<s>[INST] A new vaccine is being developed against a virus that causes severe gastrointestinal symptoms in children. The vaccine will be tested in a phase 3 trial to determine if it is safe and effective. The researchers want to test the vaccine in children with no prior history of the virus to ensure the most accurate results. The trial will be double-blinded, meaning that neither the researchers nor the children's guardians will know which participants received the placebo or the vaccine.

What type of population is most suitable for this study?[/INST]