A 680,000-person megastudy of nudges to encourage vaccination in pharmacies

Enhancing COVID-19 booster vaccination among the elderly through text message reminders

The BOOST (Booster promotion for older outpatients using SMS text reminders) program at Taipei Veterans General Hospital assessed the effectiveness of text message reminders in enhancing COVID-19 booster vaccination rates among the elderly, guided by the Health Belief Model (HBM). Targeting patients aged 65 and above, eligible yet unvaccinated for a COVID-19 booster, this cohort study sent personalized reminders a week prior to their scheduled appointments between April 18, 2022, and May 12, 2022, acting as cues to action to enhance vaccination uptake by overcoming perceived barriers and raising awareness of benefits. Over 5 weeks, the study observed a 38% increase in vaccination rate among 3,500 eligible patients, markedly surpassing the concurrent national rate increase of 4% for the same demographic. The majority of vaccinations occurred within two weeks after the reminder, illustrating the effectiveness of the strategy. Cox regression analysis identified age and time since last vaccination as significant predictors of responsiveness, with those aged 65-74 and 75-84 showing higher uptake, particularly when reminders were sent within 4 months after the last dose. A single reminder proved to be effective. The findings of this study demonstrate the potential of SMS reminders to promote COVID-19 vaccination among the elderly through the strategic use of HBM principles, suggesting a feasible and effective approach to public health communication.

Predictors of Change in Vaccination Decisions Among the Vaccine Hesitant: Examining the Roles of Age and Intolerance of Uncertainty

BACKGROUND

Vaccine hesitancy and resistance pose significant threats to controlling pandemics and preventing infectious diseases. In a group of individuals unvaccinated against the disease caused by the SARS-CoV-2 coronavirus (COVID-19), we investigated how age, intolerance of uncertainty (IU), and their interaction affected the likelihood of having changed one's vaccination decision a year later. We hypothesized that higher IU would increase the likelihood of becoming vaccinated, particularly among individuals of younger age. We predicted that this effect would remain significant, even after controlling for delay discounting and trust in science.

PURPOSE

The goal of this research was to understand the factors influencing changes in vaccination decisions among the vaccine hesitant.

METHODS

In a larger longitudinal study, ~7,500 participants from Prolific.co completed demographic and vaccination status questions, a delay discounting task, and the Intolerance of Uncertainty Scale in June-August 2021. Approximately 3,200 participants completed a follow-up survey in July-August 2022, answering questions about vaccination status, reasons for vaccination decision, and trust in science. We analyzed data from 251 participants who initially had no intention of getting vaccinated and completed the follow-up survey; 38% reported becoming vaccinated in the intervening year.

RESULTS

Data were analyzed using multilevel logistic regression. Over and above other factors related to vaccination decisions (delay discounting, trust in science), younger participants were more likely to change their decision and become vaccinated a year later, especially if they had higher IU, confirming our predictions. Primary reasons for becoming vaccinated were necessity and seeking protection against the virus.

CONCLUSIONS

These findings highlight the complex interplay between age, uncertainty, and vaccination decisions, and inform health policies by suggesting the need for tailoring interventions to specific concerns in different age groups.

Effectiveness of WhatsApp based debunking reminders on follow-up visit attendance for individuals with hypertension: a randomized controlled trial in India

BACKGROUND

Individuals with high blood pressure in India often miss essential follow-up visits. Missed visits contribute to gaps across the hypertension care continuum and preventable cardiovascular disease. Widespread misconceptions around hypertension care and treatment may contribute to low follow-up attendance rates, but to date, there is limited evidence of the effect of interventions to debunk such misconceptions on health-seeking behavior. We conducted a randomized controlled trial to measure whether combining information debunking commonly-held misconceptions with a standard reminder reduces missed follow-up visits among individuals with high blood pressure and investigated whether any observed effect was moderated through belief change.

METHODS

We recruited 388 patients with uncontrolled blood pressure from the outpatient wards of two public sub-district hospitals in Punjab, India. Participants randomly assigned to the intervention arm received two WhatsApp messages, sent 3 and 1 days before their physician-requested follow-up visit. The WhatsApp message began with a standard reminder, reminding participants of their upcoming follow-up visit and its purpose. Following the standard reminder, we included brief debunking statements aimed at acknowledging and correcting common misconceptions and misbeliefs about hypertension care seeking and treatment. Participants in the control group received usual care and did not receive any messages.

RESULTS

We did not find evidence that the enhanced WhatsApp reminders improved follow-up visit attendance (Main effect: 2.2 percentage points, p-value = 0.603), which remained low across both treatment (21.8%, 95% CI: 15.7%, 27.9%) and control groups (19.6%, 95% CI: 14.2%, 25.0%). Participants had widespread misconceptions about hypertension care but our debunking messages did not successfully correct these beliefs (p-value = 0.187).

CONCLUSIONS

This study re-affirms the challenge of continuity of care for chronic diseases in India and suggests that simple phone-based health communication methods may not suffice for changing prevalent misconceptions and improving health-seeking behavior.

TRIAL REGISTRATION

The trial began on July 18th. We registered the trial on July 18th (before recruitment began), including the main outcomes, on the German Clinical Trial Register [Identifier: DRKS00029712] and published a pre-analysis plan in the Open Science Framework [osf.io/67g35].

Electronic nudges for sustained influenza vaccination uptake in older adults: the nationwide randomized NUDGE-FLU-2 trial

Digital letter interventions have proven effective in increasing influenza vaccination rates. In this trial, we sought to further refine these strategies and investigated whether the effectiveness of the strategies could be sustained across consecutive influenza seasons. We enrolled all eligible Danish citizens 65 years of age or older in a nationwide registry-based randomized implementation trial during the 2023-2024 influenza season. Households of participants were randomly assigned in a 2.45:1:1:1:1:1:1 ratio to usual care or six different behaviorally informed electronic letter-based nudges delivered before the influenza vaccination period. The primary endpoint was receipt of influenza vaccination. Statistical analyses accounted for household-level clustering. A total of 881,373 participants (mean age 74.1 ± 6.5 years, 52.1% female) were randomized across 649,487 households. The primary endpoint was met; influenza vaccination rates were higher in the pooled intervention letter group compared to usual care (76.32% versus 76.02%; difference, 0.31 percentage points; 99.29% confidence interval, 0.00-0.61; P = 0.007). Although no individual letter significantly increased influenza vaccination rates, the directionality of effect was consistent across all letters. Effectiveness was particularly pronounced in participants who had not received influenza vaccination during the preceding season (Pinteraction = 0.010). Effectiveness was consistent regardless of whether participants had received a similar electronic letter-based nudge in the preceding season (Pinteraction = 0.26). In summary, electronic letter-based nudges successfully increased influenza vaccination among older adults, and our results suggest that these highly scalable strategies can be implemented effectively and safely across consecutive vaccination seasons.ClinicalTrials.gov registration: NCT06030726 .

