The Case for Assessing the Drivers of Measles Vaccine Uptake

"Without accurately measuring the behavioural and social drivers for measles vaccination, and ideally measuring them serially over time, countries cannot design, target and implement interventions that effectively increase and sustain measles vaccine coverage."

According to the World Health Organization (WHO), the behavioural and social drivers (BeSD) of vaccination include four categories: what people think and feel about vaccines, social processes, motivation to vaccinate, and practical barriers to vaccination. However, the drivers of measles vaccine uptake are not necessarily the same as those for other childhood vaccines, and it is unclear how these drivers specifically have changed in light of the COVID-19 pandemic. This paper outlines what is and is not known about the BeSD of measles vaccination and provides recommendations for improving their post-pandemic assessment.

As detailed here, from 2021 to 2022, the estimated number of measles cases worldwide increased by 18%, and the first months of 2024 demonstrated the perpetuation of this worrisome trend. Very high coverage - over 95% of the population - is required to prevent outbreaks, but global first dose measles-containing vaccine (MCV) coverage declined from 86% pre-pandemic to 81% in 2021, the lowest coverage since 2008. The reasons for this decline are multifactorial. Data show that vaccine confidence and trust were impacted by the pandemic.

The BeSD framework is accompanied by both qualitative and quantitative data collection instruments and comprehensive supporting guidance for measuring these drivers. This feature is a benefit because, according to the authors, without accurate measurement (ideally over time), it is easy to assume that the main barriers to vaccination are hesitancy or misinformation, when the actual issue may be access, availability, or a complex mix of multiple factors. The paper outlines what is and is not known about the BeSD of measles vaccination:

• The way people think and feel about measles vaccination continues to be influenced by the discredited 1998 Lancet study reporting fraudulent data linking the measles, mumps, and rubella (MMR) vaccine to autism. Vaccine safety concerns are a significant factor in parents' decision-making about measles vaccines.
• Measles vaccine decision-making is influenced by external social processes. For example, the origins of the modern anti-vaccine movement can be largely traced to the media coverage of the MMR controversy of the 1990s. The MMR vaccine itself has been singled out by anti-vaccine activists and influencers, whose goal is to shape social norms. Religious leaders have also exerted significant influence on measles vaccination. "Understanding the specific social processes that affect measles vaccination decisions is critical, as these may differ between vaccines."
• The practical issues affecting vaccine uptake are multifactorial and can be unique in relation to measles vaccination. For example, the vaccine is heat-sensitive, requiring meticulous cold chain management and reconstitution that complicates storage and delivery and increases the risk of secondary vaccine failure.

For these reasons, the authors suggest that "it is conceivable that measles vaccination has been differentially impacted by the pandemic in many unique and important ways. However, despite the urgent global concern about measles resurgence and inadequate measles vaccine coverage, there is a gap in our understanding of how the social and behavioural drivers of measles vaccination have changed during and since the COVID-19 pandemic....We need serial data on drivers of measles vaccination - and granular data on MCV uptake - if we are to design, target and implement interventions that effectively increase and sustain measles vaccine coverage."

However, validated tools focused on social or behavioural factors associated with measles vaccine uptake are very limited. The WHO Tailoring Immunization Programmes approach employs the COM-B behaviour change wheel to qualitatively assess barriers to uptake, including practical issues, "but this approach is complex, resource intensive, and can be difficult to deploy rapidly and repeatedly. The WHO BeSD tools address both access and acceptance issues and have been designed for use globally, particularly in low- and middle-income countries, but they are not customised for individual vaccines."

Based on their analysis, the authors recommend:

• At a macro level, health departments should invest in and encourage a learning health systems approach to systematically collect data and apply it to inform evidence-based care and decision-making. Some academic institutions offer online short courses and fellowship programmes for low- and middle-income country leaders.
• Countries should establish serial surveillance of the BeSD of measles vaccine uptake (e.g., vaccine confidence, concerns, and social influences) over time. Short-form instruments, such as the BeSD key indicators, may be suitable for embedding in existing population surveys. Partnerships with academic institutions should be considered for local validation of measurement instruments.
• Interventions should be evidence-based and targeted to address specific barriers identified through surveillance. A 2023 systematic review and meta-analysis maps behavioural interventions against the BeSD domains, identifying provider recommendations (social processes domain) and on-site vaccination (practical issues domain) as the most effective strategies to improve uptake.
• Interventions should be locally tailored through community co-design. Community-led and -owned approaches to encourage and sustain vaccine demand are critical, such as building the capacity of health workers, community leaders, and faith leaders to advocate for vaccination. These groups are often highly trusted and influential but might benefit from specific vaccine education and vaccine communication skills training.
• Assessing perceived vaccine accessibility, affordability, and availability is critical, even in settings where vaccinations are provided free of charge. Governments should prioritise guaranteeing availability and optimal supply of vaccines. Officials should employ evidence-based risk communication and response approaches to address vaccine safety signals while maintaining public trust.