Drivers of vaccine decision-making in South Africa: A discrete choice experiment

Perception of COVID-19 Vaccination and Uptake Willingness in Northern Nigeria: Understanding Strategies to Optimize Coverage

Background: Vaccination is a proven and safe method for combating COVID-19; however, coverage remains low in many low- and middle-income countries, including Nigeria. There is also a lack of contextual evidence regarding the public perception of and willingness to receive vaccines. This study aims to contribute to efforts to optimize the vaccination coverage and improve public health in northern Nigeria. Objective: This study investigated the perceptions of COVID-19 vaccination and willingness to uptake the vaccine in northern Nigeria, aiming to identify strategies for optimizing coverage and enhancing vaccination rates. Methods: A cross-sectional household survey was conducted across the Federal Capital Territory and five northern states in Nigeria. The survey assessed the respondents' perceptions of COVID-19, their knowledge of the COVID-19 vaccine, and their willingness to be vaccinated. Descriptive and inferential (multivariate logistic regression) statistical analyses were employed to characterize the population and identify predictors of vaccine uptake. Results: The mean age of the respondents was 28.00 years. The majority reported at least one piece of misinformation regarding COVID-19. While awareness of the vaccine was high, its actual uptake was low, and future willingness to receive the vaccine was also limited. Employment status emerged as a significant predictor of vaccine uptake, as determined through the multivariate analysis. Furthermore, collaboration with NGOs and community-based organizations (CBOs) was identified as the most effective strategy for enhancing vaccine uptake. Conclusions: This study found a concerningly low willingness to receive the COVID-19 vaccine among participants in northern Nigeria. To address this issue, we recommend establishing partnerships with NGOs and CBOs, implementing extensive public awareness campaigns, and conducting community outreach programs. These efforts should focus on dispelling misinformation, building community trust, and promoting vaccine uptake through culturally appropriate communication materials.

Lessons from a school-based vaccination response following a Diphtheria outbreak in eThekwini district, SA

Diphtheria is a life-threatening respiratory tract infection that causes outbreaks in susceptible populations. Between April and May 2018, an outbreak of diphtheria occurred in the eThekwini district. A school-based outbreak vaccination response was initiated to target vulnerable children and adolescents.

Contribution

This study adds to the limited data describing a school-based vaccination in an outbreak response and highlights successes and challenges. School-based outbreak vaccination response can rapidly increase vaccine coverage; however, additional community engagement may be required in vaccine-hesitant populations.

Preferences of pregnant women toward a future maternal Group B Streptococcus vaccine in China: A cross-sectional survey with a discrete choice experiment

Group B streptococcus (GBS) is a major cause of neonatal death worldwide. A GBS vaccine for pregnant women is under development and is expected to be available in the near future. The perceptions and preferences of pregnant women in China of GBS vaccines has not been investigated, and this study aimed to investigate pregnant women's awareness of GBS and their potential preferences for the GBS vaccine. A discrete choice experiment was conducted among pregnant women in hospitals from Shaanxi, Hunan, and Zhejiang provinces located in Western, Central, and Eastern China, respectively. A conditional logit model was used to analyze the data and calculate willingness to pay values and choice probabilities of different GBS vaccine programs. A total of 354 pregnant women were included in the final analysis, 45.8% of whom were willing to receive a GBS vaccine if it were licensed. Vaccine safety was the most important attribute of a future vaccine, while cost was the least important attribute. Compared with no vaccination, pregnant women had a strong preference for future GBS vaccination (ASC = 1.267, p < .001). Pregnant women's decisions were highly influenced by those of other pregnant women. Improving the safety, efficacy, and vaccination rate of the GBS vaccine in China is of great significance for future GBS vaccine development and vaccination. Compared to other variable options, the cost of a GBS vaccine was of the least importance among pregnant women in mainland China. These findings can inform public health policy decisions related to GBS vaccination in China.

