For instance, scaling access to ART for all identified HIV-infected individuals (aged 15 to 49) in early disease stages in South Africa was found to be more cost-effective than following current guidelines, which recommend access only for those with CD4 counts ≤ 350 cells/Μl, while PrEP could be cost-saving when delivered to individuals at increased risk of infection​ [51]. Here, CD4 is linked to infection.