Poliovirus combined immunization with inactivated and live attenuated vaccines

Abstract

Since the introduction of inactivated poliovirus vaccine in 1955 and live oral poliovirus vaccine in 1962, the number of cases of paralytic poliomyelitis has declined dramatically. In the United States, approximately five cases of poliomyelitis are reported annually and all of them are vaccine-associated. World-wide, there are approximately 200000 cases of natural poliomyelitis. Both the inactivated and live vaccines have proven to be highly effective. The disadvantages of inactivated vaccine are relatively poor mucosal immunity and a belief that booster doses are required to maintain immunity. Live oral vaccine, on the other hand, is associated with paralytic poliomyelitis and poor seroconversion rates in underdeveloped regions of the world. A new enhanced potency inactivated vaccine is more immunogenic, induces greater mucosal immunity, and requires less frequent boosting than earlier inactivated preparations. A sequentional immunization schedule consisting of two doses of enhanced potency inactivated vaccine followed by two doses of the live oral vaccine has been shown to induce excellent systemic and local immunity that is long lasting. The introduction of sequentional immunization as the schedule of choice will require additional simplification of a currently complex vaccine program for polio.