Lay summary
Bronchiolitis, an often serious lung infection affecting young children, is the leading cause of infant hospitalisation. Admission rates are 3-5 times higher for Maori and Pacific children, the cause of which is not fully understood. This Maori-led project builds on our previous research, pilot and international collaborations, and uses a case-control study and kaupapa-Maori methodology to explore underlying risk factors contributing to the disparities seen for Maori and Pacific children. It will also investigate whether vitamin D deficiency is associated with increased bronchiolitis severity. 1,050 children