You can't nudge into vaccination: Comparing the effects of nudge types and Covid-19 vaccination attitudes on vaccine willingness

Nudges can be an effective strategy to promote vaccination. However, it is necessary to better identify the characteristics of nudges that produce the strongest effects and how they interact with individuals' attitudes. Here we sequentially test the effectiveness of three nudge characteristics (framing, nudge type, and presentation modality) and the role of participants' attitudes toward Covid-19 vaccination, social solidarity and authoritarianism in vaccination decisions. In studies 1-4, participants were presented with a nudge manipulating a target characteristic (e.g. positive/negative framing, nudge type) and measuring willingness to vaccinate and related variables compared a control nudge. Study 5 used a single combined nudge reflecting the combination of successful nudges in previous studies. Results over all studies show that nudging has unreliable effects while vaccine attitudes are more reliably linked to all measures of vaccines willingness. These results suggest that attitudes play a more reliable role on effective adoption of vaccinations.

Mortality risk information and health-seeking behavior during an epidemic

In a context where pessimistic survival perceptions have been widespread as a result of the HIV/AIDS epidemic (Fig. 1 A), we study vaccine uptake and other health behaviors during the recent COVID-19 pandemic. Leveraging a longitudinal cohort study in rural Malawi that has been followed for up to 25 y, we document that a 2017 mortality risk information intervention designed to reduce pessimistic mortality perceptions (Fig. 1 B) resulted in improved health behavior, including COVID-19 vaccine uptake (Fig. 1 C). We also report indirect effects for siblings and household members. This was likely the result of a reinforcing process where the intervention triggered engagement with the healthcare system and stronger beliefs in the efficacy of modern biomedical treatments, which led to the adoption of health risk reduction behavior, including vaccine uptake. Our findings suggest that health information interventions focused on survival perceptions can be useful in promoting health behavior and participation in the formal healthcare system, even during health crises-such as the COVID-19 pandemic-that are unanticipated at the time of the intervention. We also note the importance of the intervention design, where establishing rapport, tailoring the content to the local context, and spending time with respondents to convey the information contributed to the salience of the message.

Megastudy shows that reminders boost vaccination but adding free rides does not

Encouraging routine COVID-19 vaccinations is likely to be a crucial policy challenge for decades to come. To avert hundreds of thousands of unnecessary hospitalizations and deaths, adoption will need to be higher than it was in the autumn of 2022 or 2023, when less than one-fifth of Americans received booster vaccines1,2. One approach to encouraging vaccination is to eliminate the friction of transportation hurdles. Previous research has shown that friction can hinder follow-through3 and that individuals who live farther from COVID-19 vaccination sites are less likely to get vaccinated4. However, the value of providing free round-trip transportation to vaccination sites is unknown. Here we show that offering people free round-trip Lyft rides to pharmacies has no benefit over and above sending them behaviourally informed text messages reminding them to get vaccinated. We determined this by running a megastudy with millions of CVS Pharmacy patients in the United States testing the effects of (1) free round-trip Lyft rides to CVS Pharmacies for vaccination appointments and (2) seven different sets of behaviourally informed vaccine reminder messages. Our results suggest that offering previously vaccinated individuals free rides to vaccination sites is not a good investment in the United States, contrary to the high expectations of both expert and lay forecasters. Instead, people in the United States should be sent behaviourally informed COVID-19 vaccination reminders, which increased the 30-day COVID-19 booster uptake by 21% (1.05 percentage points) and spilled over to increase 30-day influenza vaccinations by 8% (0.34 percentage points) in our megastudy. More rigorous testing of interventions to promote vaccination is needed to ensure that evidence-based solutions are deployed widely and that ineffective but intuitively appealing tools are discontinued.

The Costs of Polarizing a Pandemic: Antecedents, Consequences, and Lessons

Polarization has been rising in the United States of America for the past few decades and now poses a significant-and growing-public-health risk. One of the signature features of the American response to the COVID-19 pandemic has been the degree to which perceptions of risk and willingness to follow public-health recommendations have been politically polarized. Although COVID-19 has proven more lethal than any war or public-health crisis in American history, the deadly consequences of the pandemic were exacerbated by polarization. We review research detailing how every phase of the COVID-19 pandemic has been polarized, including judgments of risk, spatial distancing, mask wearing, and vaccination. We describe the role of political ideology, partisan identity, leadership, misinformation, and mass communication in this public-health crisis. We then assess the overall impact of polarization on infections, illness, and mortality during the pandemic; offer a psychological analysis of key policy questions; and identify a set of future research questions for scholars and policy experts. Our analysis suggests that the catastrophic death toll in the United States was largely preventable and due, in large part, to the polarization of the pandemic. Finally, we discuss implications for public policy to help avoid the same deadly mistakes in future public-health crises.

Negativity in online news coverage of vaccination rates in Serbia: a content analysis

OBJECTIVE

This content analysis study explored how online news media communicates and frames vaccination rates and herd immunity (the effect where enough people are immune, the virus is contained).

METHODS

We analyzed 160 vaccination-related news stories by nine highest-trafficked news websites in Serbia, published July-December 2017, around the start of the measles outbreak. We coded both the news story as a whole and every vaccination-rate mention (N = 339).

RESULTS

News stories framed current vaccination rates and changes in them in a predominantly negative way (175/241 and 67/98 mentions, respectively) (e.g., "only 50% vaccinated", "fewer parents vaccinating their children"), especially when referring to the measles vaccine (202/262 mentions). A total of 23/86 of news stories mentioning vaccination rates did not provide any numerical values. Reference groups for vaccination rates were rarely specified. Out of the 32 news stories mentioning herd immunity, 11 explained the effect.

CONCLUSIONS

Even routine communication of vaccination rates can be biased through negative frames and imprecise descriptions. Lamenting low immunization rates could activate a negative descriptive social norm ("many people are not getting vaccinated"), which may be especially ill-advised in the absence of an explanation of the social benefit of achieving herd immunity through vaccination.

Increasing the use of telemedicine: A field experiment

Patients are reluctant to use telemedicine health services, compared to its substitute in-person visits. One reason is that telemedicine can be accurately evaluated and compared to its substitute only after the product has been adopted and experienced. As such, an intervention that increases the probability of a first experience can have lasting effects. This article reports the results of a randomized field experiment conducted in collaboration with a health insurance company. During the intervention, half of the households out of 3,469 in the sample received periodic e-mails with information about the available services. It effectively increased the take-up and demand for telemedicine. Within the first 8 months of the experiment, patients assigned to the treatment group were 6 percentage points more likely to have used the service at least once (and had about five times the odds of using telemedicine compared to those in the control group). Eight months after the start of the intervention, the number of virtual consultations by the treatment group was six times larger than that of the control group. These results, even if limited by the sample and context in which the intervention took place, provide additional evidence about how information interventions can increase technological take-up within the health sector and could serve as the stepping stone for evaluating the impact of telemedicine on health outcomes causally.

