Adult immunization is a critical yet underdeveloped area within European public health, as fragmented systems and implementation barriers persist. With a growing burden of vaccine-preventable diseases among adults due to demographic aging and emerging pathogens, this policy comment aims to address key barriers impeding a high vaccination uptake, including data availability, feasibility issues, political and financial constraints, vaccine confidence and literacy among the population and healthcare providers, and access issues and organization. Drawing on insights from Adult Immunization Board (AIB) meetings and discussions, a decalogue of actionable policy recommendations is proposed to overcome these barriers. This comprehensive strategy underscores the need for coordinated, multidisciplinary efforts and sustained political commitment to optimize adult immunization programs, leveraging lessons from the recent COVID-19 pandemic response.

Social media is a critical platform for understanding and fostering public engagement with health interventions. However, the lack of real-time social media infoveillance on public health issues may lead to delayed responses and suboptimal policy adjustments. To address this gap, we developed PH-LLM—a novel suite of large language models (LLMs) designed for real-time public health monitoring. We curated a multilingual training corpus and trained PH-LLM using QLoRA and LoRA plus, leveraging Qwen 2.5. We constructed a benchmark comprising 19 English and 20 multilingual held-out tasks and evaluated PH-LLM’s zero-shot performance. PH-LLM consistently outperformed baseline LLMs of similar and larger sizes. PH-LLM-14B and PH-LLM-32B surpassed Qwen2.5-72B-Instruct, Llama-3.1-70B-Instruct, Mistral-Large-Instruct-2407, and GPT-4o in both English tasks (>=56.0% vs. <= 52.3%) and multilingual tasks (>=59.6% vs. <= 59.1%). PH-LLM represents a significant advancement in real-time public health infoveillance, offering state-of-the-art multilingual capabilities and cost-effective solutions for monitoring public sentiment on health issues.

Vaccine confidence—the trust individuals place in the safety, efficacy, and importance of vaccines—is waning globally. Digital platforms, algorithmic content curation, and generative artificial intelligence have fundamentally altered how people encounter information and what they believe to be true. In this commentary, the authors argue that rebuilding vaccine confidence requires a strategic reorientation that centers on technology as both the source of risk and the site of potential remedy. By foregrounding platform design, algorithmic transparency, and AI governance, we can begin to imagine a future where digital technologies support, rather than subvert, public health.

mRNA vaccines represent a transformative advance in vaccinology, combining rapid development timelines, scalable manufacturing, and strong immunogenicity with a favourable safety profile. Global deployment of mRNA vaccines during the COVID-19 pandemic provided an unprecedented real-world evaluation of this platform, with billions of doses administered across diverse populations. In this Review, we critically examine the safety and efficacy of mRNA vaccines from mechanistic, preclinical, clinical, and public health perspectives. We outline the biological basis of mRNA vaccines, including their transient cytoplasmic expression, lack of genomic integration, and rapid clearance, distinguishing them clearly from other gene therapies. We synthesise evidence on vaccine components, manufacturing quality controls, and regulatory standards that underpin safety, alongside data from randomised trials, post-authorisation surveillance, and active pharmacovigilance systems. We also review real-world effectiveness across age groups, pregnancy, and populations that are immunocompromised, along with the effects on transmission. Last, we address public perception and vaccine confidence, and discuss implications for next-generation mRNA vaccines, including strategies to reduce reactogenicity, improve breadth and durability of immunity, enhance global access, and support sustainable public trust. Together, the accumulated evidence affirms mRNA vaccines as a safe, effective, and adaptable platform with enduring relevance for future infectious disease prevention and public health preparedness, and for the treatment of cancer and autoimmunity.