Comparison of a full and partial choice set design in a labeled discrete choice experiment

Labeled discrete choice experiments (DCEs) commonly present all alternatives using a full choice set design (FCSD), which could impose a high cognitive burden on respondents. In the setting of employment preferences, this study explored if a partial choice set design (PCSD) reduced cognitive burden whilst maintaining convergent validity compared with a FCSD. Respondents' preferences between the two designs were investigated. In the experimental design, labeled utility functions were rewritten into a single generic utility function using label dummy variables to generate an efficient PCSD with 3 alternatives shown in each choice task (out of 6). The DCE was embedded in a nationwide survey of 790 Australian pharmacy degree holders where respondents were presented with both a block of FCSD and PCSD tasks in random order. The PCSD's impact on error variances was investigated using a heteroscedastic conditional logit model. The convergent validity of PCSD was based on the equality of willingness-to-forgo-expected-salary estimates from Willingness-to-pay-space mixed logit models. A nested logit model was used combined with respondents' qualitative responses to understand respondents' design preferences. We show a promising future use of PCSD by providing evidence that PCSD can reduce cognitive burden while satisfying convergent validity compared to FCSD.

What motivates adults to accept influenza vaccine? An assessment of incentives, ease of access, messaging, and sources of information using a discrete choice experiment

Seasonal influenza vaccination rates remain low, and contribute to preventable influenza cases, hospitalizations, and deaths in the US. While numerous interventions have been implemented to increase vaccine uptake, there is a need to determine which interventions contribute most to vaccine willingness, particularly among age groups with vaccination rates that have plateaued at suboptimal levels. This study aimed to quantify the relative effect of multiple interventions on vaccine willingness to receive influenza vaccine in three age groups using a series of hypothetical situations with different behavioral interventions. We assessed the relative impact of four categories of interventions: source of vaccine messages, type of vaccination messages, vaccination incentives, and ease of vaccine access using a discrete choice experiment. Within each category, we investigated the role of four different attributes to measure their relative contribution to willingness to be vaccinated by removing one option from each of the intervention categories. Among the 1,763 Minnesota residents who volunteered for our study, participants expressed vaccine willingness in over 80% of the scenarios presented. Easy access to drop-in vaccination sites had the greatest impact on vaccine willingness in all age groups. Among the younger age group, small financial incentives also contributed to high vaccine willingness. Our results suggest that public health programs and vaccination campaigns may improve their chances of successfully increasing vaccine willingness if they offer interventions preferred by adults, including facilitating convenient access to vaccination and offering small monetary incentives, particularly for young adults.

Parental preference for Haemophilus influenzae type b vaccination in Zhejiang Province, China: A discrete choice experiment

Background

China is the only country in the world that has not included the Haemophilus influenzae type b (Hib) vaccine in its National Immunization Program, making it more difficult to eliminate Hib-related diseases through Hib vaccination. It is necessary to study parental preferences for Hib vaccination to optimize vaccine promotion strategies in China.

Objective

This study aimed to investigate Chinese parental preference for five attributes of Hib vaccination, i.e., the place of origin, effectiveness, adverse event, doctors' recommendation, and the price of full vaccination when making a decision to vaccinate their children under 2 years old.

Methods

A cross-sectional survey was conducted in two cities in Zhejiang Province from November to December in 2020 using a discrete choice experiment (DCE). A mixed logit model was used to estimate participating parents' preference for Hib vaccination attributes included in the DCE. Subgroup analysis and probability analysis were also conducted to capture the heterogeneity and trade-off of parental preference for Hib vaccination.

Results

Data from 6,168 observations were included in the analyses. Parents of children are, on average, more likely to voice a positive preference for Hib vaccination. Such attributes of Hib vaccination as effectiveness and doctor's recommendation have a significant positive influence on parents' preference for Hib vaccination, while imported vaccines, adverse events, and the price of full vaccination have a significant negative influence on parents' preference. Parents with different demographic characteristics also existed heterogeneities in preference for Hib vaccination. Parents will make a trade-off on price if the Hib vaccine has a good performance on effectiveness and safety.

Conclusion

The study found that, regardless of the place of origin of the Hib vaccine, parents with children under 2 years old prefer to compromise on price if the vaccine has a better effectiveness and safety profile. A proactive recommendation from doctors would strengthen their willingness for Hib vaccination. These findings help aid the development of communication strategies with parents for Hib vaccination in China.

