Abstract: A compound for protecting a vertebrate against infection by helminths comprising hyaluronidase covalently coupled to an immunostimulating carrier, in preferred form, the immunostimulating carrier to which the hyaluronidase is covalently coupled comprising a copolymer of ethylenepiperazine N-oxide and N-ethylacetylethylenepiperazinium bromide (hereafter referred to as "SYNPOL"), and a process for protecting a vertebrate against infection by helminths comprising administration to the vertebrate of a therapeutically effective amount of a compound comprising hyaluronidase covalently coupled to an immunostimulating carrier, preferably SYNPOL, in preferred form, the compound being administered to the vertebrate in the form of a vaccine.