The aim of viral clearance studies is to assess the ability of a downstream process to remove and/or inactivate viruses. This ability is assessed by spiking a down-scale of the manufacturing process.

Start material is spiked with virus and the scaled-down process step is performed. The different fractions are collected and titrated. The Reduction Factor (RF) is calculated (difference between the initial viral load and the final viral load).

“Log reductions of the order of 4 logs or more are indicative of a clear effect with the particular test virus under investigation.” (CPMP/BWP/268/95)