Virus clearance study

Scaled-down studies in which purification steps, such as low-pH hold, solvent/detergent treatment, chromatography and virus filtration, are spiked with model viruses to measure how far each step reduces or inactivates them. Results are expressed as log reduction values for each step and in total, and they support the viral safety claim in the application. Studies use qualified scale-down models and model viruses with different sizes and envelope types, for example a small non-enveloped parvovirus and an enveloped retrovirus. Steps based on the same mechanism are not counted twice.