In December 2000, the White House issued an executive memorandum authorizing the WIC program to begin screening clients for childhood immunization status. The motivation for this was the fact that WIC had the access to the greatest number of low-income children and thus had the greatest potential for helping immunization rates. They also directed that immunization screening and referral become a standard part of WIC certification. It mentioned that the new WIC minimum immunization screening and referral is only for use in the WIC program. Across WIC programs, it has become standardized as an accurate, efficient and appropriate screening and referral process. WIC state and local agencies must coordinate with the providers of immunization screening.