What is a significant disadvantage of IPV compared with OPV?

• A. IPV is given orally and easier to administer.
• B. IPV is given as a nasal spray.
• C. IPV vaccine-induced immunity in the gut is higher than OPV.
• D. IPV induces very low levels of immunity in the intestines, allowing wild poliovirus to multiply.

Answer: (D)

A primary concept here is how different vaccines shape immunity in the gut. OPV is a live attenuated vaccine taken by mouth, so it replicates in the intestinal tract and stimulates mucosal immunity there. This gut immunity includes local antibodies and memory that help block replication and shedding of poliovirus if someone is exposed, which is key for interrupting transmission.

IPV, on the other hand, is inactivated and given by injection. It creates strong systemic antibodies that protect against paralytic disease, but it doesn’t provoke strong mucosal immunity in the intestines. As a result, after exposure to wild poliovirus, the virus can still replicate in the gut and be shed, even in vaccinated people.

That difference—poor intestinal immunity with IPV compared to the gut immunity boosted by OPV—explains why IPV is a disadvantage when it comes to stopping transmission. The other statements are incorrect because IPV is not given orally or as a nasal spray, and its gut immunity is not higher than OPV.