Protective immunity is a primary goal in the development of ontiparositic vaccines. Often however, parasite immunologists are faced with chronic infections that apparently do not induce a protective immune response. But although epitopes presented by some parasites may fail to induce protective immunity, there may be other antigens normally concealed from the host that, if revealed, could stimulate the required response. Indeed, there is evidence that some drugs — such as praziquantel — can act in this way, by revealing hidden parasite antigens that then induce the protective response. Vaccination with ‘concealed’ antigens is already being developed to control ectoporasitic ticks (see Parasitology Today 4,196–198). This article suggests a similar approach for hookworm vaccines, by which a ‘first-wave’ attack would be stimulated by surface antigens, followed by a ‘second-wave’ attack directed against the underlying cuticular collagens o f the parasite.