Heidi J Larson

• PhD
• Professor at London School of Hygiene and Tropical Medicine and Unversity of Washington (Seattle)

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 dist...

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 a...

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 coun...

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...

For too long, the theory and practice of infectious disease outbreak response has been the domain of a small number of experienced responders. The COVID-19 pandemic brought global attention to the requirements of effective outbreak response, and the need for preparation across the key pillars. Decisionmakers, early career practitioners and those in...

The rapid advancement of digital health technologies has heightened demand for health data for secondary uses, highlighting the importance of understanding global perspectives on personal information sharing. This article examines stakeholder perceptions and attitudes toward the use of personal health data to improve personalized treatments, interv...

The development and rollout of mRNA vaccines during COVID-19 marked a significant advancement in vaccinology, yet public hesitation to vaccination was prevalent, indicating the potential risk that future mRNA-based medical innovations will fail to be adopted. Utilizing a combined approach of large language models with manual validation and unsuperv...

Background In the midst of the global COVID-19 vaccine distribution challenge, religion stands out as a key determinant of vaccine hesitancy and health choices. Notably, the multifaceted religious environments of Africa and the Asia Pacific remain under-researched in this context. Methods Utilizing data from two survey waves conducted between 2021...

Trust is fundamental to cooperation, essential in times of crisis. Researching and understanding trust networks and perceptions of trustworthiness is therefore crucial in preparing for future health shocks, write Heidi Larson and colleagues

Background COVID-19 protective behaviors are key interventions advised by the World Health Organization (WHO) to prevent COVID-19 transmission. However, achieving compliance with this advice is often challenging, particularly among socially vulnerable groups. Objective We developed a social vulnerability index (SVI) to predict individuals’ propens...

It is unclear how great a challenge pandemic and vaccine fatigue present to public health. We assessed perspectives on coronavirus disease 2019 (COVID-19) and routine immunization as well as trust in pandemic information sources and future pandemic preparedness in a survey of 23,000 adults in 23 countries in October 2023. The participants reported...

Background Herpes Zoster is an age dependent disease and as such it represents a problem in the Italian social context, where the demographic curve is characterized by an overrepresentation of the elderly population. Vaccines against Herpes Zoster are available, safe and effective, however coverage remains sub-optimal. This study was therefore cond...

Background Accurate assessments of current and future fertility-including overall trends and changing population age structures across countries and regions-are essential to help plan for the profound social, economic, environmental, and geopolitical challenges that these changes will bring. Estimates and projections of fertility are necessary to i...

Influenza is a significant public health concern, with Italy being profoundly impacted annually. Despite extensive vaccination campaigns and cooperative initiatives between the Public Health Departments of Local Healthcare Authorities and family physicians, low vaccine uptake rates persist. This study builds upon the OBVIOUS project, providing an u...

Introduction The World Health Organization defines rotavirus as among the most severe causes of viral gastroenteritis affecting children under 5 year old. Italy and other European countries do not release disaggregated data on rotavirus vaccination coverage. This study aimed to assess the uptake and drivers of rotavirus vaccination in Italy. Metho...

Background Streptococcus pneumoniae infections, including Invasive Pneumococcal Diseases (IPDs), pose a substantial public health challenge, causing significant morbidity and mortality, especially among children and older adults. Vaccination campaigns have played a vital role in reducing pneumococcal-related deaths. However, obstacles related to ac...

Childhood influenza vaccination coverage remains low in lower/middle-income countries. This systematic review aims to identify influencing factors around childhood influenza vaccination. A systematic literature review was conducted and included empirical studies with original data that investigated factors influencing childhood influenza vaccinatio...

Background: Human Papillomavirus (HPV) vaccination rates are still below the target due to vaccine refusal or delay, lack of knowledge, and logistical challenges. Understanding these barriers is crucial for developing strategies to improve HPV vaccination rates. Methods: This cross-sectional study used a questionnaire to investigate social and beha...

Background COVID-19 vaccines effectively reduced the severity of the pandemic, but the mass rollout was challenged by vaccine hesitancy, which was related to heterogenous factors—such as religiosity, mistrust, and a lack of scientific knowledge—around the globe. Distinguishing these potential influencers and quantifying their impacts would help aut...

