Chris Bowman

(Department of Mathematics, National Research Council Institute for Biodiagnostics, Winnipeg and Electrical and Computer Engineering, University of Manitoba)

Evaluation of Vaccination Strategies during Pandemic Outbreaks

Date Tuesday, November 3, 2009

During a pandemic, several factors could significantly impact the outcome of vaccination campaigns, including the delay in pandemic vaccine availability, inadequate protective efficacy, and insufficient number of vaccines to cover the entire population. The efficacy of a poor vaccine can be boosted by delivering a second dose of the same vaccine at a later time. We incorporate these factors into a novel vaccination model with a fixed delay between first and second doses to investigate and compare the effectiveness of the single-dose and two-dose vaccine strategies. If vaccination starts early enough after the onset of the outbreak, a two-dose strategy can lead to a greater reduction in the total number of infections. This, however, requires the second dose of vaccine to confer a substantially higher protection compared to that induced by the first dose. For a sufficiently long delay in start of vaccination, the single-dose strategy outperforms the two-dose vaccination program regardless of the increase in protective benefit from the second dose. The findings suggest that the population-wide benefits of a single-dose strategy will in general be greater than the two-dose vaccination program, in particular when the second dose offers marginal increase in the protection induced by the first dose.