Rationale and design of NUDGE-FLU-CHRONIC and NUDGE-FLU-2: Two nationwide randomized trials of electronic nudges to increase influenza vaccination among patients with chronic diseases and older adults during the 2023/2024 influenza season

BACKGROUND

Yearly influenza vaccination is strongly recommended for older adults and patients with chronic diseases including cardiovascular disease (CVD); however, vaccination rates remain suboptimal, particularly among younger patients. Electronic letters incorporating behavioral nudges are highly scalable public health interventions which can potentially increase vaccination, but further research is needed to determine the most effective strategies and to assess effectiveness across different populations. The purpose of NUDGE-FLU-CHRONIC and NUDGE-FLU-2 are to evaluate the effectiveness of electronic nudges delivered via the Danish governmental electronic letter system in increasing influenza vaccination among patients with chronic diseases and older adults, respectively.

METHODS

Both trials are designed as pragmatic randomized implementation trials enrolling all Danish citizens in their respective target groups and conducted during the 2023/2024 influenza season. NUDGE-FLU-CHRONIC enrolls patients aged 18-64 years with chronic diseases. NUDGE-FLU-2 builds upon the NUDGE-FLU trial conducted in 2022/2023 and aims to expand the evidence by testing both previously successful and new nudges among adults ≥65 years during a subsequent influenza season. Persons with exemptions from the electronic letter system are excluded from both trials. In both trials, participants are randomized in a 2.45:1:1:1:1:1:1 ratio to either receive no electronic letter (usual care) or to receive one of 6 different behaviorally informed electronic letters. NUDGE-FLU-CHRONIC has randomized 299,881 participants with intervention letters delivered on September 24, 2023, while NUDGE-FLU-2 has randomized 881,373 participants and delivered intervention letters on September 13, 2023. Follow-up is currently ongoing. In both trials, the primary endpoint is receipt of influenza vaccination on or before January 1, 2024, and the secondary endpoint is time to vaccination. Clinical outcomes including respiratory and cardiovascular hospitalizations, all-cause hospitalization, and mortality are included as prespecified exploratory endpoints. Prespecified individual-level pooled analyses will be conducted across NUDGE-FLU, NUDGE-FLU-CHRONIC, and NUDGE-FLU-2.

DISCUSSION

NUDGE-FLU-CHRONIC is the first nationwide randomized trial of electronic nudges to increase influenza vaccination conducted among 18-64-year-old high-risk patients with chronic diseases. NUDGE-FLU-2 will provide further evidence on the effectiveness of electronic nudges among older adults ≥65 years. Collectively, the NUDGE-FLU trials will provide an extensive evidence base for future public health communications.

TRIAL REGISTRATION

NUDGE-FLU-CHRONIC: Clinicaltrials.gov: NCT06030739, registered September 11, 2023, https://clinicaltrials.gov/study/NCT06030739. NUDGE-FLU-2: Clinicaltrials.gov: NCT06030726, registered September 11, 2023, https://clinicaltrials.gov/study/NCT06030726.

Field testing the transferability of behavioural science knowledge on promoting vaccinations

As behavioural science is increasingly adopted by organizations, there is a growing need to assess the robustness and transferability of empirical findings. Here, we investigate the transferability of insights from various sources of behavioural science knowledge to field settings. Across three pre-registered randomized controlled trials (RCTs, N = 314,824) involving a critical policy domain-COVID-19 booster uptake-we field tested text-based interventions that either increased vaccinations in prior field work (RCT1, NCT05586204), elevated vaccination intentions in an online study (RCT2, NCT05586178) or were favoured by scientists and non-experts (RCT3, NCT05586165). Despite repeated exposure to COVID-19 vaccination messaging in our population, reminders and psychological ownership language increased booster uptake, replicating prior findings. However, strategies deemed effective by prediction or intention surveys, such as encouraging the bundling of COVID-19 boosters and flu shots or addressing misconceptions, yielded no detectable benefits over simple reminders. These findings underscore the importance of testing interventions' transferability to real-world settings.

The Nudging Effect of a Reminder Letter to Reduce Duplicated Medications: A Randomized Controlled Trial

BACKGROUND

The increasing trend of multiple chronic conditions across the world has worsened the problem of medication duplication in health care systems without gatekeeping or referral requirement. Thus, to overcome this problem, a reminder letter has been developed in Taiwan to nudge patients to engage in medication management.

OBJECTIVE

To evaluate the effect of reminder letter on reducing duplicated medications.

RESEARCH DESIGN

A 2-arm randomized controlled trial design.

SUBJECTS

Patients with duplicated medications in the first quarter of 2019.

MEASURES

The Taiwanese single-payer National Health Insurance Administration identified the eligible patients for this study. A postal reminder letter regarding medication duplication was mailed to the patients in the study group, and no information was provided to the comparison group. Generalized estimation equation models with a difference-in-differences analysis were used to estimate the effects of the reminder letters.

RESULTS

Each group included 11,000 patients. Those who had received the reminder letter were less likely to receive duplicated medications in the subsequent 2 quarters (postintervention 1: odds ratio [OR]=0.95, 95% CI=0.87-1.03; postintervention_2: OR=0.99, 95% CI=0.90-1.08) and had fewer days of duplicated medications (postintervention 1: β=-0.115, P =0.015; postintervention 2 (β=-0.091, P =0.089) than those who had not received the reminder letter, showing marginal but significant differences.

CONCLUSIONS

A one-off reminder letter nudge could mildly decrease the occurrence of duplicated medications. Multiple nudges or nudges incorporating behavioral science insights may be further considered to improve medication safety in health systems without gatekeeping.

How can a behavioral economics lens contribute to implementation science?

BACKGROUND

Implementation science in health is an interdisciplinary field with an emphasis on supporting behavior change required when clinicians and other actors implement evidence-based practices within organizational constraints. Behavioral economics has emerged in parallel and works towards developing realistic models of how humans behave and categorizes a wide range of features of choices that can influence behavior. We argue that implementation science can be enhanced by the incorporation of approaches from behavioral economics. Main body First, we provide a general overview of implementation science and ways in which implementation science has been limited to date. Second, we review principles of behavioral economics and describe how concepts from BE have been successfully applied to healthcare including nudges deployed in the electronic health record. For example, de-implementation of low-value prescribing has been supported by changing the default in the electronic health record. We then describe what a behavioral economics lens offers to existing implementation science theories, models and frameworks, including rich and realistic models of human behavior, additional research methods such as pre-mortems and behavioral design, and low-cost and scalable implementation strategies. We argue that insights from behavioral economics can guide the design of implementation strategies and the interpretation of implementation studies. Key objections to incorporating behavioral economics are addressed, including concerns about sustainment and at what level the strategies work.

