Vitamin D supplementation to prevent acute respiratory infections among Indigenous children in the Northern Territory: a randomised controlled trial

Arm 1: Interventional Group Mother: 0.4 ml (~35 IU/µl) of liquid vitamin D supplement orally once per week, total 14000 IU/week (equivalent 2000 IU/day), from 28-34 weeks gestation (inclusive) until delivery. Infant: 0.2 ml (~21 IU/µl) of liquid vitamin D supplement orally once per week, total 4200 IU/week (equivalent 600 IU/day), from birth until 4 months of age Reduced dose for infants discharged from hospital with a routine recommendation to take oral vitamin D 400 IU/day: Infant: 0.14 ml (~21 IU/µl) of liquid vitamin D supplement orally once per week, total of 3000 IU/week (equivalent to 430 IU/day), from birth until 4 months of age. Maximum possible dose received by infant is 5800 IU/week (830 IU/day). Safe tolerable upper limit for neonates is 7000 IU/week. Administration of study medication: Participants will be allocated to weekly supervised administration of study medication. Study staff or midwives, child health nurses and community workers in allocated clinics will be tasked with locating/recalling participants and administering the supervised dose of study medication. Those participants who cannot be located within 3 days of scheduled dose will be considered as having a ‘missed dose’. These participants will move on to the next dose. There will be no catch up dose.