Have preferences of girls changed almost 3 years after the much debated start of the HPV vaccination program in The Netherlands? A discrete choice experiment

The application of discrete choice experiments eliciting young peoples' preferences for healthcare: a systematic literature review

OBJECTIVES

Understanding young people's preferences for healthcare is critical for reducing the negative effect of undesirable choices. This review aims to synthesise the evidence obtained from discrete choice experiments (DCEs) eliciting young people's preferences for healthcare interventions and service deliveries, specifically, to (1) examine the methodology, including a selection of attributes and levels, experimental design, estimation procedure and validity; (2) evaluate similarities, differences and rigour of designs to the general population DCEs; and, (3) compare the DCEs' application to the seven health priority areas defined by the World Health Organisation (WHO).

METHODS

A systematic review searching Medline, EconLIT, PsychINFO, Scopus, and Web of Science was performed up until May 2021.

INCLUSION CRITERIA

a DCE, eliciting young peoples' preferences (10-24 years of age), on a healthcare-related topic defined by WHO, peer-reviewed, full-text available in English. A bespoke checklist was used to assess the methodological quality of the included studies.

RESULTS

Eighteen DCE studies were included in the review, exploring interventions and service in sexual and reproductive health (n = 9; 50%), smoking cessation (n = 4; 22%), mental health (n = 1), nutrition (n = 1), unintentional injuries (n = 1), vaccination against severe but rare diseases (n = 1); and diabetes (n = 1). Compared to the general population, DCEs eliciting young people's preferences had a high proportion of monetary measures and a smaller number of choices per respondent with the overwhelming number of surveys using fractional factorial design. The majority of studies were of moderate quality (50-75% of the criteria met).

CONCLUSIONS

While identified DCEs touched on most health priority areas, the scope was limited. The conduct and reporting of DCEs with young people could be improved by including the state-of-the-art design, estimation procedures and analysis.

Vaccine eagerness: A new framework to analyse preferences in single profile discrete choice experiments. Application to HPV vaccination decisions among French adolescents

Background

We previously conducted a single-profile discrete choice experiment to elicit preferences of adolescents around HPV vaccine communication, finding that only half of participants made variable choices (non-uniform respondents) from which preferences were elicited. In this paper we provide a framework to evaluate post-choice certainty information to elicit preferences even among respondents who uniformly accepted (serial demanders) or refused (serial non-demanders) hypothetical vaccination scenarios.

Methods

During an in-class online questionnaire among 1458 French adolescents aged 13–15 years old, we collected certainty levels (0–10) after decisions on nine hypothetical scenarios, including four vaccination attributes: information on vaccine-preventable disease type, on vaccine safety, on potential for indirect protection and on vaccine coverage. We developed a vaccine eagerness scale (ranging from −10 to 10), by combining information on the binary decision (accept vs. refuse the hypothetical vaccine) and the decision certainty level. We used random effects linear regressions to evaluate attributes’ impact on vaccine eagerness. Sensitivity analyses were performed taking into account low response quality, assessed as invariant certainty and low response time.

Results

Attributes’ impact on decision certainty were similar between serial demanders (N = 659) and non-uniform respondents (N = 711): mentioning a positive benefit-risk balance significantly decreased certainty to accept (coefficient −0.93), while information on 80% coverage in other countries (+0.33) and potential for disease elimination (+0.09) increased it. Among serial non-demanders, significant attribute impacts were observed only after exclusion of low-quality responses (N = 31): a potential for disease elimination (coefficient: +0.24) and 80% coverage in other countries (+0.42) significantly increased certainty of refusing vaccination. Combining decision and certainty into a vaccine eagerness indicator allowed analysing preferences in the full sample, including “hesitant” respondents, who were sensitive to the content of the vaccination profile.

Conclusion

Choice certainty informs on respondents’ preferences in single-profile discrete-choice experiments, in particular among those with uniform responses.

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Preferences are not identified among “uniform respondents” in single profile DCEs.

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Analysis of post-choice certainty can reveal information on their preferences.

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We propose a new concept for DCEs on vaccination, “vaccine eagerness”.

