Hypothetical emergence of poliovirus in 2020: part 2. exploration of the potential role of vaccines in control and eradication.

ABSTRACT

OBJECTIVES: The emergence of human pathogens with pandemic potential motivates rapid vaccine development. We explore the role of vaccines in control and eradication of a novel emerging pathogen. METHODS: We hypothetically simulate emergence of a novel wild poliovirus (nWPV) in 2020 assuming an immunologically naïve population. Assuming different nonpharmaceutical interventions (NPIs), we explore the impacts of vaccines resembling serotype-specific oral poliovirus vaccine (OPV), novel OPV (nOPV), or inactivated poliovirus vaccine (IPV). RESULTS: Vaccines most effectively change the trajectory of an emerging disease when disseminated early, rapidly, and widely in the background of ongoing strict NPIs, unless the NPIs successfully eradicate the emerging pathogen before it establishes endemic transmission. Without strict NPIs, vaccines primarily reduce the burden of disease in the remaining susceptible individuals and in new birth cohorts. Live virus vaccines that effectively compete with the nWPVs can reduce disease burdens more than other vaccines. When relaxation of existing NPIs occurs at the time of vaccine introduction, nWPV transmission can counterintuitively increase in the short term. CONCLUSIONS: Vaccines can increase the probability of disease eradication in the context of strict NPIs. However, successful eradication will depend on specific immunization strategies used and a global commitment to eradication.