2. Polio eradication
Bruce Aylward, Arnab Acharya, Sarah England, Mary Agocs, Jennifer Linkins
Polio: disease & control
- Paralytic poliomyelitis:
- spread primarily through fecal-oral route
- enters the spinal column paralysis
- destroys nerve cells resulting in muscle
- Inactivated poliovirus vaccine (IPV) & oral polio vaccine (OPV) eradicated polio in ‘West’, but remained a problem in developing nations
- 1988 World Health Assembly voted to eradicate
The three strains of paralytic poliomyelitis spread primarily through the fecal-oral route, entering the spinal column and destroying nerve cells resulting in paralysis of the muscles. Paralysis is usually permanent. Even among those who recover, one third may experience a recurrence of muscle pain, exacerbation of existing weakness, or new weakness and paralysis, 15-40 years later as ‘post-polio syndrome’. Because the majority of its victims survive the acute illness, 20 million people today live with the consequences of polio.
By 1963 an two effective vaccines were licensed against the disease. The inactivated poliovirus vaccine (IPV) led to the virtual elimination of the disease from industrialized countries, and the oral polio vaccine (OPV) extinguished most of the final chains of transmission in ‘the West’. This OPV, developed from a weakened (attenuated) strain of the virus was of lower cost, simpler administration and heightened gut immunity, facilitating its use and impact in developing countries. By 1974, substantial progress towards smallpox eradication had stimulated efforts to scale up national immunization services in developing countries, such that by 1990 routine childhood immunization coverage against polio had risen from 5% to >70% worldwide.
Despite this significant disparities in immunization coverage, particularly in sub-saharan Africa, remained. In 1988, as the World Health Assembly (WHA) voted to eradicate polio, the causative virus was either proven or believed to be circulating in more than 125 countries on 5 continents (next slide).