BackgroundDespite early success in COVID-19 vaccine rollout, several East Asian countries have seen declining uptake of annual COVID-19 vaccination among adults since 2022. Through a comparative lens, we examine vaccine confidence, trusted information sources, and mRNA vaccine acceptance in four super-ageing societies. MethodsWe analysed nationally representative Global Listening Project survey data from Japan, South Korea, Taiwan, and Hong Kong (2023; n=1,000 participants per region) and a Tokyo deep-dive survey (2024; n=5,050). We compared institutional trust, trusted voices, vaccine safety and perceptions, and mRNA awareness and mRNA vaccine acceptance across demographic groups. We pair descriptive results with contemporary vaccination policy contexts. FindingsA high-uptake/low-confidence paradox emerged around COVID-19 vaccination uptake, exceeding 80% across settings, while confidence in vaccine safety ranged from 51% in Japan to 68% in Taiwan. Consistent gender and generational divides exist: men and older adults’ express higher confidence than women and younger groups. Family members, doctors, and local governments were widely trusted while national governments less so. Older adults relied on television, and younger groups turned to social media for trusted information. Knowledge of mRNA vaccines was limited, even among healthcare professionals. Acceptance of a new mRNA vaccine was highest in Taiwan (78%) and lowest in Japan (56%), with men more accepting than women. InterpretationsTailored communication that leverages local trust networks, addresses cultural, gender-specific concerns and accounts for the influential role of family members and doctors, is essential to build vaccine confidence in routine vaccine programs as well as for pandemic preparedness. Policies should reinforce recommendations and reminder systems (e.g., SMS recall), while simultaneously addressing cost and access barriers for older adults. Integrating gender- and age-specific trust-building measures into immunisation policy and crisis planning is needed.

BackgroundSeasonal influenza has an estimated global reach of 3-5 million infections, with 290,000-650,000 influenza-related deaths yearly. Despite its efficacy in reducing morbidity and mortality, influenza vaccination rates remain low globally and in South Africa. Youth between the ages of 18 and 34 years are not prioritized for influenza vaccines although influenza surveillance in South Africa shows that individuals aged 19-44 years present the highest asymptomatic episodes and the lowest medically attended illness. This creates an opportunity to investigate if and how vaccine demand can be created in the absence of clear imperatives to vaccinate. The study tests the effectiveness of tailored, context-specific education, and community engagement, including community and social media to increase influenza vaccination uptake. Tailored, context-specific education, community engagement, reliable vaccine supply, and free, localized access are all critical for improving perceptions of, increasing confidence in, and motivating the uptake of vaccination. ObjectiveThis study will explore strategies to increase influenza vaccine uptake amongst economically marginalized youth aged 18-34 years in Soweto (South-Western Townships), South Africa, where influenza vaccines are not universally accessible through the public health system for this age group. MethodsThe Bambisana Study uses an innovative approach, including community influencers and social media to increase the uptake of influenza vaccines through designing and testing an integrated communications strategy targeted at economically marginalized youth in Soweto, South Africa. The study uses a mixed methods pretest-posttest intervention design to test the effects of the interventions. The intervention will consist of the following components: (1) social media campaign, (2) microinfluencers on and offline, and (3) nonsocial media focused, offline microinfluencer-led engagement within communities. Quantitative data will be collected using a randomized household sample pre- and posttests, and clinic surveys with vaccinees and clinic attendees who declined vaccination. Focus group discussions (FGDs) will be conducted pre- and post intervention with participants aged ≥18 years, and 20 key informant interviews (KIIs) will be conducted with key influencers including religious leaders, traditional healers, and youth leaders. FGDs and KIIs will be audio-recorded and transcribed into English for analysis using framework thematic analysis, and quantitative data analyses will be conducted using SAS Enterprise (Guide 7.15; SAS Institute). ResultsThis study was funded in December 2022, with recruitment having started in May 2023. As of May 2024, all data collection is complete, with data analyses and preparation of peer-reviewed publications in progress. The first results are expected to be submitted for publication in November 2024. ConclusionsEnhancing perceptions of, bolstering confidence in, and fostering uptake of vaccination relies heavily on the efficacy of yearly influenza vaccination initiatives, personalized education tailored to specific contexts, active community involvement, consistent vaccine availability, and easily accessible, cost-free distribution channels at the local level. International Registered Report Identifier (IRRID)DERR1-10.2196/60481

