These criteria include a minimum CD4 count of 400 cells/mm3, with minimum CD8 count 200 cells/mm3, naïve/memory immunophenotyping suggesting a predominance of naïve T lymphocytes at some previous time point, and protection against tetanus as evidenced by a protective level obtained at least 3 weeks after the 3rd dose of the DTaP vaccine. This evidence concerns the gene CD4 and tetanus.