Artificial intelligence has potential to counter vaccine hesitancy while building trust in vaccines, but it must be deployed ethically and responsibly, argue Heidi Larson and Leesa Lin

Background Adolescent girls in China have a low HPV vaccination rate. Although vaccination is recommended by the Chinese health authorities, the cost is not covered by the national immunisation programme. Vaccination delay, among other reasons such as supply shortage and poor affordability, may contribute to low uptake. This sequential mixed method...

Vaccine hesitancy is an age-long phenomenon, with a growing trend in the modern scientific world. It became more evident during the COVID-19 pandemic as many individuals are not willing to take the COVID-19 vaccine. Convincing those who are vaccine-hesitant is difficult, but doing so is critical to bring the pandemic under control globally. This ch...

Objective To assess spatiotemporal trends in, and determinants of, the acceptance of coronavirus disease 2019 (COVID-19) vaccination globally, as expressed on the social media platform X (formerly Twitter). Methods We collected over 13 million posts on the platform regarding COVID-19 vaccination made between November 2020 and March 2022 in 90 lang...

Introduction A Chinese clinical trial has demonstrated that a prosocial pay-it-forward intervention that offered subsidized vaccination and postcard messages effectively increased influenza vaccine uptake and vaccine confidence. This secondary analysis explored the potential mediating role of vaccine confidence on the association between a pay-it-f...

The Covid pandemic has yielded new insights into psychological vaccine acceptance factors. This knowledge serves as a basis for behavioral and communication interventions that can increase vaccination readiness for other diseases.

BACKGROUND COVID-19 protective behaviors are key interventions advised by the World Health Organization (WHO) to prevent COVID-19 transmission. However, achieving compliance with this advice is often challenging, particularly among socially vulnerable groups. OBJECTIVE We developed a social vulnerability index (SVI) to predict individuals’ propens...

Background The 2018 Changchun Changsheng vaccine incident is an emergent public health event in China with reports of DTaP vaccines with compromised efficacy. This study aimed to estimate the impact of the vaccine incident on real-world vaccination behaviors in China. Methods A cross-sectional survey was conducted in ten provinces in 2019. Vaccina...

Many public health initiatives encouraging positive health behaviours require patient cooperation in the face of perceived costs and health risks. Ongoing public health crises, including the COVID-19 pandemic and the organ shortage, underscore the necessity of incorporating an understanding of human cooperation and the motivators for cooperation in...

The COVID-19 pandemic has disrupted societies globally. Public health insti-tutions were tasked with responding to the pandemic in a dynamic and uncertain context. This paper sheds light on the experiences of COVID-19 response actors as they navigated multi-dimensional crises associated with the pandemic in general and vaccine hesitancy in particul...

Introduction Influenza vaccination uptake among young children has been poor in China, but it is unclear how it changed during the COVID-19. This study aimed to investigate the uptake status and reasons of childhood influenza vaccination during the pandemic in China. Methods A mixed-methods study combining a questionnaire survey and semi-structure...

Declining trends in vaccine confidence come at a time when routine immunization coverage for children has slumped to a decades-long low. With some of the largest losses in confidence experienced among young adults, this is a concerning trend with the potential for long-term implications. This article reflects on recent research examining the levels...

Influenza annually claims an estimated 8,000 lives in Italy. Despite no-cost vaccinations for high-risk groups, hesitancy persists. This study aims to pinpoint social and behavioral vaccination determinants, forming strategies to bolster vaccine uptake. From April 11 to May 29, 2022, we surveyed a demographic-stratified sample of 10,000 Italian adu...

Background Maternal vaccinations against Influenza, Pertussis, and Covid-19 are recommended in the UK, and vaccines against further infections may become available soon. However, many pregnant women, especially in socially and ethnically diverse areas, have low vaccine uptake. Qualitative studies on the reasons and possible solutions are needed tha...

With more than 4.26 billion social media users worldwide, social media has become a primary source of health information, exchange, and influence. As its use has rapidly expanded, social media has proven to be a "doubled-edged sword," with considerable benefits as well as notable harms. It can be used to encourage preventive behaviors, foster socia...

Introduction We investigated the effect of social media-based interventions on COVID-19 vaccine intention (VI) and confidence in Japan. Methods We conducted a three-arm randomised controlled trial between 5 November 2021 and 9 January 2022 during a low incidence (<1000/day) of COVID-19 in Japan in the midst of the second and the third waves. Japan...

Chatbots have become an increasingly popular tool in the field of health services and communications. Despite chatbots' significance amid the COVID-19 pandemic, few studies have performed a rigorous evaluation of the effectiveness of chatbots in improving vaccine confidence and acceptance. In Thailand, Hong Kong, and Singapore, from February 11th t...

