The researchers say the findings are important for designing, optimising, and implementing targeted interventions to increase vaccine uptake, as they highlight the most effective components across different populations and contexts.
The global decline in vaccine uptake, alongside a rise in preventable disease outbreaks, highlights the urgent need to pinpoint and close gaps in vaccine coverage. Yet no existing reviews assess the effectiveness of individual intervention components across different populations and contexts.
To address this, researchers conducted a component-level analysis of 237 randomised controlled trials in high and upper middle income countries. Their aim was to compare the effectiveness of different content and delivery components of vaccine uptake interventions for all vaccines on the UK schedule and across all age groups.
The 237 trials involved 4,361,717 participants (40% male). Of these, 110 trials were at low risk of bias, 96 had some concerns, and 31 were at high risk.
The results showed that for children, offering payments to cover costs (eg, travel costs) and decision aids were beneficial, while extended vaccination opportunities and information about social factors (eg, acting for the benefit of society) might also increase uptake.
For adolescents and young adults, beneficial effects were shown for personal delivery formats (eg, calls, texts, emails), delivery by community members alongside healthcare professionals, and social factors. There was evidence of a negative effect of decision aids and some evidence of a negative effect of human versus non-human interaction.
For adults, human interaction, extended vaccination opportunities, appointment scheduling help, payments to cover costs, and motivational interviewing to encourage uptake were beneficial. Financial incentives and information on vaccine safety and effectiveness showed some evidence of benefit, while non-human interaction showed a negative effect versus no interaction.
In underserved communities who often face social, economic, and geographical barriers to care, extended vaccination opportunities, financial incentives, and providing reminders increased uptake. The effectiveness of certain components may also have been influenced by the COVID-19 pandemic.
Dr Sarah Davies, Senior Research Associate in Evidence Synthesis in the Bristol Medical School: Population Health Sciences (PHS) and lead author, said: “Our research has found that making vaccination easier and more accessible – through extended opportunities, appointment support, and financial help – could boost uptake.
“Approaches that involve human interaction and trusted community members are effective overall, but the best solutions vary across populations, highlighting the need for targeted and cost‑informed interventions.”
Dr Clare French, Senior Research Fellow in the Bristol Medical School: PHS and principal investigator on the project, added: “Our findings show that there is no one‑size‑fits‑all solution to improving vaccine uptake. Interventions need to be designed around the needs of different age groups and communities, with an emphasis on improving access, community involvement, and consideration of costs and cost‑effectiveness.”
This large study, using complex analyses across diverse interventions and vaccines, provides widely generalisable findings, but the researchers acknowledge some limitations, such as limited data for some intervention components and two-thirds of the trials being US-based.
The research team suggest integrating these findings with local level data to guide the implementation of effective intervention combinations, and that consideration of cost and cost-effectiveness data will further inform decision making around which interventions to implement given limited resources.
Paper
‘Effectiveness of interventions to increase vaccine uptake: component network meta-analysis’ by Sarah R Davies, Clare E French et al. in The BMJ