Needle-Free Transdermal Patch for Influenza Vaccination

Transdermal vaccination offers a promising alternative to conventional injections by eliminating needle-related risks and improving patient satisfaction. However, because the stratum corneum poses a considerable barrier to antigen delivery, innovative approaches for effective transdermal immunization are necessary. We propose the transdermal influenza vaccine by using a solid-in-oil (S/O) dispersion-based patch formulation for the transdermal delivery of hemagglutinin antigen and CpG oligonucleotide adjuvant. The formulation was prepared by incorporating a S/O dispersion into an adhesive matrix to enhance antigen skin permeation. In vitro and in vivo skin permeation studies demonstrated that the S/O patch achieved 2.5-fold greater antigen delivery compared with a S/O dispersion. Immunization studies in mice revealed that the S/O patch induced robust IgG antibody titers that were comparable to subcutaneous injection, highlighting the potential of the patch as a viable transdermal vaccine platform. Furthermore, histological analysis indicated there was minimal skin irritation, with transient effects resolving within 72 h. These findings suggest that the S/O patch formulation can enable efficient, noninvasive transdermal immunization, offering a practical alternative to injection-based influenza vaccines.