CONCLUSION

Scholars should consider augmenting implementation science theories, models, and frameworks with relevant insights from behavioral economics. By drawing on these additional insights, implementation scientists have the potential to boost efforts to expand the provision and availability of high quality care.

Spillover effects of reminder nudges in complex environments

We present an experiment on the immediate and lasting effects of reminder nudges in a complex environment. In the study, 1,542 subjects face a setting where, within a brief time frame, they have to pay attention to and perform multiple actions in a computer game. The experiment investigates i) the effect of reminders on the reminded actions and their spillovers on nonreminded actions; ii) spillovers between multiple nudges when the number of reminded actions is increased; and iii) intertemporal spillovers from having been exposed to reminders on actions after reminders are withdrawn. Our findings reveal, first, that reminders have a positive effect on the overall number of actions performed. It results from the positive direct effect on the reminded actions dominating the negative spillovers on nonreminded actions. These negative effects are notable in our setting, where reminders could potentially have positive spillovers by freezing attention or by indirectly prompting actions similar to the reminded ones. Second, we observe that reminder nudges are scalable. Increasing the number of reminded actions leads subjects to take more actions overall, albeit with diminishing returns and more pronounced negative spillover effects. Third, after reminders are withdrawn, the positive effect on reminded actions diminishes, while negative spillovers on nonreminded actions persist, thus rendering reminders ineffective in increasing the overall number of actions performed.

Vaccination as personal public good provision

Vaccination against infectious diseases has both private and public benefits. We study whether social preferences-concerns for the well-being of other people-are associated with one's decision regarding vaccination. We measure these social preferences for 549 online subjects with a public-good game and an altruism game. To the extent that one gets vaccinated out of concern for the health of others, contribution in the public-good game is analogous to an individual's decision to obtain vaccination, while our altruism game provides a different measure of altruism, equity, and efficiency concerns. We proxy vaccine demand with how quickly a representative individual voluntarily took the initial vaccination for COVID-19 (after the vaccine was widely available). We collect COVID-19 vaccination history separately from the games to avoid experimenter-demand effects. We find a strong result: Contribution in the public-good game is associated with greater demand to voluntarily receive a first dose, and thus also to vaccinate earlier. Compared to a subject who contributes nothing, one who contributes the maximum ($4) is 58% more likely to obtain a first dose voluntarily in the four-month period that we study (April through August 2021). In short, people who are more pro-social are more likely to take a voluntary COVID-19 vaccination. Behavior in our altruism game does not predict vaccination. We recommend further research on the use of pro-social preferences to help motivate individuals to vaccinate for other transmissible diseases, such as the flu and HPV.

Testing the impact of differing behavioural science informed text message content in COVID-19 vaccination invitations on vaccine uptake: A randomised clinical trial

Behavioural science constructs can be incorporated into messaging strategies to enhance the effectiveness of public health campaigns by increasing the occurrence of desired behaviours. This study investigated the impact of behavioural science-informed text message strategies on COVID-19 vaccination rates in 18-39-year-olds in an area of low uptake in London during the first vaccination offer round in the United Kingdom. This three-armed randomised trial recruited unvaccinated residents of an urban Central London suburb being offered their first vaccination between May and June 2021. Participants were randomised to receive the control (current practice) text message or one of two different behavioural science-informed COVID-19 vaccine invitation strategies. Both intervention strategies contained the phrase "your vaccine is ready and waiting for you", aiming to evoke a sense of ownership, with one strategy also including a pre-alert message. The main outcome measures were vaccination rates at 3 and 8 weeks after message delivery. A total of 88,820 residents were randomly assigned to one of the three trial arms. Each arm had a vaccine uptake rate of 27.2 %, 27.4 % and 27.3 % respectively. The mean age of participants was 28.2 years (SD ± 5.7), the mean index of multiple deprivation was 4.3 (SD ± 2.0) and 50.4 % were women. Vaccine uptake varied by demographics, however there was no significant difference between trial arms (p = 0.872). Delivery was successful for 53.6 % of text messages. Our choice of behavioural science informed messaging strategies did not improve vaccination rates above the rate seen for the current practice message. This likely reflects the wide exposure to public health campaigns during the pandemic, as such text messages nudges were unlikely to alter existing informed decision-making processes. Text message delivery was relatively low, indicating a need for accurate mobile phone number records and multi-modal approaches to reach eligible patients for vaccination. The protocol was registered at clinicaltrials.gov (NCT04895683) on 20/05/2021.

Thinking about default enrollment lowers vaccination intentions and public support in G7 countries

Policymakers often face a conundrum between being transparent about policies and ensuring that those policies are effective. This challenge is particularly relevant for behavioral nudges, which are not usually disclosed. Rather than avoiding transparency, we suggest that policymakers encourage citizens to reflect on nudges to help them understand their own views and align those views with their behaviors. Using data from an online survey experiment with 24,303 respondents in G7 countries, we examine the impact of reflection on a hypothetical default nudge policy for COVID-19 booster appointments. Contrary to expectations, participants say they would be less likely to get the booster when automatically enrolled compared with a control condition. Similarly, encouraging citizens to think about the status quo (baseline) policy also reduces intentions for boosters. These interventions have no effect on approval of the policy. Further, encouraging people to think about automatic enrollment decreases approval of the policy and further decreases their intentions to get vaccinated. These findings suggest that reflection on a nudge can increase backlash from a nudge and also elicit policy disapproval, thereby aligning policy support with behavioral intentions.

Stress reduction experiments in daily life: Scaling from the lab to the world

Paced breathing-longer exhalation than inhalation-can show short-term improvement of physiologic responses and affective well-being, though most studies have relied on narrow sample demographics, small samples, and control conditions that fail to address expectancy effects. We addressed these limitations through an app-based experiment where participants were randomly assigned to paced breathing or sham control (hand closure) conditions. We first validated the conditions in an online sample (N = 201; Study 1) and in a lab environment (N = 72; Study 2). In the primary app-based experiment, participants (N = 3,277; Study 3) completed 3 days of baseline assessments that included three check-ins each day in which we obtained heart rate and blood pressure responses using an optic sensor and assessed current stress and emotions. Participants were then randomly assigned to either the paced breathing or hand closure condition for the next 6 days. Relative to baseline days, both conditions were associated with increased positive emotions and perceived coping, and reduced blood pressure. Moreover, the increase in positive emotions and perceived coping was not evident among a comparison sample (N = 2,600) who completed check-ins but did not participate in either of the paced breathing or sham-control conditions. However, their blood pressure declined over time, suggesting that the continual monitoring of one's blood pressure may result in detectable decreases. Our results highlight the importance of designing experiments with appropriately matched control conditions and suggest that changes associated with techniques like paced breathing, in part, may stem from positive incidental features of the technique. (PsycInfo Database Record (c) 2024 APA, all rights reserved).

