More than 2 billion people worldwide are fully vaccinated against COVID-19. However, many who live in resource-limited countries haven't been able to get vaccines, partly because these areas lack temperature-controlled shipping and storage facilities. Now, researchers reporting in ACS Nano have developed a microneedle patch that delivers a COVID-19 DNA vaccine into the skin, causing strong immune responses in cells and mice. Importantly, the patch can be stored for over 30 days at room temperature.