Image of an immune cell

What is an adjuvanted vaccine?

The purpose of adjuvants

Adjuvants are a diverse group of substances used to enhance the immune response to a vaccine (i.e. improve the vaccine’s immunogenicity).1,2

How do adjuvants work?

The word adjuvant comes from the Latin ‘adjuvare’, meaning ‘to help’ or ‘to aid’.4 Different adjuvants have different modes of action.3

For example, some adjuvants provide danger signals, in a similar way to endogenous mediators released in response to infection or injury, that stimulate a more robust innate immune response together with an antigen.1 Other adjuvants may interact with antigen-presenting cells and trigger a localised release of immune signalling molecules, such as cytokines and chemokines, or help make an antigen more visible to the immune system.3

Appropriate selection of adjuvants is key to developing efficacious and novel vaccines, as no single adjuvant covers all vaccine needs.3

Watch the video on ‘Understanding adjuvant mode of action in vaccines’ to find out how…

  • A vaccine containing a purified antigen alone may have limited or no triggers essential for generation of the innate immune response, meaning the innate immune response may be mild and insufficient to induce effective adaptive immunity3
  • Adding an adjuvant, which mimics immune response triggers, to a vaccine can help elicit transient activation of the innate immune response, enhancing recruitment of innate immune cells and activation of antigen-presenting cells, such as dendritic cells3
  • Appropriately activated dendritic cells confer long-lasting adaptive immunity via the ensuing T- and B-cell responses and induction of memory cells3

Commonly used adjuvants

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Aluminium salts

Aluminium salts, or alum, are the adjuvant type used in vaccines for the longest period of time (more than 80 years) and are extensively used.1,3 Antigens are adsorbed onto the surface of aluminium salts, and this binding enhances antigen uptake and presentation by antigen-presenting cells.5

NA

Emulsions

Water-in-oil emulsions such as MF59 are able to carry antigens and stimulate the innate immune response.5 An example of a vaccine which uses MF59 is the inactivated influenza vaccine.5

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Immune potentiators

An example of an immune potentiator is flagellin.5 Flagellin is a component of bacteria recognised by immune cells that express a receptor called toll-like receptor 5 (TLR5).5 Flagellin is capable of activating inflammatory pathways and evoking helper T-cell responses.5

Immune potentiators have been used to develop vaccines against influenza, plague and tuberculosis.5

The benefits of adding an adjuvant to a vaccine include the following:

Enhancing the immune response to vaccine antigens3

NA
  • Adjuvants enable highly purified antigens that lack intrinsic immune triggers to be used in vaccines
  • Adjuvants may lead to faster, elevated and broader immunity
  • Adjuvants may lead to longer-lasting immunity with fewer booster doses needed

Improving the immune response in certain populations3

NA
  • Adjuvants may lead to enhanced and effective immune responses in populations such as elderly or immunocompromised patients who may otherwise have weaker immune responses

Enabling sparing of the antigen component of a vaccine3

NA
  • Adjuvants may allow smaller amounts of the antigen to be included in the vaccine formulation, enabling antigen sparing, which is particularly relevant during pandemics

References

  1. Pollard AJ and Bijker EM. A guide to vaccinology: From basic principles to new developments. Nat Rev Immunol 2021;21:83–100.
  2. Verma SK et al. New-age vaccine adjuvants, their development, and future perspective. Front Immunol 2023;14:1043109.
  3. Garçon N et al. Vaccine adjuvants. In: Garçon N, Stern PL, Cunningham AL, Stanberry LR, editors. Understanding modern vaccines: Perspectives in vaccinology. Amsterdam: Elsevier; 2011. 89–113.
  4. Apostólico JdS et al. Adjuvants: Classification, modus operandi, and licensing. J Immunol Res 2016;2016:1459394.
  5. Facciola A et al. An overview of vaccine adjuvants: Current evidence and future perspectives. Vaccines (Basel) 2022;10:819.

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June 2024 | NP-GB-ABX-WCNT-240004 (V1.0)