This clinical trial is focused on studying the prevention of Cytomegalovirus (CMV) infection using a vaccine called mRNA-1647. CMV is a common virus that can cause health problems in some people, especially those with weakened immune systems or pregnant women. The trial aims to evaluate how well the vaccine works, its safety, and how the body responds to it. The vaccine is given as a solution for injection and is designed to help the body build immunity against CMV.

The study involves healthy participants aged 16 to 40 years. Participants will receive the mRNA-1647 vaccine or a placebo through a series of three injections. The trial will monitor participants over a period of time to see if the vaccine can prevent CMV infection and to check for any side effects. The study will also involve the use of Sodium Chloride 0.9%, which is a common solution used in medical settings, as part of the injection process.

The main goal of the study is to demonstrate the effectiveness of the mRNA-1647 vaccine in preventing CMV infection in participants who have not been previously exposed to the virus. The trial will also assess the safety of the vaccine and how well it is tolerated by participants. This research is important for developing new ways to protect people from CMV and improve public health outcomes.