Vaccine access remains uneven globally, with cost and supply chain limitations preventing widespread coverage in low- and middle-income countries. Fractional dosing—administering a reduced vaccine dose while maintaining efficacy—could help stretch limited supplies and budgets. However, evidence on which vaccines work with fractional dosing is scattered, leaving policymakers without clear guidance.

What the Project Could Do

One way to address this gap could be a systematic review of fractional vaccine dosing trials. This review might:

• Catalog which vaccines have been tested with reduced doses and their outcomes (efficacy, safety, immune response).
• Identify patterns—such as whether certain vaccine types (e.g., mRNA, live-attenuated) respond better to fractional dosing.
• Highlight promising candidates for future trials or immediate implementation.

The analysis could include published studies, unpublished trial data, and regulatory filings, focusing on high-impact vaccines like measles, HPV, and COVID-19. Where possible, meta-analysis might quantify how dose reductions affect outcomes.

Potential Impact and Stakeholders

Such a review could benefit:

• Global health organizations (e.g., WHO, Gavi), by providing evidence to update vaccine guidelines.
• Low-resource governments, by identifying cost-saving dosing strategies.
• Researchers, by mapping gaps for future studies.

Stakeholder incentives vary. For example, vaccine manufacturers might resist fractional dosing if it lowers revenue per dose, but could benefit from expanded markets if pricing adapts. Regulators would need robust evidence, while advocacy groups might champion the equity benefits.

How It Might Be Executed

A phased approach could start with a 3–6 month scoping phase to define criteria and gather data from sources like PubMed and ClinicalTrials.gov. Next, 6–9 months could be spent synthesizing findings and drafting a public report. Finally, dissemination to policymakers through briefings could help drive adoption. Challenges like inconsistent trial designs or industry reluctance might be addressed by focusing on transparent methodology and engaging regulators early.

By consolidating fragmented evidence, this project could unlock fractional dosing as a tool for fairer vaccine access.