**Study Summary:** This research is testing a new vaccine, **TI-0010**, for COVID-19 in healthy adults. The study will check the safety, tolerance, and how well the body reacts to the vaccine. Participants will be healthy individuals aged **18-59**. The vaccine uses a special method called "lipid nanoparticles" to deliver the vaccine into the body. Up to **100 people** will join this study and will be placed in groups (called cohorts) to receive different doses. Some will get the vaccine, and others will receive a placebo, which is a harmless substance used for comparison. Key Points: - **Timeline**: Participants will visit the study site several times over a year. - **Doses**: Some will get one dose; others will get two doses. - **Safety**: The study aims to see if there are any side effects within 28 days and over the year. Participants must be in good health, not have had a recent COVID-19 vaccine, and follow certain rules, like using contraception. They should not have severe allergies or serious health problems.