Correlation between Non-Polio Acute Flaccid Paralysis Rates with Pulse Polio Frequency in India.

Area of Science:

• Public Health
• Epidemiology
• Vaccinology

Background:

• India reported its last polio case in 2011, yet non-polio acute flaccid paralysis (NPAFP) rates remained elevated.
• Previous research indicated a correlation between NPAFP rates and oral polio vaccine (OPV) pulse rounds, but causality was not established.
• Following polio eradication efforts, the number of OPV rounds was reduced.

Purpose of the Study:

• To investigate whether the reduction in OPV pulse polio rounds in India led to a decline in NPAFP incidence.
• To analyze the correlation between NPAFP rates and the number of OPV rounds administered, considering cumulative effects.

Main Methods:

• Utilized polio surveillance data from India spanning 2000–2017.
• Examined the correlation between the NPAFP rate and the number of pulse polio rounds conducted annually.
• Assessed the cumulative impact of OPV doses administered over previous years on NPAFP rates, particularly in high-incidence states.

Main Results:

• A significant correlation was found between NPAFP rates and OPV pulse polio rounds (R = 0.46, p < 0.001).
• NPAFP rates began to decrease in 2012, coinciding with the reduction in pulse polio rounds.
• In high-NPAFP states like Uttar Pradesh and Bihar, the strongest correlation (R = 0.76, p < 0.001) was observed when considering cumulative OPV doses over five years.

Conclusions:

• The observed decline in NPAFP following the reduction in OPV rounds suggests a causal link between OPV administration and NPAFP incidence.
• The findings support the hypothesis that OPV administration contributes to elevated NPAFP rates.
• Further reduction in pulse polio rounds may help decrease NPAFP rates in India, now polio-free for over six years.