The controversy over optimal polio immunization may continue as long as poliovirus persists. Strictly on the basis of worldwide health, the best decision would be to continue immunization with oral vaccine until with poliovirus has been eradicated from the planet. Developed countries may wish to use parenteral vaccine exclusively in an effort to prevent vaccine- associated complications, but then the population might not be protected against imported wild poliovirus. Immigrants from endemic areas remain a source of wild poliovirus, and travelers to such areas can acquire asymptomatic infection and serve as potential vectors for transmission after returning home. Development of paralytic poliomyelitis from wild poliovirus as an unintended consequence of attempting to prevent its occurrence after vaccination would be a cruel irony. Thus, in developed countries with good hygienic conditions, use of the sequential parenteral-oral vaccine schedule is advised, because it combines the advantages of both vaccines and reduces the risk of vaccine-associated complications resulting from oral vaccine use alone. However, in developing countries where wild poliovirus still circulates, oral vaccine is preferable because of its convenient administration and low cost. Even in developed countries, exclusive use of oral vaccine may be chosen because of personal, parental, or provider preference, especially if use of injections would decrease compliance. Oral vaccine is recommended for primary immunization in children aged 6 months or older who have not ben vaccinated and in whom an accelerated immunization schedule is necessary. Use of oral vaccine avoids adding to the number of various injections required at each visit. Selected patients at high risk for vaccine-associated adverse effects should be immunized with parenteral vaccine only. Included are immunocompromised patients and their households contacts and unvaccinated or partially vaccinated healthcare workers. Parents of children receiving oral vaccine should consider undergoing parenteral immunization if their poliovirus vaccination record is not complete.
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