Quick Hits

In the vaccine industry, squalene-based adjuvants are emulsions of squalene oil and water, often with additional surfactants or stabilizers. There are three primary types of squalene-in-water emulsions currently in use or widely studied as adjuvants:

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1. MF59
• Developer: Novartis (now GSK)
• Composition:
• 4.3% squalene
• 0.5% polysorbate 80 (surfactant)
• 0.5% sorbitan trioleate (Span 85)
• In citrate buffer
• Use: Licensed for use in seasonal and pandemic influenza vaccines (e.g. Fluad).
• Key Features: First oil-in-water emulsion adjuvant approved for human use.

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2. AS03
• Developer: GSK
• Composition:
• 10.69 mg squalene
• 11.86 mg DL-α-tocopherol (vitamin E) – enhances immune response
• 4.86 mg polysorbate 80
• Use: Used in H1N1 pandemic vaccines, some COVID-19 vaccine candidates.
• Key Features: More potent immune enhancer than MF59 due to tocopherol.

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3. AF03
• Developer: Sanofi
• Composition:
• Squalene
• Polysorbate 80
• Mannitol
• Cetyl phosphate
• Use: Investigational; used in some COVID-19 vaccine trials.
• Key Features: Less commonly used, still under development/testing.

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These three main formulations dominate current squalene-based adjuvant use in human vaccines. Variants or new formulations may be in preclinical stages, but MF59 and AS03 are the most widely studied and used.