Co-trimoxazole as prophylaxis against opportunistic infections in HIV-infected Zambian children (CHAP): a double-blind randomised placebo-controlled trial. by Chintu, C, Bhat, G, Walker, A, Mulenga, V, Sinyinza, F, Lishimpi, K, Farrelly, L, Kaganson, N, Zumla, A, Gillespie, S, Nunn, A, Gibb, D