Effect of ontological insecurity on vaccination behavior against COVID-19: a hospital-based cross-sectional study

OBJECTIVE

Coronavirus disease 2019 (COVID-19) has brought great uncertainty to our society and it may have disrupted people's ontological security. Consequently, this hospital-based study concerns the impact of ontological insecurity on vaccination behavior against COVID-19.

STUDY DESIGN

This cross-sectional study was conducted among hospital inpatients.

METHODS

A questionnaire survey addressing inpatient ontological insecurity and vaccination behavior against COVID-19 was administered in Taizhou, China. A total of 1223 questionnaires were collected; specifically, 1185 of them were credible, for a validity rate of 96.9%.

RESULTS

The score of ontological insecurity was 13.27 ± 7.84, which was higher in participants who did not recommend vaccination for others than those who did (12.95 ± 8.25 vs 14.00 ± 6.78, P = 0.022). There was no difference between the vaccinated and unvaccinated groups (13.22 ± 7.96 vs 13.35 ± 7.67, P = 0.779). Lower ontological insecurity (odds ratio [OR] = 1.40, 95% confidence interval [CI]: 1.08-1.81) and being inoculated with COVID-19 vaccines (OR = 2.17, 95% CI: 1.67-2.82) were significantly associated with recommendation of COVID-19 vaccines to others after adjusting for sex, age, education, and occupation. Associations between low ontological insecurity and recommendations for COVID-19 vaccines were observed in men, adults aged 18-59 years, non-farmers, and vaccine recipients.

CONCLUSIONS

This study suggests that the ontological insecurity of participants affects their behavior of recommending the COVID-19 vaccination to others rather than getting vaccinated themselves. This promotion of vaccination can be considered from the perspective of improving ontological security in China.

An (un)healthy social dilemma: a normative messaging field experiment with flu vaccinations

BACKGROUND

Influenza seasons can be unpredictable and have the potential to rapidly affect populations, especially in crowded areas. Prior research suggests that normative messaging can be used to increase voluntary provision of public goods, such as the influenza vaccine. We extend the literature by examining the influence of normative messaging on the decision to get vaccinated against influenza.

METHODS

We conduct a field experiment in conjunction with University Health Services, targeting undergraduate students living on campus. We use four posters, randomized by living area clusters to advertise flu vaccination clinics during the Fall. The wording on the posters is varied to emphasize the individual benefits of the vaccine, the social benefits of the vaccine or both benefits together. We collect survey data for those vaccinated at the vaccination clinics, and for those not vaccinated via an online survey.

RESULTS

We find that any normative message increases the percentage of students getting the flu vaccine compared with no message. In terms of the likelihood of getting the flu vaccine, emphasizing both the individual and social benefits of vaccination has the largest increase in the vaccination rate (19-20 percentage point increase). However, flu vaccinations did not reach the herd immunity threshold (70% of students vaccinated).

CONCLUSIONS

This study provides evidence that there is a pro-social component that is relevant in individual vaccination decisions which should be accounted for when designing vaccination campaigns. The results of this normative, pro-social messaging experiment could be extended to other at-risk communities where the number of background risks is much larger. This is especially relevant nowadays, as other seasonal vaccines are being rolled out and younger adults are the ones with the lowest uptake.

COVID-19 vaccine hesitancy: a social media analysis using deep learning

Hesitant attitudes have been a significant issue since the development of the first vaccines-the WHO sees them as one of the most critical global health threats. The increasing use of social media to spread questionable information about vaccination strongly impacts the population's decision to get vaccinated. Developing text classification methods that can identify hesitant messages on social media could be useful for health campaigns in their efforts to address negative influences from social media platforms and provide reliable information to support their strategies against hesitant-vaccination sentiments. This study aims to evaluate the performance of different machine learning models and deep learning methods in identifying vaccine-hesitant tweets that are being published during the COVID-19 pandemic. Our concluding remarks are that Long Short-Term Memory and Recurrent Neural Network models have outperformed traditional machine learning models on detecting vaccine-hesitant messages in social media, with an accuracy rate of 86% against 83%.

