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Everyone, Everywhere, All at Once: Strengthening Demand Chains for Equitable Vaccination

The world hit two global vaccination milestones in Q2 of 2024. At the end of April, during World Vaccine Week, the World Health Organization celebrated the 50th anniversary of its Expanded Programme on Immunization. In June, the Global Alliance for Vaccines and Immunizations entered its 25th year with a new Gavi 6.0 strategy, setting its course for the next five years. Looking backward, both of these milestones reflect major achievements in preventing disability and death from vaccine-preventable diseases. Looking forward, these temporal landmarks provide opportunities for “fresh starts,” or new commitments to achieving our goals.

The work of the Mercury Project suggests three commitments we can make on the occasion of these global vaccination milestones to ensure that everyone, everywhere benefits from vaccines:

  1. Prioritize vaccine “demand chains” to ensure that vaccines become vaccinations.
  2. Produce and use rigorous social and behavioral science to build vaccine demand chains.
  3. Scale–and keep testing–promising vaccine demand solutions.

1. Prioritize vaccine “demand chains” to ensure that vaccines become vaccinations

Vaccination is an action with clear health benefits—but individuals may face a variety of barriers to realizing those benefits. Vaccinations provide significant returns on investment: $54 USD for every $1 USD spent. But these returns aren’t guaranteed just because vaccines are discovered and distributed. It cannot be taken for granted that because a vaccine exists, vaccinations will occur automatically.

To achieve widespread, equitable vaccination, we must prioritize vaccine “demand chains,” ensuring that people are ready, willing, and able to vaccinate. It goes without saying—almost—that the global community needs a robust pipeline of new vaccines, strong manufacturing in every region of the world, and sturdy supply chains to ensure equitable vaccine supply across countries. Each of these is slated to receive significant, welcome investment in the coming years. 

Having vaccines in-country, however, is not enough to realize their benefits: vaccines must be in clinics, in communities, and, ultimately, in arms. Fully realizing the benefits from vaccines requires overcoming the barriers to vaccination posed by information search costs, decision costs, and logistical costs. People must have access to accurate information about vaccines and vaccine-preventable diseases and must be equipped to navigate potentially contradictory and inaccurate vaccine information. They must also be supported in the act of securing a vaccination. Otherwise, vaccines will remain in inventory systems, not in immune systems. We need to build not only vaccine supply chains, but also vaccine demand chains.

2. Produce and use rigorous social and behavioral science to build vaccine demand chains

Building strong vaccine demand chains—and the primary healthcare systems that support them—requires us to produce and use solutions-oriented social and behavioral science. Through the Mercury Project, the Social Science Research Council and its funding partners are making a significant contribution to the rigorous evidence base about interventions that build vaccine demand and information environments supportive of science-based decision-making. This evidence can guide investment toward scaling proven solutions rather than reinventing the wheel. 

For example, interventions that reduce the costs to individuals of accessing accurate vaccine information and navigating inaccurate vaccine information may be critical to increasing vaccination rates. Mercury Project teams are testing a portfolio of interventions that may reduce individuals’ vaccine information search costs and vaccination decision costs: 

  • In Ghana, the Doctors’ talks team is testing whether training health workers in effective interpersonal communication skills increases vaccination rates.
  • In Côte d’Ivoire, Malawi, Senegal, and Zimbabwe, the Health ambassadors team is testing whether training community nurses and recent STEM graduates in constructive dialogue skills increases vaccination rates.
  • In Haiti, Malawi, and Rwanda, the Community education to build trust team is testing whether a tool that helps community health workers respond to local inaccurate vaccine information increases vaccination rates.
  • In Brazil and Mexico, the Community-crafted messages team is testing whether using community input to craft vaccine messaging on Facebook increases vaccination intentions. 

In addition, reducing the logistical costs of acting on positive vaccine intentions, from making and remembering appointments to securing transportation and time off work, may be another important strategy to increase vaccination rates.

  • In the US, the Boosting boosters at scale team is testing whether ownership language delivered via SMS by a pharmacy chain—“your vaccine is waiting for you”—increases vaccine uptake. 
  • In Sierra Leone, the Marklate don cam team, building on successful prior results, is testing whether bringing multiple vaccines to remote rural communities through mobile vaccine units increases vaccination rates.

Countries seeking to build their vaccine demand chains can use the rigorous evidence about these interventions to choose which programs to stop, which to stop, and which to scale. 

3. Scale—and keep testing—promising vaccine demand solutions

In 2021, when the Mercury Project launched, the rigorous evidence base was insufficient to guide demand-side investments. At that time, vaccine demand evidence was largely derived from one-off studies, with conflicting results across contexts. 

Now, due to investments in the Mercury Project and other initiatives, we have a stronger evidence base. It is time to start building upward from this foundation, seeing how the bricks fit together and support one another rather than fashioning new bricks. We can take what we have learned to put together a common vaccine demand  playbook that countries and communities can use to determine which vaccine demand interventions  to stop, which to start, and which to scale.

While we now know enough to build an evidence-based vaccine demand playbook, it is essential that we keep testing even as we implement the playbook at scale. Behavioral interventions are susceptible to contextual effects. A central tension in scaling behavioral evidence is tempering scaling with continual learning about how broadly interventions generalize across contexts. 

A “master protocol” approach would allow for both scaling and continually testing promising vaccine demand interventions across diverse contexts to generate both locally useful and globally informative findings. Master protocols offer a promising approach to learning-and-doing at scale. In a master protocol, the most cost-effective interventions from the current evidence base would be simultaneously deployed across multiple contexts in a large-scale coordinated randomized controlled trial, significantly advancing our global understanding of which interventions generalize and which do not.

Vaccinations for everyone, everywhere

The achievement of temporal landmarks by the WHO and Gavi this spring provides an opportune moment to make important new commitments to global vaccination goals. By learning from and acting on high-quality social and behavioral science evidence, we can strengthen global vaccine demand chains, ensuring that vaccines on shelves become vaccinations in arms for everyone, everywhere.