Understanding "Pulse Polio"
The term "Pulse Polio" refers to mass vaccination campaigns where oral poliovirus vaccine (OPV) is administered to large populations in short, intensive "pulses" or rounds to rapidly interrupt wild poliovirus transmission during outbreaks or in endemic areas 1.
Origin and Rationale of the Term
The "pulse" terminology describes the rapid, synchronized delivery of OPV to entire populations (often >80-95%) within a very short timeframe—typically days to weeks—followed by subsequent rounds 1.
This strategy creates a sudden, high-intensity wave of immunity that interrupts viral circulation, hence the term "pulse" reflecting the concentrated, periodic nature of vaccine delivery 1.
OPV is specifically chosen for these campaigns because it induces antibodies in more recipients after a single dose compared to IPV, provides superior intestinal immunity that limits community spread, and creates beneficial secondary spread through vaccine virus shedding 1.
Evidence Supporting Pulse Strategy
During the 1996 Albania outbreak, cases decreased 90% within 2 weeks after a single OPV dose was given to >80% of the population aged 0-50 years, with no additional cases after a second round 1.
In Finland's 1984-85 outbreak, approximately 4.8 million OPV doses were administered to 95% of the population in pulse rounds after initial IPV boosting 1.
Rapidly implemented mass vaccination campaigns with high coverage have been similarly effective in interrupting wild poliovirus outbreaks in multiple countries 1.
Why "Pulse" Rather Than Continuous Vaccination
The pulse approach differs from routine immunization by targeting entire populations simultaneously rather than individual age cohorts over time 1.
As a live attenuated virus, OPV replicates in the intestinal tract and protects more susceptible persons in a population, making it the preferred vaccine for rapid intervention 1.
The strategy capitalizes on OPV's ability to create intestinal immunity that blocks wild poliovirus replication and transmission, effectively stopping epidemic spread 1.
Current Context
The Global Polio Eradication Initiative has used pulse immunization campaigns since 1988, reducing cases by 99.9% 2.
While pulse polio campaigns with OPV remain critical for outbreak control globally 1, the United States switched to an all-IPV schedule in 2000 to eliminate vaccine-associated paralytic polio (VAPP) cases 1, 3.
Wild poliovirus type 1 now persists only in Afghanistan and Pakistan, where pulse campaigns continue 2, 4.