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Vaccine eagerness allows analyzing preferences among serial non-demanders.

Vaccine preferences driving vaccine-decision making of different target groups: a systematic review of choice-based experiments

BACKGROUND

Choice-based experiments have been increasingly used to elicit preferences for vaccines and vaccination programs. This study aims to systematically identify and examine choice-based experiments assessing (differences in) vaccine preferences of vaccinees, representatives and health advisors.

METHODS

Five electronic databases were searched on choice-based conjoint analysis studies or discrete choice experiments capturing vaccine preferences of children, adolescents, parents, adults and healthcare professionals for attributes of vaccines or vaccine settings up to September 2020. Data was extracted using a standardized form covering all important aspects of choice experiments. A quality assessment was used to assess the validity of studies. Attributes were categorized into outcome, process, cost and other. The importance of attributes was assessed by the frequency of reporting and statistical significance. Results were compared between high-quality studies and lower-quality studies.

RESULTS

A total of 42 studies were included, with the majority conducted in high-income countries after 2010 (resp. n = 34 and n = 37). Preferences of representatives were studied in nearly half of the studies (47.6%), followed by vaccinees (35.7%) and health advisors (9.5%). Sixteen high-quality studies passed the quality assessment. Outcome- and cost- related attributes such as vaccine effectiveness, vaccine risk, cost and protection duration were most often statistically significant across both target groups, with vaccine effectiveness being the most important. Risks associated with vaccination, such as side effects, were more often statistically significant in studies targeting vaccinees, while cost-related attributes were more often statistically significant in studies of representatives. Process-related attributes such as vaccine accessibility and time were least important across both target groups.

CONCLUSION

To our knowledge, this is the first systematic review in which vaccine preferences of different target groups were assessed and compared. The same attributes were most important for vaccine decisions of vaccinees and representatives, with only minor differences in level of evidence for vaccine risk and cost. Future research on vaccine preferences of health advisors and/or among target groups in low-resource settings would give insight into the generalizability of current findings.

Preference and willingness to pay of female college students for human papillomavirus vaccination in Zhejiang Province, China: A discrete choice experiment

The study aimed to quantify the preferences of female college students for human papillomavirus (HPV) vaccination in Zhejiang Province, China, using a discrete choice experiment (DCE). One medical college and one nonmedical college were selected using convenience sampling, and the respondents were identified using stratified cluster sampling. A DCE focused on vaccine-related and service-related attributes was conducted in 2019. Latent class analysis was used to estimate the vaccine-related attributes, and conditional logistic regression was used to construct the choice model for the service-related attributes. In total, 850 female college students finished the study. Two latent classes were identified. Those who had more knowledge of HPV and felt more pressure about the related infection and diseases had a significantly higher chance of belonging to class 1 and were more likely to choose vaccination (percentages of respondents choosing no vaccination was 1.1% in class 1 versus 84.7% in class 2, χ² = 641.1, P < .01). There were 742 respondents who chose vaccination in vaccine-related scenes, and 98.8% of them still chose to receive the vaccine in service-related scenes. Ways of making an appointment, number of weeks waiting for vaccination, service time for vaccination, time to the nearest vaccination site, and added cost all impacted the probability of choosing HPV vaccination services. It is concluded that higher levels of HPV knowledge and sociopsychological pressure led to a higher probability of HPV vaccination uptake in China. It is necessary to disseminate proper knowledge of HPV to improve the coverage and equality of HPV vaccination.

Mothers' preferences and willingness-to-pay for human papillomavirus vaccines in Iran: A discrete choice experiment study

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The relative importance for serious side effects was the highest among all attributes.

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Mothers express more WTP for the quadrivalent vaccine compared to bivalent due to its protection against genital warts.

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Quadrivalent vaccination could be the most suitable candidate for implementation in the national immunization schedule.

