Identifying ways to boost vaccine coverage is essential for saving lives. A new study provides an in-depth meta-analysis that explores which vaccination intervention strategies are most effective and whether these strategies vary in effectiveness across different countries.
Vaccines are both safe and effective, significantly reducing the rates of death and illness. However, global vaccination rates remain low and have been declining, increasing the risk of outbreaks from vaccine-preventable diseases such as Covid-19, influenza, measles, polio, and human papillomavirus (HPV).
Discovering strategies to improve vaccine coverage could have a life-saving impact. A recent paper by researchers from the University of Pennsylvania presents the first thorough meta-analysis that assesses which vaccination intervention techniques yield the most significant results and how these methods may perform differently in various countries.
Published in Nature Human Behaviour, the study titled “A systematic review and meta-analysis of strategies to promote vaccination uptake,” evaluates findings from 88 eligible randomized-controlled trials involving 1,628,768 participants across 17 countries. Previous meta-analyses have often focused on specific vaccines, targeted interventions, or particular populations, limiting the ability to compare different strategies or assess their effectiveness across regions.
According to co-author Dolores AlbarracÃn, a professor at the University of Pennsylvania and director of the Communication Science division at the Annenberg Public Policy Center, “Understanding which methods effectively boost immunization rates and the conditions under which they excel could help global public health officials utilize resources more efficiently and ultimately yield better health outcomes.”
The researchers explored seven vaccination intervention strategies: improving access to vaccination, sending reminders, offering incentives (such as monetary rewards), providing information, correcting misinformation, fostering both active and passive motivation, and teaching behavioral skills.
Effective vaccination intervention strategies
The study revealed that interventions could lead to a 50 percent higher likelihood of vaccination compared to “control” scenarios without any intervention. Among the strategies, two stood out as particularly effective for boosting vaccination uptake. While interventions aimed at increasing access to vaccines showed moderate success, especially in regions with limited healthcare access, the impact of providing incentives was minimal, and the other methods did not significantly alter vaccination rates. For instance, initiatives focusing on providing information or correcting misinformation had no measurable effect on vaccination uptake.
Measures to enhance vaccine access included assistance with transportation or delivering vaccines directly to locations such as nursing homes, private residences, and workplaces. These approaches increased the likelihood of vaccination threefold, demonstrating even more pronounced effects in lower-income countries strapped for resources and access to healthcare.
Incentive-based interventions, such as a study in the U.S. that resulted in an 85% influenza vaccination rate when physicians received $1.60 per dose reimbursement compared to a 70% rate at $0.80, showed some effectiveness; however, the overall impact of incentives remained relatively small as suggested by the meta-analysis findings.
“Public health officials frequently assert that ensuring vaccine access is a fundamental step towards promoting vaccination,” AlbarracÃn noted. “Our meta-analysis reinforces this assertion with solid evidence, highlighting its particular importance in underfunded areas with limited healthcare access. Conversely, while misinformation can pose significant democratic challenges, correcting it does not guarantee that people will engage in health-promoting behaviors like vaccination.”
The authors emphasize that there are numerous hurdles to increasing access in underprivileged areas, making it essential to recognize the critical nature of this type of intervention.
The paper “A systematic review and meta-analysis of strategies to promote vaccination uptake” was published on August 1, 2024, in Nature Human Behaviour. In addition to AlbarracÃn, the authors include Sicong Liu, who was a postdoctoral researcher in AlbarracÃn’s Social Action Lab at Penn and is now a professor at South China Normal University; Marta Durantini, clinical research director at APPC; Christopher Calabrese, former postdoctoral fellow at APPC and now an assistant professor at Clemson University; and Flor Sanchez, a professor at Universidad Autónoma de Madrid.