BACKGROUND:Influenza vaccination coverage in South Africa is less than 3 % among the general adult population. We explored factors associated with influenza vaccine uptake using the World Health Organization's Strategic Advisory Group on Immunization (SAGE) 3C (confidence, complacency, convenience) model of vaccine hesitancy. METHODS:The present study forms part of the Bambisana project, a mixed-methods pre-test-post-test intervention study conducted from 29 April 2023 to 15 April 2024. Participants ≥18 years were enrolled in six Focus Group Discussions (FGDs), stratified by age (≥18-34 and ≥ 35 years). FGDs were audio-recorded, transcribed verbatim, and coded in Dedoose using framework analysis. RESULTS:Among the 48 participants, most (66.7 %, n = 30) were aged 18-34 years, 65.9 % (n = 29) had completed high school, and 70.2 % (n = 33) were unemployed. Overall, influenza vaccine uptake was associated with three key factors: low confidence, high complacency, and a lack of convenience. Low confidence in the influenza vaccine was associated with negative experiences with COVID-19 vaccines, fear of side effects, vaccine misconceptions, fear of needles, mistrust of public health institutions, and concerns about vaccine effectiveness. Complacency factors included reliance upon traditional and alternative medicines, lack of knowledge about vaccines, and minimising the seriousness of influenza illness. Convenience factors included perceived costs of the vaccine and a lack of influenza vaccine promotion. CONCLUSION:Addressing confidence, complacency and convenience factors is important to increase influenza vaccine acceptance and uptake in South Africa.

Vaccine hesitancy seriously compromised the COVID-19 vaccine roll-out across the Western Pacific with limited evidence-based recommendations for diverse populations across the region. This study investigates the profile of the vaccine-hesitant populations by using fixed-effect latent class analysis and multi-country survey data collected in 12 countries in 2021 and 2022: Cambodia, Viet Nam, Lao PDR, Japan, Republic of Korea, Malaysia, Philippines, Mongolia, Fiji, Solomon Islands, Tonga and Vanuatu. The analysis identified 9 latent classes: Stay-at-home mothers, High-school-educated employees, High-school-educated older adults, High-school-educated young adults, University-educated employees, University-educated older adults, University-educated young adults, Unemployed, Non-compliant employees. The probabilities of COVID-19 vaccine acceptance and booster uptake were significantly lower in most of these latent classes, compared to University-educated older adults, as the reference group. While each country had unique compositions of latent classes among vaccine-hesitant people, there were also some shared risk groups, such as High-school-educated employees and High-school-educated young adults, across the countries. The study findings demonstrate the benefits of subgroup analysis in unpacking the complex interplay of characteristics within vaccine-hesitant populations, highlighting the need for customised strategies tailored to each country’s unique profile of vaccine hesitancy.

Pediatric solid organ transplant candidates and recipients remain undervaccinated and at higher risk of vaccine preventable illness (VPI) than the general population. An American Society of Transplantation Pediatric Community of Practice Controversies Conference was held in October 2023 to discuss opportunities to improve vaccine uptake and decrease rates of VPI in this population. Undervaccination results from failures at different levels. Clinician misconceptions about when vaccines may be contraindicated often lead to delays, and vaccines recommended by the Advisory Committee on Immunization Practices may not be readily available in subspecialty clinics involved in transplant care. Lack of linked electronic vaccine tracking and effective messaging also undermine vaccine administration efforts in this vulnerable population. While access and availability barriers along with provider knowledge gaps are important reasons for undervaccination in this population, vaccine hesitancy and refusal also can cause significant challenges. We suggest an individualized approach that prioritizes education and counseling about VPIs and vaccination in pediatric solid organ transplant candidates and recipients while still respecting parental autonomy within the clinician-patient-parent relationship.

It has often been argued that trust cannot be built during crises. While this line of thinking recognizes the importance of building trust before or after crises, it negates the possibility of building trust during a crisis. This paper offers two scenarios to argue for the possibilities of building trust during crises by engaging with existing distrust, with special reference to examples during the COVID-19 pandemic. The first considers distrust towards vaccines and public health interventions among Black Americans that was addressed through interventions that partnered with trusted third parties during the COVID-19 pandemic. The second discusses the Indian transgender community where trust networks built between public health organizations and activists groups was mobilized to engage with existing distrust during the COVID-19 pandemic. Despite the success of these interventions, this perspective paper ends by clarifying that engaging with distrust does not have to result in achieving public health goals with a brief considerations of two cases: the polio vaccine boycott in Nigeria (2003) and medical populism in the United States during the COVID-19 pandemic. These examples highlight that if existing distrust toward the medical system is not addressed, then space is created during crises-periods for distrust to be mobilized in ways that compromise public health goals.

Pandemic preparedness necessitates a multifaceted approach that emphasizes societal factors, such as building trust and acknowledges cultural and societal differences, with a focus on protecting vulnerable groups. To support these goals, the European Global Health Research Institutes Network has outlined a comprehensive transdisciplinary approach through a set of multilevel recommendations.

