Standard Vaccine Adjuvants

SPI Pharma offers a range of aluminum hydroxide gel VAC grades for adsorption (pseudo-boehmite form) for use as a vaccine adjuvant. It is used to bind negatively charged antigens.

VAC Gels are able to adsorb a large range of proteins and inactivated bacteria/viruses. At pH of preparation of vaccines around 5-7, Pseudo-Boehmite gels have the property to:

  • Adsorb negatively charged antigens
  • Slow the release of a inactivated virus or bacteria
  • Activate and stimulate the immune response
  • Create a more rapid development of high tittered and long-lasting antibody responses after primary immunization

Following is: SPI’s Range of Aluminum Hydroxide Gels (VAC Gels) 

Product Name

Assay Al2O3 %
Aluminum stated on the label


VAC 15



VAC 20



VAC 30



Sterilized grades by gamma irradiation are available upon request.

Adsorbent properties are related to surface area and surface groups. The hydroxyl groups can accept a proton (positive charge) and donate a proton (negative charge): 

VAC Proton

Schematic of the structure of the gel. When the surface of the aluminum oxyhydroxide is positive, it attracts negatively charged antigens. Adsorption capacity is determined by surface area and surface charge from the hydroxyl groups.

Adjuvants surface chargeAluminum hydroxide adjuvants' surface charge is pH dependent. At physiological pH around 5.0-7.0, Pseudo-Boehmite gels have the property to adsorb negatively charged antigens. Zerio point charge (ZPC) is around pH 10.2.

Related Applications

Vaccine Adjuvants

Vaccine Adjuvants

SPI Pharma supplies aluminum hydroxide vaccine adjuvants to enhance and help the ability of your antigen to stimulate the immune system.

Related Resources

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