intestinal immunity, is simple to administer, is well accepted by patients, results in some immunization of unvaccinated contacts, and has eliminated disease caused by wild-type poliovirus in the United States. In the past, the CDC's ACIP has also endorsed the use of OPV for routine vaccination.

In the United States, OPV is given at ages 2 and 4 months with DTP and Hib vaccines, at ages 6 to 18 months with hepatitis B vaccine, and at 4 to 6 years with either DTP or diphtheria and tetanus toxoids and acellular pertussis vaccine (DTaP). Adults who are incompletely immunized against polio can receive either OPV or IPV if they are at risk of exposure to the disease, e.g.: travelers to areas where endemic poliomyelitis persists; members of communities or special population groups experiencing disease caused by wild-type poliovirus; laboratory workers handling specimens potentially contaminated with or containing poliovirus; health care workers in contact with patients who may be excreting poliovirus; and child-care workers in contact with vaccinated infants and young children. Parents who are incompletely immunized should receive a supplemental dose of vaccine at the time of or prior to their infant's immunization.

Those in whom OPV is contraindicated include individuals with immunodeficiency disorders (including HIV infection, combined immunodeficiency, abnormalities of immunoglobulin synthesis, leukemia, and lymphoma or other generalized malignancy), patients receiving immunosuppressive therapy, and those with household contacts receiving such therapy. In addition, subsequent siblings of immunodeficient children should not receive OPV, and previously unvaccinated adults generally should not receive OPV. Such contraindications, if observed, should prevent some recipient and contact cases of polio.

Data about the mucosal immunity induced by OPV are available. A U.S. study by Onorato and colleagues (1991) examined children who had been immunized with either IPV or OPV and who were then subsequently challenged with a monovalent type 1 virus used in OPV, to simulate exposure to wild-type poliovirus. After the challenge, virus shedding was higher from IPV-immunized children than from OPV-immunized children. Sutter and Patriarca (1993) looked at similar data. Virus shedding from naturally immune, OPV-vaccinated, IPV-vaccinated, and susceptible control or naive children was assessed. OPV-vaccinated and naturally immune children had similar levels of virus shedding. Virus shedding from children who received IPV was higher but was not nearly as high as shedding from susceptible hosts. The systemic response to the first dose of OPV is primarily to type 2 virus, and most children develop an antibody response to all three types after two doses.