Which of the following is NOT a factor in deciding to use mOPV2 in outbreak response?

• A. Seizure risk of re-emergence of type 2 poliovirus
• B. Current immunity levels
• C. Genetic lineage of circulating strains
• D. Global stock of OPV vaccines

Answer: (D)

When evaluating whether to use mOPV2 in an outbreak, the focus is on the biological and epidemiological risk. The concern about re-emergence of type 2 poliovirus is central because mOPV2 carries type 2; if the vaccine-derived virus can revert and spread in under-immunized groups, it could spark new outbreaks. Current immunity levels in the population matter because strong immunity to type 2 reduces transmission risk and the chance that vaccination will backfire, while low immunity makes spread more likely. The genetic lineage of circulating strains helps determine the nature of the outbreak—whether it’s a vaccine-derived lineage that might respond to the intervention, or a different circulating strain with different implications—which in turn influences how effective mOPV2 will be and what risks it carries. Global stock of OPV vaccines, while important for how quickly and broadly a response can be executed, is an operational consideration rather than a driver of whether the vaccine is appropriate from a public health risk standpoint.