Informational Postcards Increase Engagement with Remote Monitoring Among Veterans with Pacemakers and Implantable Cardioverter-Defibrillators: a Stepped-Wedge Randomized Controlled Trial

BACKGROUND

Remote monitoring (RM) of pacemakers and implantable cardioverter-defibrillators (ICDs) reduces morbidity and mortality. However, many patients are not adherent to RM.

OBJECTIVE

To test the effect of informational postcards on RM adherence.

DESIGN/PATIENTS

Stepped-wedge randomized controlled trial among Veterans with pacemakers and ICDs.

INTERVENTION

In wave 1, Veterans who had sent at least 1 transmission within the past 2 years but had become non-adherent were randomly assigned to receive a postcard or no postcard. Those receiving postcards were randomized to 1 of 2 messages: (1) a"warning" postcard describing risks of non-adherence or (2) an "encouraging" postcard describing benefits of adherence. In wave 2, Veterans who had either not received a postcard in wave 1 or had since become non-adherent were mailed a postcard (again, randomized to 1 of 2 messages). Patients who did not send an RM transmission within 1 month were mailed a second, identical postcard.

MAIN MEASURES

Transmission within 70 days.

KEY RESULTS

Overall, 6351 Veterans were included. In waves 1 and 2, postcards were mailed to 5657 Veterans (2821 "warning" messages and 2836 "encouraging" messages). Wave 1 included 2178 Veterans as controls (i.e., not mailed a postcard), some of whom received a postcard in wave 2 if they remained non-adherent. In wave 2, 3473 postcards were sent. Of the 5657 patients mailed a postcard, 2756 (48.7%) sent an RM transmission within 70 days, compared to 530 (24.3%) of 2178 controls (absolute difference 24.4%, 95% confidence interval [CI] 22.2%, 26.6%). Of those who sent a transmission, 71.8% did so after the first postcard. Transmission rates at 70 days did not significantly differ between "warning" and "encouraging" messages (odds ratio 1.04, 95% CI 0.92, 1.18).

CONCLUSIONS

Informational postcards led to a 24.4% absolute increase in adherence at 70 days among Veterans with pacemakers and ICDs who were non-adherent to RM.

Nudging a Nation - The Danish NUDGE Trial Concept

Danish NUDGE Trial ConceptRandomized encouragement trials randomize to an opportunity to receive treatment instead of to the treatment. Here, Johansen and colleagues combine randomized encouragement trials with several advantages inherent in the Danish health system.

Vaccine Nationalism Counterintuitively Erodes Public Trust in Leaders

Global access to resources like vaccines is key for containing the spread of infectious diseases. However, wealthy countries often pursue nationalistic policies, stockpiling doses rather than redistributing them globally. One possible motivation behind vaccine nationalism is a belief among policymakers that citizens will mistrust leaders who prioritize global needs over domestic protection. In seven experiments (total N = 4,215 adults), we demonstrate that such concerns are misplaced: Nationally representative samples across multiple countries with large vaccine surpluses (Australia, Canada, United Kingdom, and United States) trusted redistributive leaders more than nationalistic leaders-even the more nationalistic participants. This preference generalized across different diseases and manifested in both self-reported and behavioral measures of trust. Professional civil servants, however, had the opposite intuition and predicted higher trust in nationalistic leaders, and a nonexpert sample also failed to predict higher trust in redistributive leaders. We discuss how policymakers' inaccurate intuitions might originate from overestimating others' self-interest.

A megastudy on the predictability of personal information from facial images: Disentangling demographic and non-demographic signals

While prior research has shown that facial images signal personal information, publications in this field tend to assess the predictability of a single variable or a small set of variables at a time, which is problematic. Reported prediction quality is hard to compare and generalize across studies due to different study conditions. Another issue is selection bias: researchers may choose to study variables intuitively expected to be predictable and underreport unpredictable variables (the 'file drawer' problem). Policy makers thus have an incomplete picture for a risk-benefit analysis of facial analysis technology. To address these limitations, we perform a megastudy-a survey-based study that reports the predictability of numerous personal attributes (349 binary variables) from 2646 distinct facial images of 969 individuals. Using deep learning, we find 82/349 personal attributes (23%) are predictable better than random from facial image pixels. Adding facial images substantially boosts prediction quality versus demographics-only benchmark model. Our unexpected finding of strong predictability of iPhone versus Galaxy preference variable shows how testing many hypotheses simultaneously can facilitate knowledge discovery. Our proposed L1-regularized image decomposition method and other techniques point to smartphone camera artifacts, BMI, skin properties, and facial hair as top candidate non-demographic signals in facial images.

Crowdsourcing as a tool for creating effective nudges: An example for financial oversubscription

Creating effective nudges, or interventions that encourage people to make choices that increase their welfare, is difficult to execute well. Recent work on megastudies, massive field experiments that test many interventions simultaneously, reveals that nudge effectiveness both varies widely and is difficult for experts to predict. We propose an Iterative Crowdsourcing Procedure, which uses insights from members of the target population to generate and preselect nudges prior to testing them in a field experiment. This technique can supplement existing methods or stand alone as a way to generate conditions for testing in a high-quality field experiment. We test the effectiveness of this method in addressing a challenge to effective financial management: consumer oversubscription. We first document that people have more subscriptions than they think they have and that enhancing subscription awareness makes people want to cancel some subscriptions. We then use our crowdsourcing procedure to motivate people toward subscription awareness in a field experiment (N = 4,412,113) with a large bank. We find that the crowdsourced nudges outperform those generated by the bank, demonstrating that the Iterative Crowdsourcing Procedure is a useful way to generate effective nudges.

How does the vaccine approval procedure affect COVID-19 vaccination intentions?

People's willingness to vaccinate is critical to combating the COVID-19 pandemic. We devise a representative experiment to study how the design of the vaccine approval procedure affects trust in newly developed vaccines and consequently public attitudes towards vaccination. Compared to an Emergency Use Authorization, choosing the more thorough Conditional Marketing Authorization approval procedure increases vaccination intentions by 13 percentage points. The effects of the increased duration of the approval procedure are positive and significant only for Emergency Use Authorization. Treatment effects do not differ between relevant subgroups, such as respondents who had (did not have) COVID-19, or between vaccinated and unvaccinated respondents. Increased trust in the vaccine is the key mediator of treatment effects on vaccination intentions.

Nationwide Utilization of Danish Government Electronic letter system for increasing inFLUenza vaccine uptake (NUDGE-FLU): Study protocol for a nationwide randomized implementation trial

BACKGROUND

Annual influenza vaccination is widely recommended in older adults and other high-risk groups including patients with cardiovascular disease. The real-world effectiveness of influenza vaccination is limited by suboptimal uptake and effective strategies for increasing vaccination rates are therefore needed. The purpose of this trial is to investigate whether behavioral nudges digitally delivered via the Danish nationwide mandatory governmental electronic letter system can increase influenza vaccination uptake among older adults.

