Safic-Alcan is a specialist in adjuvants and excipients used for vaccine formulations, supporting pharmaceutical manufacturers in the development of safe, effective and stable vaccines.
The formulation of a vaccine plays a critical role in determining its efficacy, safety, stability and shelf life. Beyond the active ingredient, vaccines contain several additional components that ensure optimal immune response, product integrity and patient safety.
Understanding Vaccine Formulations
Vaccines can be broadly classified into two main categories, depending on how the antigen is produced.
Attenuated vaccines
Attenuated vaccines are composed of a live pathogen that has been rendered harmless. These vaccines typically generate a strong and long-lasting immune response on their own and generally do not require adjuvants or complex excipient systems.
Inactivated and subunit vaccines
Inactivated vaccines are made from killed pathogens or antigenic fragments. Because these antigens alone may not elicit a sufficient immune response, these vaccines require adjuvants and excipients to ensure effectiveness and stability.
In such formulations:
- Adjuvants enhance and direct the immune response
- Excipients stabilize, protect and preserve the antigen throughout the product’s shelf life
1. Vaccine Adjuvants
Adjuvants are critical components that improve vaccine performance by enhancing antigen presentation and immune activation.
a. Aluminum-based adjuvants
Aluminum salts are the most widely used vaccine adjuvants, with more than 80 years of clinical use. They promote a slow release of the antigen and improve uptake by the immune system.
The two main forms used in vaccines are:
- Aluminum hydroxide (aluminum oxyhydroxide, AlOOH)
- Aluminum hydroxyphosphate (AlOHPO₄)
Aluminum hydroxide is the most commonly used. These adjuvants are produced by exposing aqueous solutions of aluminum salts (sulfates or chlorides) to carefully controlled alkaline conditions — making the choice of excipients particularly important during formulation.
b. Oily adjuvants
Oily adjuvants enable the formulation of vaccine emulsions, in which the antigen is present in an aqueous phase. These emulsions can take several forms:
- Oil-in-water (O/W)
- Water-in-oil (W/O)
- Multiple water-in-oil-in-water (W/O/W) emulsions
Each emulsion type offers different safety, stability and efficacy profiles, allowing formulators to tailor immune responses for specific applications.
c. Lipid nanoparticles (LNPs)
Lipid nanoparticles are ionizable lipid systems designed to encapsulate and protect antigens. They are a key technology in mRNA vaccines, enabling efficient delivery of genetic material into target cells while protecting it from degradation.
2. Vaccine Excipients
Excipients are non-active ingredients that play a fundamental role in maintaining vaccine quality, safety and usability.
a. Diluents
Diluents are liquids used to dilute vaccines to the appropriate concentration prior to administration.
The most commonly used diluent is sterile water for injection.
b. Preservatives
Preservatives prevent microbial contamination after a vaccine vial has been opened, particularly in multi-dose vials. Single-dose vaccines may not require preservatives and are discarded after use.
Common preservatives include:
- Formaldehyde (used during and after production to inactivate microbes)
- Phenol and phenoxyethanol
- Benzalkonium chloride
- Sodium metabisulfite
c. Stabilizers
Stabilizers protect vaccines from chemical degradation and prevent antigens from adhering to vial surfaces. They help maintain vaccine quality throughout storage and transport.
Stabilizing agents may include:
- Sugars (e.g. sucrose), contributing to viscosity and stability
- Amino acids (e.g. glycine)
- Gelatin and proteins (such as recombinant human albumin derived from yeast)
- Glycerin, which acts as a solvent while improving viscosity and stability
3. Buffering Agents
Buffer agents are used to maintain pH balance, ensuring vaccine compatibility with physiological conditions.
Common buffering agents include:
- Sodium chloride
- Potassium chloride
- Sodium hydroxide
- Succinic acid
- Sodium bicarbonate
- Sodium carbonate
Maintaining the correct pH is essential to preserve antigen integrity and ensure patient safety.
Supporting Vaccine Innovation with Safic-Alcan
Safic-Alcan supports vaccine manufacturers with a reliable portfolio of high-quality adjuvants and excipients, designed to meet the stringent requirements of pharmaceutical development and regulatory compliance.
Our expertise helps formulators:
- Enhance immune response
- Improve formulation stability
- Extend shelf life
- Ensure consistent vaccine performance