OBJECTIVES: The time required for influenza vaccine production means that there is a delay between the World Health Organization (WHO) seasonal vaccine strain recommendations and vaccine distribution (six months). This can cause a mismatch between vaccine strains and circulating strains due to antigenic drift which could potentially reduce vaccine effectiveness (VE). The impact of delaying WHO recommendations nearer to the time of vaccine distribution on VE is not understood, and so a new approach is required to bridge this gap.

METHODS: A targeted literature review was conducted to summarize the WHO’s vaccine strain selection process. Keyword searches in PubMed identified published papers reporting on the strain selection process. Databases and committee papers from the WHO vaccine selection group were identified through grey literature searches. Using the extracted information, a novel approach was developed to mimic the WHO’s vaccine strain selection process for the Value of Time (VoT) analysis.

RESULTS: The literature review identified seven criteria for decision-making: antigenic, genetic, serology, epidemiological, VE, candidate vaccine virus and fitness forecasting although the weighting given to each criterion by the WHO is unclear. A regression analysis is proposed to generate an algorithm to mimic the vaccine strain selection process and determine the “optimized strain” based on historical data available. The complexity of this analysis is dependent on data availability. The outputs would allow a relative improvement in VE to be estimated through a “goodness of selection” variable.

CONCLUSIONS: The VoT analysis provides a data dependent methodology that mimics the vaccine strain selection process through regression analyses when delaying vaccine virus strain selection. Estimating the relative VE of the optimized vaccine versus chosen strain (while recognizing the assumptions and limitations) could inform an economic model to estimate the impact of time delay on clinical and economic outcomes.