METHODS

The NUDGE-FLU trial is a randomized implementation trial randomizing all Danish citizens aged 65 years and above without an exemption from the Danish mandatory governmental electronic letter system to receive no digitally delivered behavioral nudge (usual care arm) or to receive one of 9 electronic letters (intervention arms) each leveraging different behavioral science strategies. The trial has randomized 964,870 participants with randomization clustered at the household level (n = 691,820 households). Intervention letters were delivered on September 16, 2022, and follow-up is currently ongoing. All trial data are captured using the nationwide Danish administrative health registries. The primary end point is the receipt of an influenza vaccine on or before January 1, 2023. The secondary end point is time to vaccination. Exploratory end points include clinical events such as hospitalization for influenza or pneumonia, cardiovascular events, all-cause hospitalization, and all-cause mortality.

DISCUSSION

The nationwide randomized NUDGE-FLU trial is one of the largest implementation trials ever conducted and will provide important insights into effective communication strategies to maximize vaccination uptake among high-risk groups.

TRIAL REGISTRATION

Clinicaltrials.gov: NCT05542004, registered September 15, 2022, https://clinicaltrials.gov/ct2/show/NCT05542004.

How to build up big team science: a practical guide for large-scale collaborations

The past decade has witnessed a proliferation of big team science (BTS), endeavours where a comparatively large number of researchers pool their intellectual and/or material resources in pursuit of a common goal. Despite this burgeoning interest, there exists little guidance on how to create, manage and participate in these collaborations. In this paper, we integrate insights from a multi-disciplinary set of BTS initiatives to provide a how-to guide for BTS. We first discuss initial considerations for launching a BTS project, such as building the team, identifying leadership, governance, tools and open science approaches. We then turn to issues related to running and completing a BTS project, such as study design, ethical approvals and issues related to data collection, management and analysis. Finally, we address topics that present special challenges for BTS, including authorship decisions, collaborative writing and team decision-making.

Fear of COVID-19 disease and vaccination as predictors of vaccination status

Vaccination rates are still insufficient to prevent the spread of COVID-19, so immunity must be increased among the population in order to reduce the virus' spread and the associated medical and psychosocial effects. Although previous work has identified various factors associated with a low willingness to get vaccinated, the role of emotions such as fear of vaccination (FVAC) or fear of COVID-19 (FCOV), vaccination as a subjective norm (SN), psychological factors like general control beliefs (CB) or psychological resilience, and their interaction have been investigated less intensively. We used data from three cross-sectional waves of the German Panel COSMO (November 2021, N = 1010; February 2022, N = 1026; March 2022, N = 1031) and multiple logistic regression analyses to test whether vaccination rates are moderated by those factors. After controlling for covariates (age, sex, confidence in own intuition, optimism, well-being), we found that CB was no significant predictor of vaccination status. Higher FCOV and higher ratings in SN, however, were associated with an increased likelihood of being vaccinated. In contrast, higher FVAC was associated with a decreased likelihood of being vaccinated. Psychological resilience did not consistently moderate the associations between fear and vaccination status.

Pharmacy-based immunization: a systematic review

Background

The coronavirus disease 2019 pandemic has prompted the exploration of new response strategies for such health contingencies in the near future. Over the last 15 years, several pharmacy-based immunization (PBI) strategies have emerged seeking to exploit the potential of pharmacies as immunization, medication sale, and rapid test centers. However, the participation of pharmacies during the last pandemic was very uneven from one country to another, suggesting a lack of consensus on the definition of their roles and gaps between the literature and practice.

Purpose

This study aimed to consolidate the current state of the literature on PBI, document its progress over time, and identify the gaps not yet addressed. Moreover, this study seeks to (i) provide new researchers with an overview of the studies on PBI and (ii) to inform both public health and private organization managers on the range of possible immunization models and strategies.

Methodology

A systematic review of scientific qualitative and quantitative studies on the most important scientific databases was conducted. The Preferred Reporting Items for Systematic Reviews and Meta-analyzes guidelines were followed. Finally, this study discusses the trends, challenges, and limitations on the existing literature on PBI.

Findings

Must studies concluded that PBI is a beneficial strategy for the population, particularly in terms of accessibility and territorial equity. However, the effectiveness of PBI is affected by the economic, political, and/or social context of the region. The collaboration between the public (government and health departments) and private (various pharmacy chains) sectors contributes to PBI's success.

Originality

Unlike previous literature reviews on PBI that compiled qualitative and statistical studies, this study reviewed studies proposing mathematical optimization methods to approach PBI.

Electronic nudges to increase influenza vaccination uptake in Denmark: a nationwide, pragmatic, registry-based, randomised implementation trial

BACKGROUND

Influenza vaccination rates remain suboptimal despite effectiveness in preventing influenza infection and related complications. We investigated whether behavioural nudges, delivered via a governmental electronic letter system, would increase influenza vaccination uptake among older adults in Denmark.

METHODS

We did a nationwide, pragmatic, registry-based, cluster-randomised implementation trial during the 2022-23 influenza season in Denmark. All Danish citizens aged 65 years or older or turning 65 years by Jan 15, 2023 were included. We excluded individuals living in nursing homes and individuals who had an exemption from the Danish mandatory governmental electronic letter system. Households were randomly assigned (9:1:1:1:1:1:1:1:1:1) to usual care or nine different electronic letters designed on the basis of different behavioural nudging concepts. Data were sourced from nationwide Danish administrative health registries. The primary endpoint was receipt of influenza vaccination on or before Jan 1, 2023. The primary analysis assessed an analytical set of one randomly selected individual per household, and a sensitivity analysis included all randomly assigned individuals and accounted for within-household correlation. The trial is registered with ClinicalTrials.gov, NCT05542004.

FINDINGS

We identified 1 232 938 individuals aged 65 years or older in Denmark and excluded 56 436 (4·6%) individuals living in nursing homes and 211 632 (17·2%) with an exemption from the electronic letter system. We randomly assigned 964 870 (78·3%) participants across 691 820 households. Compared with usual care, influenza vaccination rates were higher in the group receiving an electronic letter highlighting potential cardiovascular benefits of vaccination (81·00% vs 80·12%; difference 0·89 percentage points [99·55% CI 0·29-1·48]; p<0·0001) and the group receiving repeated letters at randomisation and at day 14 (80·85% vs 80·12%; difference 0·73 percentage points [0·13-1·34]; p=0·0006). These strategies improved vaccination rates across major subgroups including those with and without established cardiovascular disease. The cardiovascular gain-framed letter was particularly effective among participants who had not been vaccinated for influenza in the previous season (p_interaction=0·0002). A sensitivity analysis of all randomly assigned individuals accounting for within-household clustering yielded similar findings.

INTERPRETATION

Electronically delivered letters highlighting potential cardiovascular benefits of influenza vaccination or sent again as a reminder significantly increased vaccination uptake across Denmark. Although the magnitude of effectiveness was modest, the low-touch, inexpensive, and highly scalable nature of these electronic letters might be informative for future public health campaigns.

