**CDC-9 Inactivated Rotavirus Vaccine (IRV) Microneedle Patch (MNP) Study** This study is testing a new rotavirus vaccine called CDC-9 IRV, which uses a small patch with tiny needles (microneedle patch) to deliver the vaccine into the skin. Rotavirus can cause severe diarrhea and is a serious health issue, especially in developing countries. The goal is to check if this vaccine is safe and how well it boosts the immune system in healthy adults aged 18-45. Participants will get three doses of the vaccine or a placebo over a few months. **Key Points:** - The study involves three doses, with check-ups over a 6-month period. - Participants will be monitored closely for any side effects. - Eligibility includes being healthy, aged 18-45, and meeting certain health criteria. The study is designed to see if this new vaccine approach can work better in places where the current vaccines don't work as well. Participants will help scientists learn more about how to protect people from rotavirus.