This study aimed to identify mothers’ preferences and willingness-to-pay (WTP) for human papillomavirus (HPV) vaccines (in this case, bivalent and quadrivalent) in Iran. We used a discrete choice experiment (DCE) method to present mothers with choices between two hypothetical profiles of vaccines, described by combinations of five attributes, each with two or three levels. We analyzed the DCE results using conditional logistic regression and measured WTP estimates for each attribute. Our response rate was 53.96%, while the completion rate for questioner was 93.57%. We identified protection against cervical cancer, protection against genital warts, protection duration, serious side effects, and cost to influence mothers’ preferences for HPV vaccination. The relative importance for serious side effects was the highest among all attributes. Mothers’ WTP for bivalent and quadrivalent HPV vaccines was in US $ −432 (US $1 = IRR 42,000) and US $ 380, respectively. Quadrivalent vaccination could be the most suitable candidate for implementing the national immunization schedule. The reason is that mothers express more WTP for the quadrivalent vaccine than bivalent due to its protection against genital warts.

Optimising HPV vaccination communication to adolescents: A discrete choice experiment

BACKGROUND

Human Papillomavirus (HPV) vaccine coverage in France is below 30%, despite proven effectiveness against HPV infections and (pre-)cancerous cervical lesions. To optimise vaccine promotion among adolescents, we used a discrete choice experiment (DCE) to identify optimal statements regarding a vaccination programme, including vaccine characteristics.

METHODS

Girls and boys enrolled in the last two years of five middle schools in three French regions (aged 13-15 years) participated in an in-class cross-sectional self-administered internet-based study. In ten hypothetical scenarios, participants decided for or against signing up for a school-based vaccination campaign against an unnamed disease. Scenarios included different levels of four attributes: the type of vaccine-preventable disease, communication on vaccine safety, potential for indirect protection, and information on vaccine uptake among peers. One scenario was repeated with an added mention of sexual transmission.

RESULTS

The 1,458 participating adolescents (estimated response rate: 89.4%) theoretically accepted vaccination in 80.1% of scenarios. All attributes significantly impacted theoretical vaccine acceptance. Compared to a febrile respiratory disease, protection against cancer was motivating (odds ratio (OR) 1.29 [95%-CI 1.09-1.52]), but not against genital warts (OR 0.91 [0.78-1.06]). Compared to risk negation ("vaccine does not provoke serious side effects"), a reference to a positive benefit-risk balance despite a confirmed side effect was strongly dissuasive (OR 0.30 [0.24-0.36]), while reference to ongoing international pharmacovigilance without any scientifically confirmed effect was not significantly dissuasive (OR 0.86 [0.71-1.04]). The potential for indirect protection motivated acceptance among girls but not boys (potential for eliminating the disease compared to no indirect protection, OR 1.57 [1.25-1.96]). Compared to mentioning "insufficient coverage", reporting that ">80% of young people in other countries got vaccinated" motivated vaccine acceptance (OR 1.94 [1.61-2.35]). The notion of sexual transmission did not influence acceptance.

CONCLUSION

HPV vaccine communication to adolescents can be tailored to optimise the impact of promotion efforts.

Methods for Conducting Stated Preference Research with Children and Adolescents in Health: A Scoping Review of the Application of Discrete Choice Experiments

BACKGROUND

Discrete choice experiments (DCEs) are a common method used to describe and quantitatively assess preferences in health applications. Increasingly, DCEs have been used to elicit preferences from children and adolescents and generate evidence to inform policies affecting this population.

OBJECTIVES

The aim of this review was to summarize and describe the application of DCEs conducted with children and adolescents and describe author-reported age-specific considerations in design, implementation, and analysis.

METHODS

A scoping review was conducted using a 'pearl-growing' technique whereby the reference lists of existing systematic reviews of DCEs were used to identify potential studies conducted with children or adolescents as respondents published between 1990 and 2017. This list was supplemented with an updated electronic search using the same strategy as the initial reviews to identify studies from 2017 to 2020.

RESULTS

Of 480 studies identified, 19 were included; topics included vaccines (32%), drugs/medical devices (26%), treatment or health promotion interventions/programs (21%), warning labels on cigarettes/nicotine products (10%), and preferences for physical activity and healthy food choices (10%). The youngest reported age for independent DCE completion was 8 years. Approaches to assessing validity and reliability of choices were consistent with best practices for the conduct of DCEs. Reported age-specific considerations included use of visual aids, age-appropriate language, reducing task complexity and cognitive burden, and exploration of interpretation of willingness-to-pay.

