Which statement accurately reflects the estimated risk of VAPP per OPV dose?

• A. Approximately 1 in 1 million doses.
• B. Approximately 1 in 10 million doses.
• C. Approximately 1 in 3 million doses.
• D. Approximately 1 in 2.5 million doses.

Answer: (D)

VAPP risk per OPV dose is exceedingly small because it relies on a rare event: the attenuated virus in the vaccine reverting to a neurovirulent form and causing paralysis. Surveillance data have estimated this rate by comparing reported VAPP cases to the total number of OPV doses given. The best-supported figure used in many guidelines is about one VAPP case per 2.5 million OPV doses. So, when you look at millions of doses being given, you’d expect roughly one such case in that many doses on average. This tiny risk is weighed against the substantial benefits OPV provides in interrupting transmission in populations at risk. While other estimates exist, 1 in 2.5 million aligns most closely with the standard surveillance-derived figure.