Question
Prophylaxis of poliomyelitis
Answer
Prophylaxis of poliomyelitis (caused by poliovirus, an enterovirus transmitted by the faecal-oral route) relies primarily on active immunization, supported by general sanitation/hygiene measures.
Active immunization:
- Oral Polio Vaccine (OPV) — a live attenuated trivalent (now bivalent, following global eradication of wild poliovirus type 2) vaccine, given orally; induces both systemic (IgG) and local intestinal mucosal (secretory IgA) immunity — the mucosal immunity is particularly important for interrupting faecal-oral transmission and achieving community/herd protection, since vaccinated individuals can also spread the attenuated vaccine strain to unvaccinated contacts, extending population immunity. OPV is the mainstay of global polio eradication campaigns given its ease of oral administration (no needles required) and lower cost, enabling mass vaccination campaigns.
- Inactivated Polio Vaccine (IPV) — a killed vaccine, given by injection, inducing systemic (humoral) immunity without inducing mucosal IgA to the same degree as OPV, and without any risk of vaccine-associated paralytic poliomyelitis (a very rare but recognized complication of OPV, caused by reversion of the attenuated vaccine strain to a more neurovirulent form) — increasingly incorporated into national schedules (either alone or in combination with OPV) as countries approach/achieve polio-free status, to eliminate the residual risk from live vaccine strains while a country transitions away from OPV use.
Schedule: multiple doses given in infancy as part of the routine national immunization schedule (e.g., birth dose plus a primary series), often supplemented in endemic/high-risk countries by Supplementary Immunization Activities (SIAs) — periodic mass “Pulse Polio” campaign rounds providing additional OPV doses to all children under 5 regardless of prior vaccination status, a strategy central to India’s and other countries’ successful polio elimination efforts.
General sanitation measures: safe drinking water supply, proper sewage/excreta disposal, and hand hygiene — reducing faecal-oral transmission opportunities, complementing (though far less effective alone than) vaccination as the primary prevention strategy.
Surveillance: acute flaccid paralysis (AFP) surveillance in children under 15 years is a key pillar of global polio eradication programmes, allowing early detection of any residual wild poliovirus circulation or vaccine-derived poliovirus emergence.