Calcium phosphate: a substitute for aluminum adjuvants?

ABSTRACT

Introduction: Calcium phosphate was used as an adjuvant in France in diphtheria, tetanus, pertussis and poliomyelitis vaccines. It was later completely substituted by alum salts in the late 80’s, but it still remains as an approved adjuvant for the World Health Organization for human vaccination.

Area covered: Thus, calcium phosphate is now considered as one of the substances that could replace alum salts in vaccines. The aim of this paper is to draw a review of existing data on calcium phosphate as an adjuvant in order to bring out the strengths and weaknesses for its use on a large scale.

Expert commentary: Calcium phosphate is a compound naturally present in the organism, safe and already used in human vaccination. Beyond comparisons with the other adjuvants, calcium phosphate represents a good candidate to replace or to complete alum salts as a vaccine adjuvant.

KEYWORDS:

• Vaccine
• adjuvant
• calcium phosphate
• safety
• immune response
• aluminum salts

Acknowledgments

We are grateful to E & R Jandot for their careful revision and critical comments on this paper.

Declaration of interest

The authors have no relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript. This includes employment, consultancies, honoraria, stock ownership or options, expert testimony, grants or patents received or pending, or royalties.

Documentary research methodology

The aim of this study has been to make an international state of the art about the use of calcium phosphate as an adjuvant in vaccine. Exhaustive documentary research has been conducted in order to establish a quantitative and qualitative usable data assessment. All published data concerning advantages and disadvantages of the use of calcium phosphate have been sought. Points of View or recommendations on the inclusion of the calcium phosphate in vaccines or more broadly on the adjuvant safety have been identified. Documentary sources database, grey literature, relevant internet sites as well as (French) regulatory information have been sorted, assessed and interviewed in a systematic way. The recommendations, meta-analysis and systematic reviews have been sought in Medline from key words: (‘Adjuvants, Immunologic’[Mesh] OR Adjuvant*) And (vaccine* Or immunol*)[title] then scientific publications on the use of calcium phosphate as adjuvant from key words: ‘Calcium phosphate’ [Supplementary Concept] OR ‘Calcium Compounds’[Mesh] OR ‘Calcium Phosphates’[Mesh] OR calcium phosphate Or CaP Field: Title AND (‘Adjuvants, Immunologic’[Mesh] or adjuvant* Field: Title). 160 references, with various quality and relevance, have been obtained on the basis of this research and a hundred of them have proved workable.

Additional information

Funding

This work has been carried out with E3M association with the financial support of Mutuelle Familiale.