Novel Technologies for Intradermal Delivery of Fractional-Dose Inactivated Poliomyelitis Vaccine: Review of Implementation Research and Implications for Equitable Vaccine Access

INTRODUCTION: Recent trends in intradermal (ID) vaccination, as seen in the Global Polio Eradication Initiative and in the 2022 monkeypox (mpox) pandemic, are a reminder that vaccine administration to the dermis is a valuable alternative to the traditional routes of parenteral delivery. Despite favorable policy towards ID fractional inactivated polio vaccine (fIPV) in anticipation of oral polio vaccine (OPV) cessation, and despite WHO’s emergency-use authorization of fractional ID mpox vaccine in response to the 2024 mpox public health emergency of international concern, ID delivery remains an underutilized strategy with the potential for broader impact including improved coverage and cost savings. We aim to provide a comprehensive review of the published implementation research on novel ID delivery methods used for fIPV immunization to better understand the available ID delivery options, their implementation challenges, benefits, and opportunities for broader use for ID delivery of other vaccines including rabies, malaria, and mpox. METHODS: A literature search was conducted using PubMed [https://pubmed.ncbi.nlm.nih.gov/] to identify literature in any language, published between January 2015 to July 2024 with the terms “inactivated polio vaccine” and “intradermal delivery”. We identified studies that included implementation research on novel alternatives to needle and syringe (NS) ID delivery of fIPV. RESULTS: Of the 59 publications identified in the search, 14 met the criteria as original studies on human subjects using novel delivery methods for ID administration of commercial fIPV vaccines. Five novel technologies were identified. In general, novel ID delivery technologies compared favorably against NS delivery. Benefits of individual technologies include high acceptance with both healthcare workers and caregivers, improved coverage rates, and cost savings. Two ID delivery technologies for fIPV are commercially available. The needle-free technology, Tropis-ID® (PharmaJet), has the most extensive body of implementation research among the alternatives reviewed and is the only technology in this review to achieve WHO-prequalification. CONCLUSION: Novel technologies for ID delivery of fIPV are viable, and, in some cases, offer advantages over ID delivery with NS. Commercially available needle-free ID delivery has been thoroughly researched for campaign use and shown to reduce costs and increase coverage for polio immunization programs. ID delivery using novel alternatives to NS can be a valuable strategy for increasing equitable access to vaccines and for addressing vaccine shortages during campaigns and pandemic response. Commercially available needle-free ID delivery can increase campaign reach, enable effective strategies such as house-to-house campaigns, and potentially empower personnel without formal health training to administer vaccines. These results also suggest alternative ID delivery methods should be evaluated in new vaccine development.