What drives willingness to receive a new vaccine that prevents an emerging infectious disease? A discrete choice experiment among university students in Uganda

Background

There is a critical need to identify the drivers of willingness to receive new vaccines against emerging and epidemic diseases. A discrete choice experiment is the ideal approach to evaluating how individuals weigh multiple attributes simultaneously. We assessed the degree to which six attributes were associated with willingness to be vaccinated among university students in Uganda.

Methods

We conducted a single-profile discrete choice experiment at Makerere University in 2019. Participants were asked whether or not they would be vaccinated in 8 unique scenarios where attributes varied by disease risk, disease severity, advice for or against vaccination from trusted individuals, recommendations from influential figures, whether the vaccine induced indirect protection, and side effects. We calculated predicted probabilities of vaccination willingness using mixed logistic regression models, comparing health professional students with all other disciplines.

Findings

Of the 1576 participants, 783 (49.8%) were health professional students and 685 (43.5%) were female. Vaccination willingness was high (78%), and higher among health students than other students. We observed the highest vaccination willingness for the most severe disease outcomes and the greatest exposure risks, along with the Minister of Health’s recommendation or a vaccine that extended secondary protection to others. Mild side effects and recommendations against vaccination diminished vaccination willingness.

Interpretation

Our results can be used to develop evidence-based messaging to encourage uptake for new vaccines. Future vaccination campaigns, such as for COVID-19 vaccines in development, should consider acknowledging individual risk of exposure and disease severity and incorporate recommendations from key health leaders.

Immediate and informative feedback during a pandemic: Using stated preference analysis to predict vaccine uptake rates

In response to an emerging pandemic, there is urgent need for information regarding individual evaluation of risk and preferences toward mitigation strategies such as vaccinations. However, with social distancing policies and financial stress during an outbreak, traditional robust survey methodologies of face-to-face, probabilistic sampling, may not be feasible to deploy quickly, especially in developing countries. We recommend a protocol that calls for a sensitive survey design, acceptance of a web-based approach and adjustments for uncertainty of respondents, to deliver urgently needed information to policymakers as the public health crisis unfolds, rather than in its aftermath. This information is critical to tailor comprehensive vaccination campaigns that reach critical immunity thresholds. We apply our recommendations in a regional study of 16 Latin American countries in the month following index cases of COVID-19. We use a split-sample, contingent valuation approach to evaluate the effects of cost, duration of immunity and effectiveness of the vaccine. Our results show that cost and duration of immunity are significant factors in the decision to vaccinate, while the degree of effectiveness is insignificant, unless the vaccine is 100% effective. Income as well as perceived risk and severity of the virus are important determinants also.

Multi-perspectives systematic review on the applications of sentiment analysis for vaccine hesitancy

A substantial impediment to widespread Coronavirus disease (COVID-19) vaccination is vaccine hesitancy. Many researchers across scientific disciplines have presented countless studies in favor of COVID-19 vaccination, but misinformation on social media could hinder vaccination efforts and increase vaccine hesitancy. Nevertheless, studying people's perceptions on social media to understand their sentiment presents a powerful medium for researchers to identify the causes of vaccine hesitancy and therefore develop appropriate public health messages and interventions. To the best of the authors' knowledge, previous studies have presented vaccine hesitancy in specific cases or within one scientific discipline (i.e., social, medical, and technological). No previous study has presented findings via sentiment analysis for multiple scientific disciplines as follows: (1) social, (2) medical, public health, and (3) technology sciences. Therefore, this research aimed to review and analyze articles related to different vaccine hesitancy cases in the last 11 years and understand the application of sentiment analysis on the most important literature findings. Articles were systematically searched in Web of Science, Scopus, PubMed, IEEEXplore, ScienceDirect, and Ovid from January 1, 2010, to July 2021. A total of 30 articles were selected on the basis of inclusion and exclusion criteria. These articles were formed into a taxonomy of literature, along with challenges, motivations, and recommendations for social, medical, and public health and technology sciences. Significant patterns were identified, and opportunities were promoted towards the understanding of this phenomenon.

Will Americans Get Vaccinated? Predicting COVID-19 Vaccine Uptake Rates Under Contingent Scenarios

OBJECTIVES

Amid a pandemic, vaccines represent a promising solution for mitigating public health and economic crises, and an improved understanding of individuals' vaccination intentions is crucial to design optimal immunization campaigns. This study predicts uptake rates for different COVID-19 vaccine specifications and identifies personal characteristics that moderate an individual's responsiveness to vaccine attributes.

