Benefits and challenges of high-density microarray patches for vaccination among older adults: a qualitative study

Objectives: Microarray Patches (MAPs) deliver vaccines to the upper dermis and epidermis, rich in immune cells. This study explored the perceived safety, usability, and acceptability of High-Density Microarray Patches (HD-MAPs) among older adults aged 50+. Methods: This was a single-centre, single-arm, open-label study using excipient-coated HD-MAPs. A trained user administered two HD-MAPs to each participant's dominant arm, and participants self-administered to their non-dominant arm. Semi-structured interviews were conducted on days 0 and 28. Thematic analysis was used to explore participant experiences. Results: Forty-four older adults were recruited. Themes explored the benefits and challenges of HD-MAPs. Benefits included (1) mass distribution and administration, (2) reduced healthcare burden, and (3) convenience, particularly in low-resource settings due to thermostability and potential for self-administration. Participants felt that use of trained users and self-administration could reduce burden on healthcare resources. Challenges highlighted were (1) safety of unsupervised use, (2) proof of vaccination, and (3) user confidence and cost. Concerns about adverse events and correct dosage were raised, though participants felt reassured by the sensation, applicator sound, and mark after application. Conclusion: HD-MAPs may ease healthcare burdens and improve convenience and acceptability among older adults, offering an alternative to needles and syringes, especially for vulnerable populations. Lay summary: This study explored how older adults (aged 50+) perceived the safety, usability, and acceptability of High-Density Microarray Patches (HD-MAPs), a new, needle-free vaccine delivery method. Participants received the HD-MAP from a trained user and also tried self-administering it. Most found HD-MAPs convenient and easy to use, appreciating their potential for home use and application in remote areas without refrigeration. Participants liked the idea of reducing the burden on healthcare systems and found the HD-MAPs less intimidating than needles. However, some concerns were raised, including safety when used unsupervised, confirming successful vaccine delivery, and cost. Participants suggested using telehealth or supervised settings to enhance confidence. Overall, HD-MAPs were considered a promising vaccination alternative, especially during pandemics and in low-resource settings. The technology may help increase vaccination rates in older adults by offering more accessible, less painful options.