AF03, an alternative squalene emulsion-based vaccine adjuvant prepared by a phase inversion temperature method.

J Pharm Sci. 2012 Dec;101(12):4490-500.

Klucker MF, Dalençon F, Probeck P, Haensler J.

R&D Department, Sanofi Pasteur, Campus Mérieux, Marcy l’Etoile 69280, France.



AF03 is a squalene-based emulsion adjuvant that is present in the adjuvanted pandemic influenza vaccine, Humenza™. In this report, we describe the design and development of this novel adjuvant formulation from the selection of the oil and surfactant system used in the adjuvant composition to the phase inversion temperature emulsification process that afforded AF03 as a long-term stable and well calibrated oil-in-water emulsion. The emulsion was characterized by its particle sizes, surface and interfacial tensions, viscosity, and long-term stability. Copyright © 2012 Wiley Periodicals, Inc.

PMID: 22941944



With the exception of Alum, squalene emulsion-based vaccine adjuvants have been administered to far more people than any other adjuvant, especially in the context of the 2009-10 H1N1v influenza pandemic. The two most widely distributed squalene emulsion adjuvants are AS03 comprised in GSK’s Pandemrix®, Arepanrix® and Pumarix® and MF59 in Novartis’ FluAd®, Focetria®, Celtura® and Aflunov®. Both of these emulsion adjuvants are prepared by microfluidization, a high pressure, high energy, homogenization process [1].

With the introduction of the AF03 adjuvant, we showed that it was possible to prepare a similar type squalene-in-water emulsion by using a very simple, cost effective and readily scalable method known under the name of Phase Inversion Temperature (PIT) method. In this case, a crude oil-in-water mixture is turned into a very fine and long term stable oil-in-water emulsion by a simple heating and cooling cycle. This process is based on the unique properties of a particular class of etoxylated non-ionic surfactants (i.e. polyoxyethylene-12 cetostearylether in AF03) that transition from a micellar phase to an inverted micellar phase upon heating above the transition temperature, and vice versa upon cooling below the transition temperature, creating a stable and uniform emulsion when comprised in appropriate concentration in an oil and water mixture.

This process was used to produce a concentrated squalene-in-water emulsion (32.5% squalene) which was then diluted to 5% squalene to yield the AF03 adjuvant formulation.

AF03 was found to be safe and efficacious in a number of human vaccine trials using pandemic influenza strains [2,3] and was used in the development of Sanofi Pasteur’s adjuvanted H1N1v influenza vaccine, Humenza®.



  1. Fox CB, Haensler J. An update on safety and immunogenicity of vaccines containing emulsion-based adjuvants. Expert Rev Vaccines. 2013; 12(7):747-58.
  2. Haensler J. Introduction to novel vaccine adjuvants and their role in influenza vaccination. Ann Pharm Fr. 2013; 71(2):104-8.
  3. Vesikari T, Pepin S, Kusters I, Hoffenbach A, Denis M. Assessment of squalene adjuvanted and non-adjuvanted vaccines against pandemic H1N1 influenza in children 6 months to 17 years of age. Hum Vaccin Immunother. 2012; 8(9):1283-92.


Jean Haensler-1Figure 1. Principle of PIT method for the production of AF03

A crude squalene-in-water emulsion is created at 40°C by mixing PBS containing polyoxyethylene-12 cetostearylether with squalene containing sorbitan oleate. The crude emulsion is then inverted into a water-in-oil emulsion by heating at 70°C which is above the PIT of the system (~65°C). Then, heating is turned off, and as the temperature decreases below the PIT, a fine, concentrated, oil-in-water emulsion is formed. The process is typically monitored in line by using a conductimetry (or a pH) probe, as oil-in-water emulsions conduct electric current and water-in-oil emulsions do not. AF03 is obtained by further dilution of the concentrated bulk emulsion with PBS to 5% of squalene. When used as vaccine adjuvant, AF03 is typically mixed vol/vol with the antigen solution.

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