METHODS

We developed an online survey with contingent specifications of a COVID-19 vaccine, varying in effectiveness, risks of side effects, duration of immunity, and out-of-pocket cost. Using population-averaged logit models, we estimated vaccine uptake rates that account for uncertainty, heterogeneity across respondents, and interactions between vaccine and personal characteristics.

RESULTS

We obtained 3047 completed surveys. The highest uptake rate for an annual vaccine, 62%, is predicted when vaccine effectiveness is 80% to 90%, side effects are minimal, and the vaccine is provided at zero cost, with decreases seen in the uptake rate for less effective vaccines, for example, 50% for 50% to 60% effectiveness. Moreover, we found that Americans' response to vaccine effectiveness depends on their self-reported concern, that is, concerned respondents report a higher willingness to get vaccinated. Our findings also indicate that COVID-19 vaccine uptake rates decrease with vaccine cost and that responsiveness to vaccine cost is moderated by income.

CONCLUSIONS

Although providing the COVID-19 vaccine at zero cost will motivate many individuals to get vaccinated, a policy focused exclusively on vaccine cost may not be enough to reach herd immunity thresholds. Although those concerned with COVID-19 will participate, further evidence is needed on how to incentivize participation among the unconcerned (43%) to prevent further pandemic spread.

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.

Enablers and barriers to COVID-19 vaccine uptake: An international study of perceptions and intentions

The development of COVID-19 vaccines is occurring at unprecedented speeds, but require high coverage rates to be successful. This research examines individuals’ psychological beliefs that may act as enablers and barriers to vaccination intentions. Using the health beliefs model as a guide to our conceptual framework, we explore factors influencing vaccine hesitancy and health beliefs regarding risks and severity of the disease, along with individual variables such as income, age, religion, altruism, and collectivism. A questionnaire using newly created measures for various antecedents provided 4303 usable responses from Australia, Canada, England, New Zealand, and the United States. A factor analytic and structural equation model indicates that trust in vaccine approval, the perceived effectiveness of the vaccine for protecting others, and conspiracy beliefs are the most significant drivers of intentions to vaccinate. Older people, those seeking employment, and those who have received a recent influenza vaccine are more likely to be vaccinated against COVID-19. The findings have implications for improving communication strategies targeting individuals about the merits of vaccination, particularly focusing on younger individuals and expanded message framing to include altruistic considerations, and to improve government transparency regarding the effectiveness and side effects of vaccines.

Preferences for herpes zoster vaccination among adults aged 50 years and older in the United States: results from a discrete choice experiment

BACKGROUND

Most adults, and disproportionately fewer African-Americans, have not received herpes zoster (HZ) vaccination despite current recommendations. This study (GSK study identifiers: 208677/HO-17-18066) assessed HZ vaccination preferences among adults aged ≥ 50 years.

RESEARCH DESIGN AND METHODS

In this discrete choice experiment, respondents chose among a 'no vaccine' option and two HZ vaccine profiles, characterized by seven attributes, in a series of choice questions. Random-parameters logit results were used to predict likely vaccine uptake. Subgroup and latent class analysis of African-American's preferences were performed.

RESULTS

The preference weight for choosing HZ vaccines over no vaccine was statistically significant among the 1,454 respondents (71.9% whites; 25.2% African-Americans). Out-of-pocket (OOP) cost and vaccine effectiveness (VE) were the most important attributes. The African-American and the non-African-American subgroups had statistically significant differences in preferences (χ² = 59.91, p < 0.001), mainly driven by OOP cost and VE. Latent class analysis identified three groups of African-American respondents with systematically different preferences; two comprised likely-vaccinators, with one being more cost sensitive at lower price thresholds, and one likely non-vaccinators.

CONCLUSIONS

For all respondents, HZ vaccine choices were most sensitive to total OOP cost, followed by VE.

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.

