VLP yields vary widely by expression system. Yeast achieves 50-700 mg/L in fed-batch, insect cells produce 10-200 mg/L, E. coli yields 50-400 mg/L but often requires refolding, and mammalian cells yield 5-50 mg/L. The insect cell baculovirus expression vector system (BEVS) is the most widely used for licensed VLP vaccines.

Total crude VLP yield (mg) = culture volume (L) x volumetric productivity (mg/L). The purified yield is calculated by multiplying the crude yield by the recovery percentage at each downstream step. A typical process achieves 40-70% overall recovery.

Seven licensed VLP vaccines span four expression platforms: Gardasil 9 (HPV, yeast), Cervarix (HPV, insect cell), Engerix-B and Recombivax HB (HBV, yeast), Hecolin (HEV, E. coli), Mosquirix (malaria, yeast), and Nuvaxovid (COVID-19, insect cell).

Modern VLP purification uses a scalable chromatographic platform: depth filtration for clarification, TFF (300-500 kDa MWCO) for concentration, AEX for capture, SEC or multimodal chromatography for polishing, and 0.2 um sterile filtration. This replaces ultracentrifugation and scales linearly to thousands of litres.

VLP vaccines typically contain 20-80 ug antigen per dose. A 200L insect cell bioreactor producing 100 mg/L with 45% purification recovery yields about 9,000 mg purified VLP, providing 150,000 to 450,000 single doses. This high output per batch makes VLP vaccines cost-effective for global immunization.

Non-enveloped VLPs (HPV L1, HBsAg) are robust capsid-only structures tolerating pH extremes and moderate shear. Enveloped VLPs (influenza HA/NA) incorporate a lipid bilayer and are fragile, requiring gentle processing, polysorbate 80, and cryoprotectants for stability.