Costs were not discounted and quantities and costs were not analysed separately. Cost items were reported separately. The costs of the intervention covered the screening costs (ELISA, Western blot), work-up costs (blood cell count, liver function costs, helper/inducer T-lymphocyte), and treatment costs (zidovudine oral or intravenous, and neonatal therapy), and were compared with an averaged cost for care and follow-up of a random sample of 5 infants infected through vertical transmission. The sources of the cost data were different local or regional organizations. The cost boundary adopted was that of the health care system. The date of the price data was not explicitly specified.