Microarray patches (MAPs) offer the possibility of improved vaccine thermostability and dose-sparing potential as well as the potential to be safer, more acceptable, easier to use and more cost-effective for the administration of vaccines than injection by needle and syringe. Here, we report a Phase I trial using the Vaxxas high-density MAP (HD-MAP) to deliver a live-attenuated Measles (Edmonston-Zagreb) and Rubella (RA27/3) vaccine into the upper arm of healthy young adults (18 to 50). The primary objective was to evaluate the safety and tolerability of a single high- and low-dose of Measles and Rubella vaccine by the high-density microarray patch (HD-MAP), compared to an uncoated (placebo) HD-MAP, and subcutaneous (SC) administration of a standard adult human dose of MR-Vac (Serum Institute of India). Secondary objectives were to evaluate the immune response by assessing IgG and neutralisation antibody titres and to assess the HD-MAP skin penetration by scanning electron microscopy (SEM). Vaccination was well tolerated and no serious adverse advents, or severe adverse events related to study treatment were reported. Local reactions at the application site were observed, such as erythema. Immune response was evident in all non-placebo groups at Day 28 and 56 and comparable between HD-MAP and MR-Vac groups, with pre-vaccination titre predictive of the immune response. Live-attenuated MR vaccine on the HD-MAPs demonstrated excellent thermostability at 2-8 °C over 24 months, including controlled temperature excursions of 3 days at 40 °C at the start and end of shelf life. Overall, this trial demonstrated that delivery of live-attenuated MR by a HD-MAP is safe, tolerable and induces an immune response comparable to SC injection in healthy adults1.