CONCLUSION

The number of DCEs conducted with children and adolescents has increased in recent years. Detailed explanation of why reported age-specific considerations were necessary, how they could be used to interpret results, or to understand the appropriateness of this methodology for different age groups was limited. Despite a recognition of the need for special consideration when conducting DCEs in this population, the unique issues in the context of age-specific considerations are largely unexplored, and further research is required. Moving forward, stated preference research conducted with children and adolescents should report in more detail methods of recruitment, results of validity assessments, and provide specific reflection on the extent to which modeled results are consistent with expectations and underlying theory.

Preferences for a COVID-19 vaccine in Australia

In absence of a COVID-19 vaccine, testing, contact tracing and social restrictions are among the most powerful strategies adopted around the world to slow down the spread of the pandemic. Citizens of most countries are suffering major physical, psychological and economic distress. At this stage, a safe and effective COVID-19 vaccine is the most sustainable option to manage the current pandemic. However, vaccine hesitancy by even a small subset of the population can undermine the success of this strategy.

The objective of this research is to investigate the vaccine characteristics that matter the most to Australian citizens and to explore the potential uptake of a COVID-19 vaccine in Australia. Through a stated preference experiment, preferences towards a COVID-19 vaccine of 2136 residents of the Australian states and territories were collected and analysed via a latent class model.

Results show that preferences for mild adverse cases, mode of administration, location of administration, price and effectiveness are heterogeneous. Conversely, preferences for immediacy and severe reactions are homogeneous, with respondents preferring a shorter period until vaccine is available and lower instances of severe side effects. The expected uptake of the vaccine is estimated under three different scenarios, with the value of 86% obtained for an average scenario. By calculating individual preferences, the willingness to pay is estimated for immediacy, effectiveness, mild and severe side effects.

Respondent Understanding in Discrete Choice Experiments: A Scoping Review

Introduction

Despite the recognised importance of participant understanding for valid and reliable discrete choice experiment (DCE) results, there has been limited assessment of whether, and how, people understand DCEs, and how ‘understanding’ is conceptualised in DCEs applied to a health context.

Objectives

Our aim was to identify how participant understanding is conceptualised in the DCE literature in a health context. Our research questions addressed how participant understanding is defined, measured, and used.

Methods

Searches were conducted (June 2019) in the MEDLINE, EMBASE, PsychINFO and Econlit databases, as well as hand searching. Search terms were based on previous DCE systematic reviews, with additional understanding keywords used in a proximity-based search strategy. Eligible studies were peer-reviewed journal articles in the field of health, related to DCE or best-worst scaling type 3 (BWS3) studies, and reporting some consideration or assessment of participant understanding. A descriptive analytical approach was used to chart relevant data from each study, including publication year, country, clinical area, subject group, sample size, study design, numbers of attributes, levels and choice sets, definition of understanding, how understanding was tested, results of the understanding tests, and how the information about understanding was used. Each study was categorised based on how understanding was conceptualised and used within the study.

Results

Of 306 potentially eligible articles identified, 31 were excluded based on titles and abstracts, and 200 were excluded on full-text review, resulting in 75 included studies. Three categories of study were identified: applied DCEs (n = 52), pretesting studies (n = 7) and studies of understanding (n = 16). Typically, understanding was defined in relation to either the choice context, such as attribute terminology, or the concept of choosing. Very few studies considered respondents’ engagement as a component of understanding. Understanding was measured primarily through qualitative pretesting, rationality or validity tests included in the survey, and participant self-report, however reporting and use of the results of these methods was inconsistent.

Conclusions

Those conducting or using health DCEs should carefully select, justify, and report the measurement and potential impact of participant understanding in their specific choice context. There remains scope for research into the different components of participant understanding, particularly related to engagement, the impact of participant understanding on DCE validity and reliability, the best measures of understanding, and methods to maximise participant understanding.

Electronic supplementary material

The online version of this article (10.1007/s40271-020-00467-y) contains supplementary material, which is available to authorized users.

