Vaccination composition

A method to prepare a vaccine composition comprising a particle comprising a polymer matrix that covalently incorporates an adjuvant and/or antigen, which method comprises:

• (i) mixing an antigen and/or adjuvant comprising a first reactive moiety with an aqueous solution or dispersion comprising polymer chains, said polymer chains comprising at least one second reactive moiety capable of reacting with said first reactive moiety, wherein the first reactive moiety may be attached to the antigen and/or adjuvant through a linker and/or the second reactive moiety may be attached to the polymer through a linker and the polymer chains further being capable of cross-linking directly with each other intra- or intermolecularly;
• wherein said polymer chains are subjected to conditions so as to self-assemble into particles either before or after said mixing, thereby entrapping said antigen and/or adjuvant non-covalently;
• thus obtaining the antigen and/or adjuvant encapsulated non-covalently in the particles;
• (ii) subjecting the particle mixture of step (i)
• (a) to cross-linking forming a particulate polymer matrix wherein the crosslinks of said matrix are independent of said antigen and/or adjuvant and
• (b) to conditions wherein said first and second reactive groups form covalent bonds so that the adjuvant and/or antigen is covalently bound to the particulate polymer matrix and entrapped therein wherein said adjuvant and/or antigen has only one first reactive moiety;
• wherein in step (ii) the crosslinking is performed without a free radical initiation and/or wherein the crosslinking is non-self-propagating.