Background:Catch-up HPV vaccination is challenging in many low and middle-income countries (LMICs). Pay-it-forward offers an individual a subsidized vaccine, then an opportunity to donate to help others access vaccinations. Our randomized control trial assessed the effectiveness of pay-it-forward in improving HPV vaccination among girls aged 15-18 years in China. Methods and findings:Eligible participants were randomly assigned to either the pay-it-forward arm or standard-of-care arm (self-paid vaccination). The primary outcome was the first-dose HPV vaccination rate, verified against clinical records. Among 321 participants enrolled, most caregivers were female (80.1%). In the pay-it-forward arm, 55 of 161 (34.2%) girls received the HPV vaccine, compared with 28 of 160 (17.5%) girls in the standard-of-care arm (adjusted proportion difference = 17.9%, 95% CI: 8.7, 27.0, P<0.001). Among 55 girls in the pay-it-forward arm who received the vaccination, 37 (67.3%) wrote a postcard message, and 39 (70.9%) of their caregivers donated to support future girls. The financial cost per person vaccinated was $294 in the standard-of-care arm and $230 in the pay-it-forward arm. Conclusions:The pro-social pay-it-forward strategy was effective to increase catch-up HPV vaccination among teenage girls with comparable costs. Trial registration:ChiCTR2200055542.

BACKGROUND:This study aimed to identify drivers of HPV vaccine hesitancy and effective public health interventions to increase HPV vaccination rates in two U.S. states (New York and Florida) and 12 counties within each state. The findings provide insights into the impact of demographics, state policies, and vaccine confidence on HPV vaccination. METHODS:We utilized a mixed-method approach, integrating quantitative analysis of county-level surveys, qualitative interviews, and secondary data on HPV vaccine coverage. Surveys, adapted from the Vaccine Confidence Project (VCP) and the World Health Organization (WHO), assessed HPV vaccine confidence, socio-demographics, and behavioral determinants. Interviews explored barriers, interventions, and policies related to HPV vaccination. FINDINGS:Parents and providers have not prioritized HPV vaccination compared to other vaccines, with less concern about HPV than other vaccine-preventable diseases. Socio-demographic factors, such as race, age, gender, religion, employment, and income impacted children's vaccination status. Female parents aged 35-44 and those with a professional degree were more likely to vaccinate their children. Perceptions of the vaccine's importance and safety significantly influenced vaccination. INTERPRETATION:Identifying socio-demographic determinants and behavioral motivators can guide targeted interventions. Our study highlights complex factors influencing HPV vaccination at the state and county level, offering policymakers strategies to tailor interventions addressing barriers and hesitancy in areas with lower vaccination rates.

Despite significant public health attention and investment, hundreds of thousands of individuals have suffered fatal opioid overdose since the onset of the opioid crisis. Risk of opioid overdose has been exacerbated by the influx of fentanyl, a powerful synthetic opioid, into the drug supply. The National Institutes of Health Helping End Addiction Long-term (HEAL) Initiative is supporting the development of vaccines targeting fentanyl to protect against overdose. If successful, a vaccine would induce anti-fentanyl antibodies to sequester fentanyl (but not other opioids) in the blood, preventing fentanyl from crossing into the brain and reaching the central nervous system where it can cause overdose. Introduction of an overdose preventing strategy that relies on a vaccine to confer passive protection may be impactful. However, vaccines are poorly understood by the public and politicized. Moreover, the overdose ecosystem is complex and extends across numerous social, economic, medical, and cultural systems. As such, optimal use of a vaccine strategy to address overdose may benefit from multidisciplinary consideration of the social, ethical, and systemic factors that influence substance use and overdose that may also impact the acceptability of a fentanyl vaccine and related implementation strategies.In March 2022, Dr. Elissa Weitzman convened a two-day conference at the Harvard Radcliffe Institute for Advanced Study on the Social Complexity of a Fentanyl Vaccine to Prevent Opioid Overdose. In all, 19 professionals from diverse disciplines (medicine, psychology, history, ethics, immunology, vaccinology, communications, policy) attended the conference and led discussions that centered on population health and epidemiology, history of medicine and frameworks for understanding substance use, ethics, decision-making and attitudes, and operational issues to the question of a novel immunotherapy targeting fentanyl overdose. Participants also debated the risks and benefits of vaccine administration in response to fictional clinical case vignettes. A summary of the conference presentations and discussions follows.