Parent, provider and vaccinee preferences for HPV vaccination: A systematic review of discrete choice experiments

OBJECTIVES

To systematically review, appraise and evaluate available evidence regarding discrete-choice experiments (DCEs) for the human papilloma virus (HPV) vaccination in order to support policymakers in making reasonable and effective vaccination program implementation decisions.

METHODS

A systematic literature review was conducted using the databases PubMed and Embase for DCEs in HPV up to May 2019. Extracted data was tabulated and two checklists were used for the quality appraisal of the included studies. All attributes were categorized in outcome, process or costs attributes and the relative importance of attributes was calculated using the range method.

RESULTS

Out of 164 identified studies, 12 met the inclusion criteria. Eight were from high income countries (HICs) and four from low and middle-income countries (LMICs). Five studies each examined vaccinee and parent preferences, while only two assessed the providers' preferences. The studies were rather heterogenous in terms of the populations investigated, the attributes included and the methodologic approach. Overall, outcome measures were the most prominent attributes and effectiveness consistently yielded high relative importance scores. But also process factors, such as the age at vaccination, played an important role for decision making. Discrepancies between HICs and LMICs were most prominent for cost attributes.

CONCLUSION

The heterogenous preferences this review elicited highlight the importance of context when making decisions grounded on consumer preferences. Especially the lack of evidence from LMICs, where the burden of cervical cancer is highest, is worrisome. In order to increase uptake, close vaccination gaps and reduce current inequities in (reproductive) healthcare, policy makers need to understand the features that drive individual vaccination decisions and adapt national and clinical guidelines accordingly. Future research therefore needs to focus on LMICs in order to elicit preferences of those most vulnerable populations.

Using discrete choice experiments to develop and deliver patient-centered psychological interventions: a systematic review

Developing and/or tailoring psychological interventions to align with patient preferences is a critical component of patient-centered care and has the potential to improve patient engagement and treatment outcomes. Discrete choice experiments (DCEs) are a quantitative method of assessing patient preferences that offer numerous strengths (i.e., ability to account for trade-offs), but are not routinely incorporated into health psychology coursework, likely leaving many unaware of the potential benefits of this methodology. To highlight the potential applications of DCEs within health psychology, this systematic review synthesises previous efforts to utilise DCEs to inform the design of patient-centered psychological care, defined as interventions targeting psychological (e.g., depression, anxiety) or behavioural health (e.g., pain management, adherence) concerns. Literature searches were conducted in March 2017 and November 2019 for articles reporting on DCEs using the terms 'discrete choice', 'conjoint', or 'stated preference'. Thirty-nine articles met all inclusion criteria and used DCEs to understand patient preferences regarding psychosocial clinical services (n = 12), lifestyle behaviour change interventions (n = 11), HIV prevention and/or intervention services (n = 10), disease self-management programmes (n = 4), or other interventions (n = 2). Clinical implications as well as limitations and directions for future research are discussed.

Development of a Discrete-Choice Experiment (DCE) to Elicit Adolescent and Parent Preferences for Hypodontia Treatment

Objective

Our objective was to develop and test a discrete-choice experiment (DCE) survey to elicit adolescent and parent preferences for dental care for hypodontia (a developmental condition where one or more teeth fail to develop).

Methods

This was a mixed-methods study. Participants were adolescents (aged 12–16 years) with hypodontia and their parents and the dentists providing hypodontia care. Stage one entailed attribute development, as follows. (1) Attribute identification: systematic review of hypodontia literature; interviews with adolescents with hypodontia (n = 8) and parents (n = 8); observation of hypodontia clinical consultations (n = 5); environmental scan of hypodontia patient information resources (n = 30); and systematic analysis of social media posts (n = 176). (2) Attribute selection: stakeholder consultation to develop items for a questionnaire; rating and ranking questionnaire for adolescents with hypodontia and parents (n = 18); further stakeholder consultation. Stage two involved the development of the DCE survey, and stage three included the pre-testing using cognitive interviews with adolescents (n = 12) and parents (n = 8) to assess face and content validity.

