The present invention provides a composition comprising or consisting of inulin particles for use in the reduction or inhibition of inflammation, and/or for treating or preventing inflammatory disease, in a subject. Also provided is a pharmaceutically acceptable composition comprising: particles of inulin; and a substance comprising or consisting of one or more pathogen-associated molecular patterns (PAMPs), or an equivalent kit of parts, and methods and uses of the composition and kit for inducing or modulating an immune response in a subject, such as modulating an immune response to an antigen or allergen and/or as a vaccine. Also provided is a single-dose vaccine composition comprising inulin particles, an antigen and, optionally, an antigen-binding carrier material, and methods and uses of the vaccine.