The IMpact of Vertical HIV infection on child and Adolescent SKeletal development in Harare, Zimbabwe (IMVASK Study): a protocol for a prospective cohort study oleh Hilda Mujuru, Rashida Ferrand, Suzanne Filteau, Andrea M Rehman, Ruramayi Rukuni, Celia Gregson, Cynthia Kahari, Farirayi Kowo, Grace McHugh, Shungu Munyati