HBV vaccine has been recommended as a routine infant vaccination worldwide since 1991 and as a routine adolescent vaccination since 1995. Although there are no federal laws requiring the vaccine for day-care and school attendance, the World Health Organization (WHO) recommends that all countries with routine hepatitis B vaccination programs continue that practice, while countries not currently immunizing against HBV infection adopt such programs immediately. The vaccine is delivered in a series of three intramuscular injections over a six-month period. It requires refrigeration, and injections must be administered by a medical professional, with the total cost ranging between $100 and $150 per person. These factors, coupled with transportation and distribution issues, make mass immunization, especially in Third World countries, next to impossible. In 1996, the Rockefeller Foundation provided a three-year grant for oral vaccine research to the Boyce Thompson Institute for Plant Research Inc. (BTI), a private, not-for-profit organization affiliated with Cornell University. The preclinical trials were funded by the National Institute of Allergy and Infectious Diseases, a division of the National Institutes of Health. Clinical trials in 1999 were funded by Axis Genetics of Cambridge, England. These studies not only paved the way for the development of an edible HBV vaccine, but also supported collaborations with researchers in Mexico for a vaccine that would inoculate children against intestinal diseases such as diarrhea and cholera, which result in high rates of infant mortality in Mexico.