A modified dose-response model that describes the relationship between haemagglutination inhibition titre and protection against influenza infection.

AIMS: Develop a model for quantifying the risk of an adverse human response to influenza virus infection as a function of exposure dose and pre-exposure antibody titre level.

METHODS AND RESULTS: We evaluated the relationship between haemagglutination inhibition (HI) titre (as a measure of specific antibody response) and protection against influenza infection and modelled this relationship by incorporating HI titre as a variable into dose-response models. Using a maximum likelihood estimation approach, the resulting model was capable of providing statistically acceptable fits to most available data.

CONCLUSIONS: The incorporated HI titre dependency in the model quantifies the protective effect of antibody titre. The modelling can be used to predict the protection effectiveness associated with elevated HI titre levels post vaccination to different levels of exposures.

SIGNIFICANCE AND IMPACT OF THE STUDY: The study incorporates HI titre level as a variable into a dose-response model for influenza infection. The approaches developed in this study could be used to evaluate other factors associated with the predictability of HI titre or other surrogate endpoints for influenza vaccines.