Secondly, while the antimicrobial actions of vitamin D do not outweigh those of intensive-phase therapy, vitamin D does have the potential to act as preventative therapy in both TB contacts, who are not immunosuppressed but live in high burden settings, or in HIV-1 infected individuals with CD4 counts above the threshold for ARV initiation, and in those who are drug-resistant TB contacts for which isoniazid preventive therapy (IPT) is not efficacious. Here, CD4 is linked to tuberculosis.