Results

The attribute long list included 27 attributes focusing on service delivery and treatment outcome, from which seven ‘important’ attributes were selected for pre-testing. Cognitive interviewing suggested adolescents found the DCE choice tasks challenging to understand; the survey was modified to enhance its acceptability. One attribute was excluded as it showed poor validity with adolescents. Pre-testing suggested DCE choice tasks encouraged thinking and discussion about preferences for treatment.

Conclusions

Including the target respondent group in all stages of DCE development ensured the final DCE survey was valid and acceptable. DCE methods appear to be a useful tool for exploring joint decision making alongside conventional preference elicitation.

Electronic supplementary material

The online version of this article (10.1007/s40271-018-0338-0) contains supplementary material, which is available to authorized users.

Attributes influencing parental decision-making to receive the Tdap vaccine to reduce the risk of pertussis transmission to their newborn - outcome of a cross-sectional conjoint experiment in Spain and Italy

Pertussis vaccination of parents and household contacts (‘cocooning’) to protect newborn infants is an established strategy in many countries, although uptake may be low. Many aspects may influence such decision-making. We conducted a cross-sectional survey (NCT01890447) of households and other close contacts of newborns aged ≤6 months (or of expectant mothers in their last trimester) in Spain and Italy, using an adaptive discrete-choice experiment questionnaire. Aims were to assess the relative importance of attributes influencing vaccine adoption, and to estimate variation in vaccine adoption rates and the impact of cost on vaccination rates. Six hundred and fifteen participants (Spain, n = 313; Italy, n = 302) completed the survey. Of 144 available questionnaire scenarios, the most frequently selected (14% of respondents in both countries) were infant protection by household vaccination at vaccination center, recommendation by family physician and health authorities, with information available on leaflets and websites. The attribute with highest median relative importance was ‘reduction in source of infection’ in Spain (23.1%) and ‘vaccination location’ in Italy (18.8%). Differences between other attributes were low in both countries, with media attributes showing low importance. Over 80% of respondents indicated a definite or probable response to vaccine adoption (at no-cost) with estimated probability of adoption of 89–98%; applying vaccine costs (25€ per person) would reduce the probability of uptake by 7–20% in definite/probable respondents. Awareness of these determinants is helpful in informing Health Authorities and healthcare practitioners implementing a cocooning strategy for those populations where maternal immunization is not a preferred option.

HPV vaccination and sexual health in France: Empowering girls to decide

OBJECTIVE

Vaccination coverage against HPV in France is among the lowest in the industrialized world, although the public authorities have recently become aware of this issue. Few studies have looked at teenaged girls' representations of this vaccination, even though they are the most concerned by it. This qualitative study explored the experiences and representations of HPV vaccination by adolescent girls seeing doctors at least occasionally.

STUDY DESIGN

We used a written essay question to explore this issue among 101 adolescent girls at six urban medical centers and a semi-structured interview to discuss it in further depth with five of them. The analysis was lexicometric (ALCESTE®) and phenomenological (Interpretative Phenomenological Analysis).

RESULTS

These results are organized around four superordinate themes: the teenage girls' factual knowledge about this vaccine, their motives for and obstacles to vaccination, their involvement in this decision, and finally the need for information about and solutions to this issue.

CONCLUSIONS

Teenage girls know little about this vaccine and are more sensitive to the emotional discourse that surrounds it than to rational knowledge about it. The requirement for parental authorization for this vaccine reinforces the girls' lack of investment. Vaccination programs should integrate the HPV vaccine more thoroughly into general prevention concerning sexual health and should send a strong signal by offering minors anonymous vaccination free of charge, as is already the case in France for requests for contraception, the morning-after pill, elective abortion, and screening and treatment of sexually transmitted infections.

