The CDC's Center for Infectious Diseases recommendations ranking scheme Category IA means that the recommendations are:

a. strongly recommended for all hospitals, and strongly supported by well- designed experimental or epidemiologic studies.
b. strongly recommended for all hospitals and reviewed as effective by experts and a consensus of HICPAC based on strong rationale and suggestive evidence, although definitive scientific studies have not been done.
c. suggested for implementation in many hospitals. Recommendations may be supported or suggested by clinical or epidemiological studies, a strong theoretical rationale, or definitive studies applicable to some, but not all, hospitals.
d. practices for which insufficient evidence or consensus regarding efficacy exists.

a