Why did the American Academy of Pediatrics recommend switching from OPV to IPV in the United States?

• A. To eliminate VAPP and due to decreasing risk of wild-type poliovirus importation.
• B. To eliminate VAPP.
• C. To reduce cost per dose.
• D. To increase mucosal immunity.

Answer: (A)

The key idea is balancing safety with the type of immune protection a vaccine provides. OPV is a live, oral vaccine that gives strong gut (muttal) immunity and helps herd immunity, but it carries a rare risk of vaccine-associated paralytic poliomyelitis (VAPP) because the attenuated virus can revert and cause paralysis in the vaccinated person or spread to others. As polio near eradication and surveillance improves, the chance of wild-type poliovirus entering the country drops, so the benefit of using a live vaccine to boost mucosal immunity becomes smaller while the risk of VAPP remains. An inactivated vaccine (IPV) cannot replicate or revert, so it cannot cause VAPP, and it still protects against paralytic disease. Because the risk of importation has declined, switching to IPV minimizes the vaccine-caused risk without needing the mucosal boost that OPV provides.

The other options don’t fit the situation: reducing the cost per dose isn’t the driving reason—IPV is typically more expensive than OPV, and the goal wasn’t to cut costs. Increasing mucosal immunity isn’t achieved by IPV; OPV actually provides stronger mucosal immunity. Eliminating VAPP is part of the reason, but it’s specifically in the context of the reduced importation risk that makes switching to an inactivated vaccine sensible.