Vaccine associated paralytic poliomyelitis.

Area of Science:

• Public Health
• Vaccinology
• Epidemiology

Background:

• Vaccine Associated Paralytic Poliomyelitis (VAPP) is a known risk of Oral Polio Vaccine (OPV).
• OPV use has increased in India's national immunization programs, yet VAPP has received inadequate attention.
• Previous analyses suggested lower VAPP incidence in India, but re-analysis indicates a higher rate.

Purpose of the Study:

• To re-evaluate the incidence of VAPP in India.
• To investigate the discrepancy between recorded OPV doses and isolated vaccine virus in AFP cases.
• To propose a strategy for introducing Inactivated Polio Vaccine (IPV) into India's national program.

Main Methods:

• Re-analysis of data from the National Polio Surveillance Project (NPSP).
• Epidemiological assessment of VAPP incidence based on OPV dose administration.
• Review of trends in Acute Flaccid Paralysis (AFP) cases with vaccine virus isolation.

Main Results:

• Re-analysis suggests VAPP incidence in India is approximately 1 in 1.5-2.0 million OPV doses, higher than reported elsewhere.
• Despite increased OPV administration, the number of AFP cases with isolated vaccine virus has decreased since 1999.
• This contradictory trend may indicate under-administration of OPV or reduced vaccine potency.

Conclusions:

• VAPP may represent a more significant public health issue in India than previously recognized.
• A gradual transition from OPV to IPV in the national program is recommended to eliminate VAPP.
• Introducing IPV can also address other concerns following polio eradication efforts.