FUNDING

Sanofi.

Short Message Service Reminder Nudge for Parents and Influenza Vaccination Uptake in Children and Adolescents With Special Risk Medical Conditions: The Flutext-4U Randomized Clinical Trial

Importance

Children with chronic medical conditions are at increased risk of severe influenza. Uptake of influenza vaccination in children and adolescents with these identified special risk medical conditions (SRMCs) is suboptimal.

Objective

To assess the effectiveness of Flutext-4U, a parent short message service (SMS) reminder nudge intervention, in increasing influenza immunization in children and adolescents with SRMCs.

Design, Setting, and Participants

This randomized clinical trial was conducted at a tertiary pediatric hospital in Adelaide, South Australia, from April 15 to September 30, 2021. Children and adolescents aged 6 months to younger than 18 years with SRMCs and a subspecialist outpatient appointment over a 5-month period during the Australian seasonal influenza vaccination season (April-August 2021) were eligible to participate. Follow-up was until September 30, 2021.

Interventions

Participants were randomly assigned (1:1 ratio) to control: clinician nudges (hospital vaccine availability, ease of access, and recommendation from hospital subspecialists) or SMS intervention (control conditions plus an additional SMS reminder nudge to parents), with randomization stratified by age group (<5 years, 5-14 years, or >14 to <18 years).

Main Outcomes and Measures

The primary outcome was influenza vaccination, as confirmed by the Australian Immunisation Register.

Results

A total of 600 participants (intervention group: 298 [49.7%]; mean [SD] age, 11.5 [4.6] years; 162 female participants [54.4%]; control group: 302 [50.3%]; mean [SD] age, 11.4 [4.7] years; 155 female participants [51.3%]) were included. Influenza vaccination was 38.6% (113 of 293) in the SMS intervention group compared with 26.2% (79 of 302) in the control group (adjusted odds ratio [aOR], 1.79; 95% CI, 1.27-2.55; P = .001). Time to vaccine receipt was significantly lower among SMS participants (adjusted hazard ratio, 1.67; 95% CI, 1.25-2.22; P < .001). For participants randomly assigned by June 15, a significantly greater proportion receiving the SMS intervention were vaccinated during the optimal delivery period April to June 30 (SMS group: 40.0% [76 of 190] vs 25.4% [50 of 197]; aOR, 1.97; 95% CI, 1.28-3.06; P = .002).

Conclusions and Relevance

Results of this randomized clinical trial suggest that an additional SMS reminder nudge for parents delivered in the tertiary care hospital setting to children and adolescents with SMRCs resulted in higher influenza vaccine uptake compared with clinician nudges alone.

Trial Registration

ANZCTR Identifier: ACTRN12621000463875.

Megastudies: A New Approach to Reducing Vaccine Hesitation Worldwide

Vaccine hesitancy is a considerable obstacle to achieving vaccine protection worldwide. There needs to be more evidence-based research for interventions for vaccine hesitancy. Existing effectiveness evaluations are limited to one particular hypothesis, and no studies have compared the effectiveness of different interventions. A megastudy takes a large-scale, multi-intervention, uniform participant and the same evaluation criteria approach to evaluate many interventions simultaneously and find the most effective ones. Therefore, megastudies can help us find the most effective interventions for vaccine hesitancy. Additionally, considering the complex causes of vaccine hesitancy, we design interventions that involve social factors in megastudies. Lastly, quality control and justice are critical issues for megastudies in the future.

An Overview of Innovative Approaches to Support Timely and Agile Health Communication Research and Practice

Innovative approaches are needed to make health communication research and practice more timely, responsive, and effective in a rapidly changing information ecosystem. In this paper we provide an overview of strategies that can enhance the delivery and effectiveness of health communication campaigns and interventions, as well as research approaches that can generate useful data and insights for decisionmakers and campaign designers, thereby reducing the research-to-practice gap. The discussion focuses on the following approaches: digital segmentation and microtargeting, social media influencer campaigns, recommender systems, adaptive interventions, A/B testing, efficient message testing protocols, rapid cycle iterative message testing, megastudies, and agent-based modeling. For each method highlighted, we also outline important practical and ethical considerations for utilizing the approach in the context of health communication research and practice, including issues related to transparency, privacy, equity, and potential for harm.

A guide to megastudies

How can behavioral insights best be leveraged to solve pressing policy challenges? Because research studies are typically designed to test the validity of a particular idea, surprisingly little is known about the relative efficacy of different approaches to changing behavior in any given policy context. We discuss megastudies as a research approach that can surmount this and other obstacles to developing optimal behaviorally informed policy interventions. We define a megastudy as "a massive field experiment in which many different treatments are tested synchronously in one large sample using a common, objectively measured outcome." We summarize this apples-to-apples approach to research and lay out recommendations, limitations, and promising future directions for scholars who might want to conduct or evaluate megastudies.

Crowdsourcing interventions to promote uptake of COVID-19 booster vaccines

Background

COVID-19 booster vaccine uptake rates are behind the rate of primary vaccination in many countries. Governments and non-governmental institutions rely on a range of interventions aiming to increase booster uptake. Yet, little is known how experts and the general public evaluate these interventions.

Methods

We applied a novel crowdsourcing approach to provide rapid insights on the most promising interventions to promote uptake of COVID-19 booster vaccines. In the first phase (December 2021), international experts (n = 78 from 17 countries) proposed 46 unique interventions. To reduce noise and potential bias, in the second phase (January 2022), experts (n = 307 from 34 countries) and representative general population samples from the UK (n = 299) and the US (n = 300) rated the proposed interventions on several evaluation criteria, including effectiveness and acceptability, on a 5-point Likert-type scale.

Findings

Sanctions were evaluated as potentially most effective but least accepted. Evaluations by expert and general population samples were considerably aligned. Interventions that received the most positive evaluations regarding both effectiveness and acceptability across evaluation groups were: a day off work after getting vaccinated, financial incentives, tax benefits, promotional campaigns, and mobile vaccination teams.

Interpretation

The results provide useful insights to help governmental and non-governmental institutions in their decisions about which interventions to implement. Additionally, the applied crowdsourcing method may be used in future studies to retrieve rapid insights on the comparative evaluation of (health) policies.

Funding

This study received funding from the Austrian Science Fund (SFB F63) and the University of Vienna.

