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Why have vaccination programs reduced cases of polio worldwide?

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Infographic showing estimated lives saved by childhood vaccinations worldwide from 1974 to 2024, with syringe-shaped bars for each disease. Measles tops the list at 93.71 million lives saved, followed by tetanus, whooping cough, and others, for a total of 153.84 million lives saved. — vaccine Vaccines and the estimates of lives saved over the period 1974–2024.

Vaccination programs have drastically reduced polio cases worldwide by generating protective antibodies that enable the body to respond effectively to the virus. Two primary vaccines have been instrumental in this success: the inactivated poliovirus vaccine (IPV), which circulates in the bloodstream, and the oral poliovirus vaccine (OPV), which stimulates both systemic and local immune responses.1

Beyond individual protection, these programs leverage the principle of herd immunity, where a large proportion of the population becomes immune, leaving the virus with too few susceptible hosts to sustain its spread. Notably, the OPV can also provide indirect immunization to others through the fecal-oral route as the attenuated virus is shed by the recipient.21

Through global initiatives led by organizations such as the World Health Organization, mass immunization campaigns have successfully limited the disease to only a few endemic regions, marking one of the greatest achievements in modern medicine.342