This study is testing a new rotavirus vaccine, called ROTAVAC 5D. Rotavirus is a virus that can cause diarrhea, especially in babies. The study will involve 5,800 healthy babies in Chile, who are 6-8 weeks old. Half will receive the vaccine, and the other half will receive a placebo (a fake vaccine) to compare results. The study is "double-blind," meaning neither the doctors nor the parents will know who is getting the real vaccine.

Some babies will have blood samples taken to check if their bodies create antibodies (proteins that fight germs) after getting the vaccine. Stool (poop) samples will also be collected if the baby gets a tummy illness.

• The study lasts for about a year, with several visits to check the baby's health.
• There might be some risks, like reactions to the vaccine or blood sampling discomfort.
• Parents must not plan to move away within the next year to stay in the study.

Parents need to give permission for their baby to join. Babies who have had certain illnesses or treatments can't join. This research helps find out if the vaccine is safe and works well.