Quantifying the public's view on social value judgments in vaccine decision-making: A discrete choice experiment

Vaccination programs generate direct protection, herd protection and, occasionally, side effects, distributed over different age groups. This study elicits the general public's view on how to balance these outcomes in funding decisions for vaccines. We performed an optimal design discrete choice experiment with partial profiles in a representative sample (N = 1499) of the population in the United Kingdom in November 2016. Using a panel mixed logit model, we quantified, for four different types of infectious disease, the importance of a person's age during disease, how disease was prevented-via direct vaccine protection or herd protection-and whether the vaccine induced side effects. Our study shows clear patterns in how the public values vaccination programs. These diverge from the assumptions made in public health and cost-effectiveness models that inform decision-making. We found that side effects and infections in newborns and children were of primary importance to the perceived value of a vaccination program. Averting side effects was, in any age group, weighted three times as important as preventing an identical natural infection in a child whereas the latter was weighted six times as important as preventing the same infection in elderly aged 65-75 years. These findings were independent of the length or severity of the disease, and were robust across respondents' backgrounds. We summarize these patterns in a set of preference weights that can be incorporated into future models. Although the normative significance of these weights remains a matter open for debate, our study can, hopefully, contribute to the evaluation of vaccination programs beyond cost-effectiveness.

Individual Preferences for Child and Adolescent Vaccine Attributes: A Systematic Review of the Stated Preference Literature

BACKGROUND

Discrete choice experiments are increasingly used to assess preferences for vaccines and vaccine service delivery.

OBJECTIVES

To synthesize and critically assess the application of discrete choice experiments in childhood/adolescent vaccines, to describe how discrete choice experiments have been applied to understand preferences, and to evaluate the use of discrete choice experiment data to inform estimates of vaccine uptake.

METHODS

We conducted a systematic review of six electronic databases. Included studies were discrete choice experiments and conjoint analyses published from 2000 to 2016 related to childhood/adolescent vaccines where respondents were parents, children/adolescents, or service providers. Validity assessment was used to assess study quality and risk of bias.

RESULTS

In total, 27 articles were included, representing 21 different studies. A majority of articles were published between 2011 and 2016. Vaccines studied included human papillomavirus (24%), influenza (19%), meningococcal vaccines (14%), childhood vaccines (14%), hypothetical vaccines (10%), hepatitis B (5%), and diphtheria, tetanus, pertussis, hepatitis B, poliomyelitis, and Haemophilus influenzae type b (5%). Most studies assessed parent preferences (67%). The most common attributes were risk (24%), degree/duration of protection (21%), and cost (15%). Commonly reported outcome measures were estimates of uptake (33%), willingness-to-pay (22%), and other marginal rates of substitution (14%). Validity assessments yielded high scores overall. Areas of weakness included low response rates, inefficient experimental design, and failure to conduct formative qualitative work and a pilot of the discrete choice experiment.

CONCLUSION

This is the first systematic review of childhood/adolescent vaccine-related discrete choice experiments. In future, special attention should be paid to ensuring that choice context and discrete choice experiment design are compatible to generate reliable estimates of uptake.

Using Latent Class Analysis to Model Preference Heterogeneity in Health: A Systematic Review

BACKGROUND

Latent class analysis (LCA) has been increasingly used to explore preference heterogeneity, but the literature has not been systematically explored and hence best practices are not understood.

OBJECTIVE

We sought to document all applications of LCA in the stated-preference literature in health and to inform future studies by identifying current norms in published applications.

METHODS

We conducted a systematic review of the MEDLINE, EMBASE, EconLit, Web of Science, and PsycINFO databases. We included stated-preference studies that used LCA to explore preference heterogeneity in healthcare or public health. Two co-authors independently evaluated titles, abstracts, and full-text articles. Abstracted key outcomes included segmentation methods, preference elicitation methods, number of attributes and levels, sample size, model selection criteria, number of classes reported, and hypotheses tests. Study data quality and validity were assessed with the Purpose, Respondents, Explanation, Findings, and Significance (PREFS) quality checklist.

RESULTS

We identified 2560 titles, 99 of which met the inclusion criteria for the review. Two-thirds of the studies focused on the preferences of patients and the general population. In total, 80% of the studies used discrete choice experiments. Studies used between three and 20 attributes, most commonly four to six. Sample size in LCAs ranged from 47 to 2068, with one-third between 100 and 300. Over 90% of the studies used latent class logit models for segmentation. Bayesian information criterion (BIC), Akaike information criterion (AIC), and log-likelihood (LL) were commonly used for model selection, and class size and interpretability were also considered in some studies. About 80% of studies reported two to three classes. The number of classes reported was not correlated with any study characteristics or study population characteristics (p > 0.05). Only 30% of the studies reported using statistical tests to detect significant variations in preferences between classes. Less than half of the studies reported that individual characteristics were included in the segmentation models, and 30% reported that post-estimation analyses were conducted to examine class characteristics. While a higher percentage of studies discussed clinical implications of the segmentation results, an increasing number of studies proposed policy recommendations based on segmentation results since 2010.

