Poliovirus Vaccination During the Endgame: Insights from Integrated Modeling
by Radboud J. Duintjer Tebbens and Kimberly M. Thompson, Expert Review of Vaccines2017; 16(6): 577-586, doi:10.1080/14760584.2017.1322514 (published on-line April 23, 2017).

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What are the study’s main findings?
What are the study’s main recommendations?
Background on polio

What are the study’s main findings?

• The success of the polio endgame depends on managing significant changes in the global demand and expected supply of different poliovirus vaccines. 
• Semi-finished oral poliovirus vaccine (OPV) (i.e., unlabeled vials) provides an option to store OPV for outbreak response with a longer shelf life than fully finished OPV and a shorter time to convert to fully finished OPV than bulk OPV.
• The long time delays and capacity constraints that occur in vaccine production complicate the management of major changes in vaccine demand (e.g., introduction or cessation of vaccines). Inactivated poliovirus vaccine (IPV) represents the only vaccine available for polio routine immunization after globally-coordinated OPV cessation, and production time and capacity constraints imply that full global introduction of IPV will not occur until 2018. The policy of rapidly ramping up trivalent OPV use before its cessation in 2016 created significant challenges with supply management.
• Management of a monovalent oral poliovirus vaccine (mOPV) stockpile for outbreak response after OPV cessation involves decisions about the total stockpile size and the timing of orders to convert bulk or semi-finished mOPV to readily-deployable fully finished mOPV with a shorter shelf-life.
• Based on estimated mOPV needs from 1,000 realizations of an integrated global model for long-term poliovirus risk management, we demonstrate the relationship between the stock-out probability and finished and total stockpile size.
• We illustrate how optimal stockpile ordering strategies and stock-out probabilities depend on the expected demand for each serotype, the time to convert bulk or semi-finished mOPV to fully finished mOPV, and the shelf-life of fully finished mOPV.
• The semi-finished mOPV option reduces the needed size of the fully finished stock and the expected loss of vaccine due to expiry.
• Assuming validity of the 1,000 realizations from the global model, our analyses suggest a considerably larger serotype 1 mOPV stockpile needed to achieve a 5% chance or less of a stock-out than the currently planned serotype 1 mOPV stockpile.
• The serotype 1 mOPV requirements exceed those for the two other mOPV serotypes, and the needed stockpile sizes exceed current plans for all three mOPV serotypes if we require less than a 1% (or 0.1%) chance of a stock-out.
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• Successful polio endgame management will require careful attention to poliovirus vaccine supplies.
• Insufficient vaccine supply could result in smaller immunization activities than needed and ultimately lead to greater demand and a need to restart OPV.  Minimizing this risk requires larger mOPV stockpiles than currently planned.
• In addition to maintaining a stockpile to cover expected mOPV demand for outbreak response, the Global Polio Eradication Initiative should consider maintaining additional stocks for the long-term in the event of a need to restart OPV, as well as an IPV stockpile for long-term risk management.
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