Abstract
Inactivated Polio Vaccine (IPV) and live Oral Polio Vaccine (OPV) are among the most successful and widely used vaccines in the history of medicine. The history of their development and subsequent evolution in response to changing epidemiological and socio-economic circumstances will be reviewed along with new efforts to develop a new generation of polio vaccines. OPV was responsible for virtual elimination of the disease, and its worldwide eradication may be achieved in few years. Paradoxically, this monumental accomplishment demands introduction of a new generation of vaccines specifically designed for the new polio-free world to ensure the lasting success of the eradication campaign. Both current vaccines have their strengths and weaknesses: OPV is inexpensive and easy to administer, but its virus can revert to virulence and cause paralytic disease. IPV is highly efficient and safe but is more expensive, requires several intramuscular injections, and does not induce fully adequate mucosal immunity. New vaccines must combine the best characteristics of both. Lower cost of IPV and broader immune response could be achieved by using adjuvants, alternative routes of administration, and increasing production yield. Production of IPV is associated with biosecurity concerns because it is made from highly virulent strains. Novel approaches to reduce virulence of strains used for IPV manufacture will be discussed. Development of a more genetically stable OPV is underway by attempting to reduce rates of mutations and recombination. Polio vaccines were a paradigm for many other vaccines, and lessons learned from their evolution could help develop other prophylactic products.