A model to evaluate mass vaccination against pneumococcus as a countermeasure against pandemic influenza

Abstract

A mathematical model has been developed for the purpose of evaluating vaccination against pneumococcus as a countermeasure against pandemic influenza. As the characteristics of a future pandemic cannot be known in advance, three distinct pandemic scenarios were considered, corresponding to a 1918-like pandemic, a 1957/1968-like pandemic and a 2009-like pandemic. Model estimates for each of these pandemic scenarios are presented for two options of vaccination programme; universal vaccination of the entire UK population and vaccination only of those people considered to be at heightened risk of developing influenza complications. We find that the benefits of each option (in terms of estimated number of deaths and hospital admissions avoided and the courses of antibiotics saved) are high in a 1918-like pandemic and very small in a 2009-like pandemic. Given that the decision regarding deployment of the counter measure would occur prior to knowledge of the flu-strain characteristics being available, we also present the weighted average of the outcomes from the three pandemic scenarios. Based on the historical occurrence of pandemics over the last 100 years, the weighted average of outcomes is an estimated 1400 deaths prevented by the universal vaccination option and 400 deaths saved by the targeted vaccination option (at a cost of approximately 400 million and 50 million courses of vaccine respectively). Finally, the longer term implications of using PPV as a countermeasure against pandemic influenza have been considered by estimating the expected number of courses of vaccine bought and the expected number of deaths and hospital admissions prevented over time under each policy.