Previously the recommendation was days 0, 3, 7, 14, and 28.
On July 2009 (this is late breaking!!) the Advisory Committee on Immunization Practices (ACIP) recommended a change to a 4-dose regimen instead on days 0, 3, 7 and 14. The committee members made this decision after hearing that a large number of Americans exposed to rabies each year only get 3 or 4 shots and none of them have developed rabies. The shots cost between $100 - $200 each.
Despite this ACIP recommendation, none of the power house references including the CDC, Sanford Guide, or UptoDate have yet to change their recommended 5 dose regimen. Perhaps it's in the works but until then, I'm sticking with 5 shots. Call me a meanie but I think that if you tell patients they only need 4 doses they'll end up getting only 2 or 3.
Source
"ACIP Provisional Recommendations for the Prevention of Human Rabies" http://www.cdc.gov/vaccines/recs/provisional/downloads/rabies-July2009-508.pdf. 10 July 2009.
Herriman, R. "Advisory Committee on Immunization Practices: just 4 rabies shots needed post-exposure" examiner.com. http://www.examiner.com/x-7707-Infectious-Disease-Examiner~y2009m6d28-Advisory-Committee-on-Immunization-Practices--just-4-rabies-shots-needed-postexposure