M. Newell, We are grateful to all women and children enrolled in the study and the continued dedication of field, clinic and data management staff at the Africa Centre, in particular Thembi Blose, Zanele Fakude, Cookie Govender, Nqobile Mkhwanazi, Londiwe Mthethwa, Samukelisiwe Mtshali and Ntombizodumo Mkwanazi. We are also grateful to Jan van den Broeck and Colin Newell who assisted with data management during the study and analyses; Dave Perlman and Kobus Herbst for their assistance in the design of the database; Deven Patel for advice and analytical support Jane Lucas and Felicity Savage King for assistance in the initial formative pilot work and training, particular we wish to thank the Community Liaison Office of the Africa Centre and the Community Advisory Board for their guidance and feedback throughout the study

H. Coovadia, N. Rollins, R. Bland, K. Little, A. Coutsoudis et al., Mother-to-child transmission of HIV-1 infection during exclusive breastfeeding in the first 6 months of life: an intervention cohort study, The Lancet, vol.369, issue.9567, pp.1107-1123, 2007.
DOI : 10.1016/S0140-6736(07)60283-9

M. Chopra and N. Rollins, Infant feeding in the time of HIV: rapid assessment of infant feeding policy and programmes in four African countries scaling up prevention of mother to child transmission programmes, Archives of Disease in Childhood, vol.93, issue.4, pp.288-91, 2007.
DOI : 10.1136/adc.2006.096321

T. Doherty, M. Chopra, D. Jackson, A. Goga, M. Colvin et al., Effectiveness of the WHO/UNICEF guidelines on infant feeding for HIV-positive women: results from a prospective cohort study in South Africa, AIDS, vol.21, issue.13, pp.1791-1798, 2007.
DOI : 10.1097/QAD.0b013e32827b1462

D. Mbori-ngacha, R. Nduati, G. John, M. Reilly, B. Richardson et al., Morbidity and Mortality in Breastfed and Formula-Fed Infants of HIV-1???Infected Women, JAMA, vol.286, issue.19, pp.2413-2433, 2001.
DOI : 10.1001/jama.286.19.2413

I. Thior, S. Lockman, L. Smeaton, R. Shapiro, C. Wester et al., Breastfeeding Plus Infant Zidovudine Prophylaxis for 6 Months vs Formula Feeding Plus Infant Zidovudine for 1 Month to Reduce Mother-to-Child HIV Transmission in Botswana, JAMA, vol.296, issue.7, pp.794-805, 2006.
DOI : 10.1001/jama.296.7.794

C. Kilewo, Prevention of mother-to-child transmission of HIV-1 through breastfeeding by treating mothers prophylactically with triple antiretroviral therapy in Dar es Salaam, Tanzania -the MITRA PLUS study . Cross-track Session: 4th IAS Conference on HIV Pathogenesis, Treatment and Prevention: Abstract no, TUAX101, 2007.

V. Arendt, AMATA study: effectiveness of antiretroviral therapy in breastfeeding mothers to prevent post-natal vertical transmission in Rwanda . Cross-track Session: 4th IAS Conference on HIV Pathogenesis, Treatment and Prevention: Abstract no, TUAX102, 2007.

L. Palombi, M. Marazzi, A. Voetberg, and N. Magid, Treatment acceleration program and the experience of the DREAM program in prevention of mother-to-child transmission of HIV, AIDS, vol.21, issue.Suppl 4, pp.65-71, 2007.
DOI : 10.1097/01.aids.0000279708.09180.f5

B. Tonwe-gold, D. Ekouevi, I. Viho, C. Amani-bosse, S. Toure et al., Antiretroviral Treatment and Prevention of Peripartum and Postnatal HIV Transmission in West Africa: Evaluation of a Two-Tiered Approach, PLoS Medicine, vol.346, issue.8, p.257, 2007.
DOI : 10.1371/journal.pmed.0040257.sd005
URL : https://hal.archives-ouvertes.fr/inserm-00170648

T. Doherty, D. Mccoy, and S. Donohue, Health system constraints to optimal coverage of the prevention of mother-to-child HIV transmission programme in South Africa: lessons from the implementation of the national pilot programme, Afr Health Sci, vol.5, issue.3, pp.213-221, 2005.

D. Jackson, M. Chopra, T. Doherty, M. Colvin, J. Levin et al., Operational effectiveness and 36 week HIV-free survival in the South African programme to prevent mother-to-child transmission of HIV-1, AIDS, vol.21, issue.4, pp.509-525, 2007.
DOI : 10.1097/QAD.0b013e32801424d2

R. Bland, N. Rollins, H. Coovadia, A. Coutsoudis, and M. Newell, Infant feeding counselling for HIV-infected and uninfected women: appropriateness of choice and practice, Bulletin of the World Health Organization, vol.85, issue.4, pp.289-96, 2007.
DOI : 10.2471/BLT.06.032441

S. Cassol, M. Gill, R. Pilon, M. Cormier, R. Voigt et al., Quantification of human immunodeficiency virus type 1 RNA from dried plasma spots collected on filter paper, J Clin Microbiol, vol.35, issue.11, pp.2795-801, 1997.

D. Brambilla, C. Jennings, G. Aldrovandi, J. Bremer, A. Comeau et al., Multicenter Evaluation of Use of Dried Blood and Plasma Spot Specimens in Quantitative Assays for Human Immunodeficiency Virus RNA: Measurement, Precision, and RNA Stability, Journal of Clinical Microbiology, vol.41, issue.5, pp.1888-93, 2003.
DOI : 10.1128/JCM.41.5.1888-1893.2003

E. Kaplan and P. Meier, Nonparametric Estimation from Incomplete Observations, Journal of the American Statistical Association, vol.37, issue.282, pp.457-81, 1958.
DOI : 10.1214/aoms/1177731566

D. Cox and D. Oakes, Analysis of survival data, 1984.