Quantification of TRECs (T-cell receptor excision circles) in DNA extracted from Guthrie samples is a sensitive screening test for Specific and SCID. TRECs are small-circle DNA molecules which are by-products of T cell maturation in the thymus, and their numbers reflect the number of recently emigrated T-cells from the thymus. Since all infants with SCID have a profound decrease in T-lymphocytes no matter what gene mutations are involved, logically the number of TRECs present in blood collected via dried blood spots 1-2 days post delivery on SCID babies should be very low when compared with healthy newborns. The TREC assay includes DNA extraction from a 3 mm punch of dried blood specimen in a 96-well plate format. The extracted DNA undergoes Real-time qPCR procedure on 7900 HT Fast Real-time PCR System (ABI). The TREC copy number is calculated relative to a standard curve generated from serially diluted plasmids which contain a known number of TREC. The investigators propose in this study to perform a neonatal screening of SCID, in a population of 200,000 babies over a period of three years. The investigators propose to study the incidence of SCID, mortality & rate of disability, clinical utility and SCID screening to demonstrate that could result in a broad benefit to individuals detected, making screening relatively efforts in spite of the low incidence of the disease.