Factors influencing Covid-19 vaccine acceptance across subgroups in the United States: Evidence from a conjoint experiment

Public health officials warn that the greatest barrier to widespread vaccination against Covid-19 will not be scientific or technical, but the considerable public hesitancy to take a novel vaccine. Understanding the factors that influence vaccine acceptance is critical to informing public health campaigns aiming to combat public fears and ensure broad uptake. Employing a conjoint experiment embedded on an online survey of almost 2,000 adult Americans, we show that the effects of seven vaccine attributes on subjects’ willingness to vaccinate vary significantly across subgroups. Vaccine efficacy was significantly more influential on vaccine acceptance among whites than among Blacks, while bringing a vaccine to market under a Food and Drug Administration Emergency Use Authorization had a stronger adverse effect on willingness to vaccinate among older Americans and women. Democrats were more sensitive to vaccine efficacy than Republicans, and both groups responded differently to various endorsements of the vaccine. We also explored whether past flu vaccination history, attitudes toward general vaccine safety, and personal contact with severe cases of Covid-19 can explain variation in group vaccination hesitancy. Many subgroups that exhibit the greatest Covid-19 vaccine hesitancy did not report significantly lower frequencies of flu vaccination. Several groups that exhibited greater Covid-19 vaccine hesitancy also reported greater concerns about vaccine safety generally, but others did not. Finally, subgroup variation in reported personal contact with severe cases of Covid-19 did not strongly match subgroup variation in vaccine acceptance.

Vaccine hesitancy in the global south: Towards a critical perspective on global health

The complex phenomenon of vaccine hesitancy has been causing increasing global concern. This systematic review aims at analysing the state of art of scientific literature concerning vaccine hesitancy in Latin America and Africa, observing if: (i) they use the same research trends as the global North; and (ii) the parameters recommended by the World Health Organization (WHO) and taken from the experience of the global North are adequate to the Global South's context. This review analyses empirical, qualitative, quantitative, or mixed-study publications, from 2015 to 2020, available at five different databases. The studies produced in the Global South bring up important context-specific issues, such as issues of access (that are not included in the WHO's definition of vaccine hesitancy), cultural and religious issues, reactions to governments, reactions to recent episodes of vaccine tests on populations, and reactions to past of colonial violence. Initiatives to understand the phenomenon based on methodological and conceptual frameworks from the global North alone can cause wrongful conclusions.

No Such Thing as a Free-Rider? Understanding Drivers of Childhood and Adult Vaccination through a Multicountry Discrete Choice Experiment

Increased vaccine hesitancy and refusal negatively affects vaccine uptake, leading to the reemergence of vaccine preventable diseases. We aim to quantify the relative importance of factors people consider when making vaccine decisions for themselves, or for their child, with specific attention for underlying motives arising from context, such as required effort (accessibility) and opportunism (free riding on herd immunity). We documented attitudes towards vaccination and performed a discrete choice experiment in 4802 respondents in The United Kingdom, France and Belgium, eliciting preferences for six attributes: (1) vaccine effectiveness, (2) vaccine preventable disease burden, (3) vaccine accessibility in terms of copayment, vaccinator and administrative requirements, (4) frequency of mild vaccine-related side-effects, (5) vaccination coverage in the country’s population and (6) local vaccination coverage in personal networks. We distinguished adults deciding on vaccination for themselves from parents deciding for their youngest child. While all attributes were found to be significant, vaccine effectiveness and accessibility stood out in all (sub)samples, followed by vaccine preventable disease burden. We confirmed that people attach more value to severity of disease compared to its frequency, and discovered that peer influence dominates free-rider motives, especially for the vaccination of children. These behavioral data are insightful for policy and are essential to parameterize dynamic vaccination behavior in simulation models. In contrast to what most game theoretical models assume, social norms dominate free-rider incentives. Policy-makers and healthcare workers should actively communicate on high vaccination coverage, and draw attention to the effectiveness of vaccines while optimizing their practical accessibility.

