This study looks at how well new mRNA COVID-19 vaccines work in adults. mRNA vaccines teach our bodies to fight the COVID-19 virus. This study focuses on variants, which are different versions of the COVID virus. If you have already received an mRNA COVID-19 vaccine, you may be eligible. Women who can have children must have a negative pregnancy test and use birth control.
**Exclusion criteria:** If you've had COVID-19 or a fever recently, or if you have certain health problems, you might not join. Also, if you've had a bad reaction to a vaccine before, or have received certain vaccines or treatments recently, you may not participate.
- The study will observe participants for a certain period to see how they respond to the vaccine.
- Participants must attend several visits for tests and check-ups.
- Potential risks include having a reaction to the vaccine.
It's important to follow all the instructions and attend all visits if you decide to participate. This study helps us learn more about protecting people from COVID-19 with new vaccines.