Response to Rotavirus Vaccine in Infants in Ho Chi Minh City in Vietnam

Inclusion Criteria: * Infants (both males and females) between 8 and 9 weeks (i.e. approximately 2 months) of age who are attending Hung Vuong Hospital to receive their standard EPI vaccinations. * Currently registered residents of Districts 5 (where Hung Vuong Hospital is located) or 1, 6, 8, 10, or 11 (districts that are neighbouring district 5) in Ho Chi Minh city, with no specific intention of relocating in the next 12 months. * Informed consent to be enrolled in the study and comply with study procedures, including host genetic studies. Exclusion Criteria: * Refusal of consent. * Parent/ guardian under the age of 18. * Premature (i.e. gestation period \<37 weeks). * Infants who have already been immunized with either a rotavirus vaccine or the standard 2-month EPI vaccinations. * History of hypersensitivity to any components of the vaccine or adverse vaccine event. * History of intussusception or congenital malformation of the gastrointestinal tract in the child that is likely to predispose child to intussusception. * History of severe combined immunodeficiency disease (SCID), acquired immune deficiency syndrome (AIDS) or Human immunodeficiency virus (HIV) positivity, or other known immunodeficiency syndromes that may place the child at risk during immunisation.