‘Only twice a year’: a qualitative exploration of 6-month antiretroviral treatment refills in adherence clubs for people living with HIV in Khayelitsha, South Africa by Keene, CM, Zokufa, N, Venables, EC, Wilkinson, L, Hoffman, R, Cassidy, T, Snyman, L, Grimsrud, A, Voget, J, von der Heyden, E, Zide-Ndzungu, S, Bhardwaj, V, Isaakidis, P