Impact of Recommended Maternal Vaccination Programs on the Clinical Presentation of SARS-CoV-2 Infection: A Prospective Observational Study

The COVID-19 pandemic has raised questions about the possible cross immunity resulting from common vaccination programs and SARS-CoV-2 infection. Therefore, the Spanish Obstetric Emergency group performed a multicenter prospective study on the vaccination status of Influenza and Tdap (diphtheria, tetanus and pertussis vaccine boost administered in adulthood) in consecutive cases of SARS-CoV-2 infection in a pregnancy cohort, in order to assess its possible association with the clinical presentation and severity of symptoms of SARS-CoV-2 infection, as well as to determine the factors that may affect vaccination adherence. A total of 1150 SARS-CoV-2 positive pregnant women from 78 Spanish hospitals were analyzed: 183 had not received either vaccine, 23 had been vaccinated for Influenza only, 529 for Tdap only and 415 received both vaccines. No association was observed between the vaccination status and the clinical presentation of SARS-CoV-2 infection and/or the severity of symptoms. However, a lower adherence to the administration of both vaccines was observed in the Latin-American subgroup. Based on the results above, we reinforce the importance of maternal vaccination programs in the actual pandemic. Health education campaigns should be specially targeted to groups less likely to participate in these programs, as well as for a future SARS-CoV-2 vaccination campaign.

Quantifying preferences around vaccination against frequent, mild disease with risk for vulnerable persons: A discrete choice experiment among French hospital health care workers

The individual determinants of vaccine acceptance among health workers (HCWs) have been described in the literature, but there is little evidence regarding the impact of vaccine characteristics and contextual factors (e.g., incentives, communication) on vaccination intentions. We developed a single profile discrete choice experiment (DCE) to assess the impact of seven attributes on stated vaccination intention against an unnamed disease, described as frequent with rapid clinical evolution and epidemic potential (similar to influenza or pertussis). Attributes evaluated vaccine characteristics (effectiveness, security profile), inter-individual aspects (epidemic risk, controversy, potential for indirect protection, vaccine coverage) and incentives (e.g., badge, hierarchical injunction). A total of 1214 French hospital-based HCWs, recruited through professional organizations, completed the online DCE questionnaire. The relative impact of each attribute was estimated using random effects logit models on the whole sample and among specific subgroups. Overall, 52% of included HCWs were vaccinated against influenza during 2017-18 and the average vaccination acceptance rate across all scenarios was 58%. Aside from the management stance, all attributes' levels had significant impact on vaccination decisions. Poor vaccine safety had the most detrimental impact on stated acceptance (OR 0.04 for the level controversy around vaccine safety). The most motivating factor was protection of family (OR 2.41) and contribution to disease control (OR 2.34). Other motivating factors included improved vaccine effectiveness (OR 2.22), high uptake among colleagues (OR 1.89) and epidemic risk declared by health authorities (OR 1.76). Social incentives (e.g., a badge I'm vaccinated) were dissuasive (OR 0.47). Compared to HCWs previously vaccinated against influenza, unvaccinated HCWs who were favorable to vaccination in general were most sensitive towards improved vaccine effectiveness. Our study suggests that vaccine safety considerations dominate vaccine decision-making among French HCWs, while adapted communication on indirect protection and social conformism can contribute to increase vaccination acceptance.

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.

Awareness of HPV and drivers of HPV vaccine uptake among university students: A quantitative, cross-sectional study

HPV vaccination is a milestone in primary prevention. However in Italy, vaccine coverage is still nowhere near the target of 95%. We investigated factors associated with inclination to get vaccinated in university students, as they are likely to have just assumed a central role in their healthcare decision-making. University students aged 18-25 were asked to fill in a questionnaire. The effect of socio-demographic and behavioural characteristics on HPV awareness was assessed with a logistic regression adjusting for age, gender, nationality, degree course, relationship, age at first intercourse, number of sexual partners, smoking, sexual orientation, past diagnosis of STDs and knowledge of people who had received HPV vaccine. A second regression adjusting also for information sources, awareness and knowledge investigated factors associated with inclination to receive vaccine. Nine thousand nine hundred and eighty-eight questionnaires were included (response rate 91.3%); awareness of HPV and vaccine was 83.3% and 69.9% respectively. Awareness (AOR: 3.3; 95% CI: 2.3-4.6) and a good knowledge positively affected acceptability, as well as a previous diagnosis of STDs and knowledge of vaccinated people. Healthcare workers (AOR: 1.6; 95% CI: 1.4-1.9) and family members (AOR: 1.7; 95% CI: 1.4-2.1) were the most influencing information sources, even if knowledge of vaccinated people was by far more persuasive (AOR: 2.7; 95% CI: 2.2-3.3). Only 12% of participants were acquainted with skin to skin HPV transmission, while 75% believed in a full effectiveness of condom; less than 22% associated HPV with cancer (other than cervical cancer). Efforts to increase awareness are likely to be worth considering that: awareness is the main determinant of vaccine acceptance; only 50% of individuals not interested in receiving vaccine were aware of it; males are much less aware (AOR: 0.09; 95% CI: 0.07-0.11). Moreover, this study spotlights some misconceptions around HPV and acknowledges a pivotal role of healthcare workers, family and peer influence.

