What is a key safety concern of OPV vaccination?

• A. Allergic reactions
• B. Minimal adverse effects
• C. Potential for vaccine-associated paralytic poliomyelitis (VAPP) and vaccine-derived poliovirus (VDPV) outbreaks
• D. Only fever

Answer: (C)

Oral polio vaccine uses a live, attenuated virus that can replicate in the gut and provide strong mucosal immunity, but this live virus can occasionally revert to a neurovirulent form. In a vaccine recipient or in close contacts, this reversion can cause vaccine-associated paralytic poliomyelitis. If the attenuated virus spreads in under-immunized communities, it can continue circulating and accumulate mutations, leading to circulating vaccine-derived poliovirus outbreaks. These VAPP and VDPV risks are the main safety concerns with OPV, which is why vaccination strategies weigh them against its practical benefits and, in many places, shift toward vaccines that cannot cause such derivatives.