Vaccine Hesitancy: Contemporary Issues and Historical Background

Vaccination, despite being recognized as one of the most effective primary public health measures, is viewed as unsafe and unnecessary by an increasing number of individuals. Anxiety about vaccines and vaccination programs leading to vaccine hesitancy results from a complex mix of social and political influences, cultural and religious beliefs, the availability of and ability to interpret health and scientific information, and personal and population experiences of health systems and government policies. Vaccine hesitancy is becoming a serious threat to vaccination programs, and was identified as one of the World Health Organization’s top ten global health threats in 2019. The negative impact of anti-vaccination movements is frequently cited as one of the major reasons for rising vaccine hesitancy amongst the general public world-wide. This review discusses the various issues surrounding vaccine hesitancy and the anti-vaccine movement, starting with the definitions of vaccine hesitancy and the anti-vaccine movement in their early history and in the modern era, before discussing the key drivers of vaccine hesitancy, particularly across different regions of the world, with a focus on various countries with low-, middle-, or high-income economies with different socio-economic populations. The review concludes with the impact of vaccine hesitancy on herd immunity and social, psychological, and public health measures to counter vaccine hesitancy.

Nudging societally relevant behavior by promoting cognitive inferences

Effective behavioral interventions are essential to address urgent societal challenges. Over the past decade, nudging interventions (i.e., arranging the environment to promote adaptive behavioral choices) have surged in popularity. Importantly, effective application of the nudging approach requires clear guiding principles with a firm basis in behavioral science. We present a framework for nudging interventions that builds on evidence about the goal-directed inferential processes underlying behavior (i.e., processes that involve context-dependent inferences about goals and the actions available to achieve these goals). We used this framework to develop nudging interventions that target context-relevant cognitive inferences. We examined the effectiveness of these inference nudging interventions for promoting two important types of societal behavior: pro-environmental actions and adherence to COVID-19 guidelines. As predicted, two online studies revealed that inference nudging interventions successfully increased energy conservation (Study 1) as well as social distancing during the COVID-19 crisis (Study 2). A field experiment found that inference nudging interventions increased hand disinfection in a real-life store during the COVID-19 crisis (Study 3). Our findings highlight the importance of applying state-of-the-art insights about the (inferential) determinants of behavior in behavior change interventions.

Communicating doctors' consensus persistently increases COVID-19 vaccinations

The reluctance of people to get vaccinated represents a fundamental challenge to containing the spread of deadly infectious diseases1,2, including COVID-19. Identifying misperceptions that can fuel vaccine hesitancy and creating effective communication strategies to overcome them are a global public health priority3-5. Medical doctors are a trusted source of advice about vaccinations6, but media reports may create an inaccurate impression that vaccine controversy is prevalent among doctors, even when a broad consensus exists7,8. Here we show that public misperceptions about the views of doctors on the COVID-19 vaccines are widespread, and correcting them increases vaccine uptake. We implement a survey among 9,650 doctors in the Czech Republic and find that 90% of doctors trust the vaccines. Next, we show that 90% of respondents in a nationally representative sample (n = 2,101) underestimate doctors' trust; the most common belief is that only 50% of doctors trust the vaccines. Finally, we integrate randomized provision of information about the true views held by doctors into a longitudinal data collection that regularly monitors vaccination status over 9 months. The treatment recalibrates beliefs and leads to a persistent increase in vaccine uptake. The approach demonstrated in this paper shows how the engagement of professional medical associations, with their unparalleled capacity to elicit individual views of doctors on a large scale, can help to create a cheap, scalable intervention that has lasting positive impacts on health behaviour.

Minimal effects from injunctive norm and contentiousness treatments on COVID-19 vaccine intentions: evidence from 3 countries

Does information about how other people feel about COVID-19 vaccination affect immunization intentions? We conducted preregistered survey experiments in Great Britain (5,456 respondents across 3 survey waves from September 2020 to February 2021), Canada (1,315 respondents in February 2021), and the state of New Hampshire in the United States (1,315 respondents in January 2021). The experiments examine the effects of providing accurate public opinion information to people about either public support for COVID-19 vaccination (an injunctive norm) or public beliefs that the issue is contentious. Across all 3 countries, exposure to this information had minimal effects on vaccination intentions even among people who previously held inaccurate beliefs about support for COVID-19 vaccination or its perceived contentiousness. These results suggest that providing information on public opinion about COVID vaccination has limited additional effect on people's behavioral intentions when public discussion of vaccine uptake and intentions is highly salient.

A 680,000-person megastudy of nudges to encourage vaccination in pharmacies

Encouraging vaccination is a pressing policy problem. To assess whether text-based reminders can encourage pharmacy vaccination and what kinds of messages work best, we conducted a megastudy. We randomly assigned 689,693 Walmart pharmacy patients to receive one of 22 different text reminders using a variety of different behavioral science principles to nudge flu vaccination or to a business-as-usual control condition that received no messages. We found that the reminder texts that we tested increased pharmacy vaccination rates by an average of 2.0 percentage points, or 6.8%, over a 3-mo follow-up period. The most-effective messages reminded patients that a flu shot was waiting for them and delivered reminders on multiple days. The top-performing intervention included two texts delivered 3 d apart and communicated to patients that a vaccine was "waiting for you." Neither experts nor lay people anticipated that this would be the best-performing treatment, underscoring the value of simultaneously testing many different nudges in a highly powered megastudy.

Impact of information framing and vaccination characteristics on parental COVID-19 vaccine acceptance for children: a discrete choice experiment

This study aimed to test the influence of vaccination characteristics and gain/loss-framing of information, on parental acceptance of the coronavirus disease 2019 (COVID-19) vaccination for their minor children. A discrete choice experiment was conducted among parents of children aged 0-17 years from September to October 2021 in Hong Kong. Respondents were randomly assigned to four groups with different framing of information and asked to choose hypothetical vaccination alternatives, described by seven attributes that were derived from prior qualitative interviews. A mixed logit model was adopted to analyze the effect of attributes and information framing on parental vaccination acceptance. The vaccine acceptance rates under different scenarios were also estimated. A total of 298 valid responses were obtained. It was found that the BioNTech brand, higher efficacy, less serious adverse events and more vaccination coverage in children significantly improved parental acceptance. Additionally, loss-framing increased parental acceptance compared with gain-framing, while the presentation of mortality information did not make a difference. Acceptance was also associated with parental uptake of the COVID-19 vaccine and the children's age.

CONCLUSION

The findings imply that factors including gain/loss information framing, importance of vaccine characteristics, and peer influence have a significant effect on parents' decisions to get their children vaccinated. Parents with younger children had greater vaccine hesitancy, and information framing techniques should be considered in vaccination promotion for combating such vaccine hesitancy. Future studies could be conducted to identify the moderators and mediators of information framing to facilitate its implementation.

WHAT IS KNOWN

• Parental acceptance of COVID-19 vaccine was found to be associated with various socio-economic and psychosocial factors, while the evidence on impact of vaccination characteristics was limited. • Behavioral interventions, including information framing, have been used to promote various health behaviors.

WHAT IS NEW

• Loss-framing of information on vaccine effectiveness improves vaccine acceptance, while additional information on how the vaccine reduces death does not make a difference, which can be used to inform communication with the public in vaccination promotion. • The social norm (i.e., the vaccine uptake amongst other people) is important for increasing the parental vaccine acceptance rate.