Decision analysis in planning for a polio outbreak in the United States

Global eradication of poliomyelitis may soon be achieved, but circulating polioviruses could reemerge years after eradication by reversion of live attenuated oral vaccine virus to a virulent form, laboratory stock mishandling, or bioterrorism. If a poliomyelitis outbreak occurs in the United States, access to a vaccine stockpile to interrupt viral spread will be necessary. Options for the stockpile include the inactivated polio vaccine and the live-attenuated trivalent and monovalent oral poliovirus vaccines. With differences in immunogenicity, adverse effects, availability, and other issues, the optimal vaccine choice for the stockpile is not clear. We sought to compare vaccine interventions for poliomyelitis outbreak control.

We applied decision analysis to 8 strategies for outbreak control: no intervention, 1 or 2 inactivated polio vaccine doses, 1 or 2 trivalent oral poliovirus vaccine doses, 1 or 2 monovalent oral poliovirus vaccine doses, and sequential inactivated polio vaccine-monovalent oral poliovirus vaccine. Historical data from outbreaks in developed countries were used to estimate the risk of paralytic disease after a hypothetical reintroduction of circulating polioviruses. The outcome measure was cases of paralytic poliomyelitis.

Monovalent oral poliovirus vaccine provided optimal outbreak control in most scenarios because of high seroconversion rates with 1 dose. Control provided by trivalent oral poliovirus vaccine and inactivated polio vaccine was equivalent at high vaccine coverage rates. At low intervention rates, trivalent oral poliovirus vaccine produced fewer paralytic cases than inactivated polio vaccine in highly immune populations but more cases than inactivated polio vaccine in poorly immunized groups because of secondary transmission of oral poliovirus vaccine virus and vaccine-derived viruses.

This model suggests that monovalent oral poliovirus vaccine would be the most advantageous vaccine for outbreak control. If a monovalent oral poliovirus vaccine stockpile is impractical, the optimal vaccine choice depends on the previous immunity and the anticipated intervention rates.