Conversational artificial intelligence, in the form of chatbots powered by large language models, offers a new approach to facilitating human-like interactions, yet its efficacy in enhancing vaccination uptake remains under-investigated. This study assesses the effectiveness of a vaccine chatbot in improving human papillomavirus (HPV) vaccination among female middle school students aged 12-15 years across diverse socioeconomic settings in China, where HPV vaccination is primarily paid out-of-pocket. A school-based cluster randomized trial was conducted from 18 January to 31 May 2024. The study included 2,671 parents from 180 middle school classes stratified by socioeconomic setting, school and grade level in Shanghai megacity, and urban and rural regions of Anhui Province. Participants were randomly assigned to either the intervention group (90 classes, 1,294 parents), which engaged with the chatbot for two weeks, or the control group (90 classes, 1,377 parents), which received usual care. The primary outcome was the receipt or scheduled appointment of the HPV vaccine for participants' daughters. In intention-to-treat analyses, 7.1% of the intervention group met this outcome versus 1.8% of the control group (P < 0.001) over a two-week intervention period. In addition, there was a statistically significant increase in HPV vaccination-specific consultations with health professionals (49.1% versus 17.6%, P < 0.001), along with enhanced vaccine literacy (P < 0.001) and rumor discernment (P < 0.001) among participants using the chatbot. These findings indicate that the chatbot effectively increased vaccination and improved parental vaccine literacy, although further research is necessary to scale and sustain these gains. Clinical trial registration: NCT06227689.

Background:The effectiveness of public health intervention, such as vaccination and social distancing, relies on public support and adherence. Social media has emerged as a critical platform for understanding and fostering public engagement with health interventions. However, the lack of real-time surveillance on public health issues leveraging social media data, particularly during public health emergencies, leads to delayed responses and suboptimal policy adjustments. Methods:To address this gap, we developed PH-LLM (Public Health Large Language Models for Infoveillance)-a novel suite of large language models (LLMs) specifically designed for real-time public health monitoring. We curated a multilingual training corpus comprising 593,100 instruction-output pairs from 36 datasets, covering 96 public health infoveillance tasks and 6 question-answering datasets based on social media data. PH-LLM was trained using quantized low-rank adapters (QLoRA) and LoRA plus, leveraging Qwen 2.5, which supports 29 languages. The PH-LLM suite includes models of six different sizes: 0.5B, 1.5B, 3B, 7B, 14B, and 32B. To evaluate PH-LLM, we constructed a benchmark comprising 19 English and 20 multilingual public health tasks using 10 social media datasets (totaling 52,158 unseen instruction-output pairs). We compared PH-LLM's performance against leading open-source models, including Llama-3.1-70B-Instruct, Mistral-Large-Instruct-2407, and Qwen2.5-72B-Instruct, as well as proprietary models such as GPT-4o. Findings:Across 19 English and 20 multilingual evaluation tasks, PH-LLM consistently outperformed baseline models of similar and larger sizes, including instruction-tuned versions of Qwen2.5, Llama3.1/3.2, Mistral, and bloomz, with PH-LLM-32B achieving the state-of-the-art results. Notably, PH-LLM-14B and PH-LLM-32B surpassed Qwen2.5-72B-Instruct, Llama-3.1-70B-Instruct, Mistral-Large-Instruct-2407, and GPT-4o in both English tasks (>=56.0% vs. <=52.3%) and multilingual tasks (>=59.6% vs. <= 59.1%). The only exception was PH-LLM-7B, with slightly suboptimal average performance (48.7%) in English tasks compared to Qwen2.5-7B-Instruct (50.7%), although it outperformed GPT-4o mini (46.9%), Mistral-Small-Instruct-2409 (45.8%), Llama-3.1-8B-Instruct (45.4%), and bloomz-7b1-mt (27.9%). Interpretation:PH-LLM represents a significant advancement in real-time public health infoveillance, offering state-of-the-art multilingual capabilities and cost-effective solutions for monitoring public sentiment on health issues. By equipping global, national, and local public health agencies with timely insights from social media data, PH-LLM has the potential to enhance rapid response strategies, improve policy-making, and strengthen public health communication during crises and beyond. Funding:This study is supported in part by NIH grants R01LM013337 (YL).