CONCLUSIONS

LCA is increasingly used to study preference heterogeneity in health and support decision-making. However, there is little consensus on best practices as its application in health is relatively new. With an increasing demand to study preference heterogeneity, guidance is needed to improve the quality of applications of segmentation methods in health to support policy development and clinical practice.

Adolescent values for immunisation programs in Australia: A discrete choice experiment

Objectives

The importance of adolescent engagement in health decisions and public health programs such as immunisation is becoming increasingly recognised. Understanding adolescent preferences and further identifying barriers and facilitators for immunisation acceptance is critical to the success of adolescent immunisation programs. This study applied a discrete choice experiment (DCE) to assess vaccination preferences in adolescents.

Methods

This study was conducted as a cross-sectional, national online survey in Australian adolescents. The DCE survey evaluated adolescent vaccination preferences. Six attributes were assessed including disease severity, target for protection, price, location of vaccination provision, potential side effects and vaccine delivery method. A mixed logit model was used to analyse DCE data.

Results

This survey was conducted between December 2014 and January 2015. Of 800 adolescents aged 15 to 19 years, stronger preferences were observed overall for: vaccination in the case of a life threatening illness (p<0.001), lower price vaccinations (p<0.001), mild but common side effects (p = 0.004), delivery via a skin patch (p<0.001) and being administered by a family practitioner (p<0.001). Participants suggested that they and their families would be willing to pay AU$394.28 (95%CI: AU$348.40 to AU$446.92) more for a vaccine targeting a life threatening illness than a mild-moderate illness, AU$37.94 (95%CI: AU$19.22 to AU$57.39) more for being vaccinated at a family practitioner clinic than a council immunisation clinic, AU$23.01 (95%CI: AU$7.12 to AU$39.24) more for common but mild and resolving side effects compared to rare but serious side effects, and AU$51.80 (95%CI: AU$30.42 to AU$73.70) more for delivery via a skin patch than injection.

Conclusions

Consideration of adolescent preferences may result in improved acceptance of, engagement in and uptake of immunisation programs targeted for this age group.

Vaccine preferences and acceptance of older adults

BACKGROUND

Expanding vaccination programs for the older population might be important as older adults are becoming a larger proportion of the general population. The aim of this study is to determine the relative importance of vaccine and disease specific characteristics and acceptance for Dutch older adults, including pneumococcal disease, herpes zoster, pertussis vaccination, and influenza vaccination.

METHODS

A discrete choice experiment was conducted to generate choice data that was analyzed using a mixed multinomial logit statistical model.

RESULTS

Important factors that were associated with vaccination acceptance in older adults are high mortality risk of the infectious disease, high susceptibility of getting the infectious disease, and high vaccine effectiveness. Age, influenza vaccination in 2013 and self-perceived health score were identified as personal factors that affect vaccine preference. Potential vaccination rates of older adults were estimated at 68.1% for pneumococcal vaccination, 58.1% for herpes zoster vaccination, 53.9% for pertussis vaccination and 54.3% for influenza vaccination. For persons aged 50-65, potential vaccination rates were estimated at 58.1% for pneumococcal vaccination, 49.5% for herpes zoster vaccination, 43.9% for pertussis vaccination and 42.2% for influenza vaccination. For persons aged 65 and older, these were respectively 76.2%, 67.5%, 57.5% and 65.5%.

DISCUSSION

Our results suggest that older adults are most likely to accept pneumococcal vaccination of the four vaccines. Information provision accompanied with the implementation of a new vaccine has to be tailored for the individual and the vaccine it concerns. Special attention is needed to ensure high uptake among persons aged 50-65years.