Background: Adolescent girls in China have a low HPV vaccination rate. Although vaccination is recommended by the Chinese health authorities, the cost is not covered by the national immunisation programme. Vaccination delay, among other reasons such as supply shortage and poor affordability, may contribute to low uptake. This sequential mixed metho...

By May 30th, 2022, there were 526,182,662 confirmed COVID-19 cases and 6,286,057 deaths globally; of which Nigeria had recorded 256,028 confirmed cases and 3,143 deaths. By the same time, Nigeria had received a total of 93.9 million doses of the COVID-19 vaccine, enough to vaccinate 25% of the population however, only 27.4 million people (13.3% of...

This qualitative study using in-depth interviews and focus group discussions is the first to investigate HPV vaccination in The Gambia; it provides an in-depth analysis of uptake, knowledge, and perceptions of HPV vaccination as well as trust in Ministry of Health vaccination advice. Despite high uptake rates, knowledge of HPV vaccination was low,...

Background Influenza vaccination is the key to prevent influenza-related disease, especially among high-risk populations. However, influenza vaccine uptake in China is low. This secondary analysis of a quasi-experimental trial aimed to understand factors associated with influenza vaccine uptake among children and older people stratified by funding...

Background: Vaccine hesitancy was defined by the World Health Organization (WHO) in 2019 as a major threat to global health. In Italy, reluctance to receive vaccines is a widespread phenomenon that was amplified during the COVID-19 pandemic by fear and mistrust in government. This study aims to depict different profiles and characteristics of peop...

The COVID-19 pandemic has disproportionately impacted immunocompromised patients. This diverse group is at increased risk for impaired vaccine responses, progression to severe disease, prolonged hospitalizations and deaths. At particular risk are people with deficiencies in lymphocyte number or function such as transplant recipients and those with...

Background Maternal vaccinations against Influenza, Pertussis, and Covid-19 are recommended in the UK, and vaccines against further infections may become available soon. However, many pregnant women, especially in socially and ethnically diverse areas, have low vaccine uptake. Qualitative studies on the reasons and possible solutions are needed tha...

Background: The 2014-2016 Ebola epidemic was largely restricted to the three nations of Guinea, Liberia and Sierra Leone, yet it tested the world's ability to address a potential global pandemic. This study provides an in-depth examination of the role of emotions in the response to the outbreak and engagement with public health measures, and the c...

Background: Vaccine hesitancy has seriously compromised the COVID-19 vaccine roll-out across the Western Pacific; nevertheless, evidence-based recommendations that account for the heterogeneity of vaccine-hesitant populations in this region remain lacking. To help design customized vaccine communication strategies, we sought to investigate the prof...

Dialogue with people who are vaccine hesitant has been recommended as a method to increase vaccination uptake. The process of cultivating dialogue is shaped by the context in which it occurs, yet the development of interventions addressing vaccine hesitancy with dialogue often overlooks the role of context and favors relatively fixed solutions. Thi...

Background The success of vaccination programs often depends on the effectiveness of the vaccine messages, particularly during emergencies such as the COVID-19 pandemic. The current suboptimal uptake of COVID-19 vaccines across many parts of the world highlights the tremendous challenges in overcoming vaccine hesitancy and refusal even in the conte...

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) continued to mutate and spread in 2022 despite the introduction of safe, effective vaccines and medications. Vaccine hesitancy remains substantial, fueled in part by misinformation. Our third study of Coronavirus Disease 2019 (COVID-19) vaccine hesitancy among 23,000 respondents in 23 cou...

Current WHO/UNICEF estimates of routine childhood immunization coverage reveal the largest sustained decline in uptake in three decades with pronounced setbacks across Africa. Although the COVID-19 pandemic has induced significant supply and delivery disruptions, the impact of the pandemic on vaccine confidence is less understood. We here examine t...

Background: Despite the public acceptance of COVID-19 vaccines being necessary to achieve ample immunization rates and, in turn, put an end to the global pandemic, vaccine hesitancy and refusal are on the rise. To detect and address the concerns of those who are hesitant, it is critical to identify all potential factors behind vaccine decision-mak...

Despite the public acceptance of COVID-19 vaccines being necessary to achieve ample immunization rates and, in turn, put an end to the global pandemic, vaccine hesitancy and refusal are on the rise. To detect and address the concerns of those who are hesitant, it is critical to identify all potential factors behind vaccine decision-making in order...

