the government and as suggested by Yaqub et al. [2]. These investigators pharmaceutical industry could potentially stain the warned of the risks of focusing only on vaccine uptake credibility of vaccine information [19]. rates and overlooking the underlying attitudes and beliefs associated with VH. While the vaccine effectiveness responses we received were in line with available literature [20-22], it is 8 www.eurosurveillance.org Authors’ contributions One third of those surveyed felt that they do not have sufficient information and training to adequately MSV, MGC and CR created the questionnaire that was admin- address questions from vaccine-hesitant parents. We istered. MGC contacted each centre to set up a time and date and MGC, MSV, CR and CAP travelled to each centre to ad- must ensure that health professionals who are in con- minister the questionnaires. Data analysis was performed by tact with families are adequately informed and are CAP using STATA. CAP, MGC and CR actively participated in capable of delivering clear and accurate messages to discussion of results and key ideas for the article, and wrote their patients [18,24]. To this effect, new and improved and edited the article. training workshops and information material need to be made available as continued education to these healthcare professionals as soon as possible. References 1. MacDonald NESAGE Working Group on Vaccine Hesitancy. Vaccine hesitancy: Definition, scope and determinants. Our results must be interpreted in the context of several Vaccine. 2015;33(34):4161-4. https://doi.org/10.1016/j. methodological limitations. While the high response vaccine.2015.04.036 PMID: 25896383 rate is a strength of this study, it can also be seen 2. Yaqub O, Castle-Clarke S, Sevdalis N, Chataway J. Attitudes to vaccination: a critical review. Soc Sci Med. 2014;112:1- as a drawback. 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