1. even in your 20s, there's still risk to be sick in an unpleasant way 2. we've been using vaccines forever. I've been vaccinated maybe 10 times in my life. Why suddenly should I worry. RNA vaccines may be newer, but 100s of millions of people have been vaccinated, and side effects happen usually soon after the injection. You can also use the AZ vaccine which is more conventional. 3. you prevent other people from getting sick. Even though the vaccine doesn't totally prevent spreading the disease, it does to some extent. 4. Consensus about doctors is that ratio benefit/risk is favorable toward the vaccine for all age classes. I trust my family doctor with my health and follow his recommendation.