Background Human immunodeficiency virus and acquired immune deficiency syndrome (HIV/AIDS) is still among the leading causes of disease burden and mortality in sub-Saharan Africa (SSA), and the world is not on track to meet targets set for ending the epidemic by the Joint United Nations Programme on HIV/AIDS (UNAIDS) and the United Nations Sustaina...

Background Little is known about how social media platforms can be used to increase COVID-19 vaccine intent. We aimed to investigate the effect of social media-based interventions on vaccine hesitancy in Japan. Methods We conducted a three-arm randomized controlled trial between 5 November 2021 and 9 January 2022. Japanese aged 20 or above who had...

The uptake of non-EPI vaccines, such as influenza and pneumonia vaccines, are very low in China compared to other countries. In China, immunization services are provided by dedicated vaccination service providers (VSPs), and their recommendation is the key to improve vaccine uptake. This study explores VSP recommendation practices for non-EPI vacci...

Digital approaches are increasingly common in clinical trial recruitment, retention, analysis, and dissemination. Community engagement processes have contributed to the successful implementation of clinical trials and are crucial in enhancing equity in trials. However, few studies focus on how digital approaches can be implemented to enhance commun...

Young children aged 6–59 months are recommended as one of the priority groups for seasonal influenza vaccination in China. This study assessed influenza vaccination coverage and the factors associated with vaccination uptake among children in three Chinese provinces. In September 2021, 2081 caregivers with children <5 years completed self-administe...

Background: COVID-19 vaccination has faced a range of challenges from supply-side barriers such as insufficient vaccine supply and negative information environment and demand-side barriers centring on public acceptance and confidence in vaccines. This study assessed global spatiotemporal trends in demand- and supply-side barriers to vaccine uptake...

Background Multiple COVID-19 vaccines have now been licensed for human use, with other candidate vaccines in different stages of development. Effective and safe vaccines against COVID-19 have been essential in achieving global reductions in severe disease caused by severe acute respiratory coronavirus 2 (SARS-CoV-2), but multiple factors, including...

When the term ‘vaccine hesitancy’ first appeared, it was deemed ambiguous and difficult to measure. A systematic review of published articles on vaccine hesitancy suggests it should be defined as a state of indecisiveness regarding a vaccination decision, independently of behaviour, and that it needs new modes of analysis and measurement.

During the COVID-19 pandemic, the emergence of the infodemic and vaccine hesitancy posed a significant challenge to adequate vaccine uptake. In response, conversational AI services such as chatbots have become an increasingly popular tool in the field of health service delivery and communication to increase individuals’ health literacy and vaccinat...

Background Polarized debates about Covid-19 vaccination and vaccine mandates for healthcare workers (HCWs) challenge Belgian HCWs ability to discuss Covid-19 vaccine sentiments with peers and patients. Although studies have identified drivers of HCWs vaccine hesitancy, they do not include effects of workplace interactions and have not addressed con...

BACKGROUND During the early 2020s use of conversational AI (chatbots) in healthcare expanded significantly, especially in the context of increased burdens on health systems and restrictions on in-person consultations with healthcare providers during the COVID-19 pandemic. One emerging use case for conversational AI is related to communicating infor...

Background Since the mid-2010s, use of conversational artificial intelligence (AI; chatbots) in health care has expanded significantly, especially in the context of increased burdens on health systems and restrictions on in-person consultations with health care providers during the COVID-19 pandemic. One emerging use for conversational AI is to cap...

Background Health care professionals are widely considered to be the most trusted source of information on vaccine-related topics. However, several are reporting their own hesitancy around certain vaccines, influencing their intention to vaccinate themselves as well as influencing their recommendations to their patients and target population. Meth...

With approval of more COVID-19 vaccines for children, vaccine attributes may influence parental acceptance and choices. We aimed to assess effects of vaccine attributes and information on herd immunity on childhood COVID-19 vaccine acceptance. A survey experiment was conducted with caregivers of children aged 6 months to 11 years old and health car...

Background China has low seasonal influenza vaccination rates among priority populations. In this study, we aimed to evaluate a pay-it-forward strategy to increase influenza vaccine uptake in rural, suburban, and urban settings in China. Methods We performed a quasi-experimental pragmatic trial to examine the effectiveness of a pay-it-forward inte...