Study design and participants

Detailed methods for this single-blind, parallel-group, open-label, randomised, controlled trial have been published previously.¹⁵ Briefly, infants with no clinically significant maternal or perinatal history and who were born at or after 36 weeks' gestation were recruited at age 2 months by community health staff in districts 4 and 7 in Ho Chi Minh City, Vietnam, and were followed-up until age 24 months. Infants were excluded if they had any known allergy to any component of the vaccine or previously had an allergic or anaphylactic reaction to any vaccine, had a known immunodeficiency disorder, or were born to a mother with HIV. Full details of the participant eligibility criteria and recruitment processes have been described previously.¹⁵

Parents or legal guardians provided written informed consent for each participant. The study was approved by the Human Research Ethics Committee of the Northern Territory Department of Health and Menzies School of Health Research (EC00153) and the Vietnam Ministry of Health Ethics Committee. The protocol was also approved by the Institutional Review Board at the Pasteur Institute of Ho Chi Minh City. The protocol has been published previously.¹⁵