Preferential differences in vaccination decision-making for oneself or one's child in The Netherlands: a discrete choice experiment

BACKGROUND

To optimize the focus of future public information campaigns in The Netherlands promoting the uptake of vaccines among adults and children, we quantified the contribution of several attributes to the vaccination decision.

METHOD

We performed a discrete choice experiment (DCE) among Dutch adults including six attributes, i.e. vaccine effectiveness, vaccine-preventable burden of disease (specified in severity and frequency), accessibility of vaccination in terms of co-payment and prescription requirements, frequency of mild side-effects, population-level vaccination coverage and local vaccination coverage among family and friends. Participants answered the DCE from their own perspective ('oneself' group) or with regard to a vaccine decision for their youngest child ('child' group). The data was analysed by means of panel mixed logit models.

RESULTS

We included 1547 adult participants (825 'oneself' and 722 'child'). Vaccine effectiveness was the most important attribute in the 'oneself' group, followed by burden of disease (relative importance (RI) 78%) and accessibility (RI 76%). In the 'child' group, burden of disease was most important, but tied closely with vaccine effectiveness (RI 97%). Of less importance was the risk of mild vaccine-related side-effects and both population and local vaccination coverage. Interestingly, participants were more willing to vaccinate when uptake among the population or family and friends was high, indicating that social influence and social norms plays a role.

CONCLUSIONS

Vaccine effectiveness and disease severity are key attributes in vaccination decision-making for adults making a decision for themselves and for parents who decide for their children. Hence, public information campaigns for both adult and child vaccination should primarily focus on these two attributes. In addition, reinforcing social norms may be considered.

Current tools available for investigating vaccine hesitancy: a scoping review protocol

INTRODUCTION

Vaccine hesitancy, defined as the delay in acceptance or refusal of vaccination despite availability of vaccination services is responsible in part for suboptimal levels of vaccination coverage worldwide. The WHO recommends that countries incorporate plans to measure and address vaccine hesitancy into their immunisation programmes. This requires that governments and health institutions be able to detect concerns about vaccination in the population and monitor changes in vaccination behaviours. To do this effectively, tools to detect and measure vaccine hesitancy are required. The purpose of this scoping review is to give a broad overview of currently available vaccine hesitancy measuring tools and present a summary of their nature, similarities and differences.

METHODS AND ANALYSIS

The review will be conducted using the framework for scoping review proffered by Arksey and O'Malley. It will comply with the Preferred Reporting Items for Systematic reviews and Meta-Analyses extension for Scoping Reviews' guidelines. The broader research question of this review is: what vaccine hesitancy measuring tools are currently available?Search strategies will be developed using controlled vocabulary and selected keywords. PubMed, Web of Science, Scopus and reference lists of relevant publications will be searched. Titles and abstracts will be independently screened by two authors and data from full-text articles meeting the inclusion criteria will be extracted independently by two authors using a pretested data charting form. Discrepancies will be resolved by discussion and consensus. Results will be presented using descriptive statistics such as percentages, tables, charts and flow diagrams as appropriate. Narrative analysis will be used to summarise the findings of the review.

ETHICS AND DISSEMINATION

Ethics approval is not required for the review. It will be submitted as part of a doctoral thesis, presented at conferences and published in a peer-reviewed journal.

TRIAL REGISTRATION NUMBER

https://osf.io/x8fjk/.