Small-scale trials, in which eggs isolated from adult tapeworms were fed to up to 30 pigs, have already been conducted in Mexico, Peru, Cameroon and Honduras. The vaccine provided between 99.5 and 100 per cent protection in every trial. The Melbourne researchers, together with collaborators in Lima, Peru, now have plans for larger field trials in which the pigs will be allowed to forage as normal, they reported at a conference on parasitology in Melbourne last week. At the moment, two vaccinations about one month apart provide several months of immunity. The team's aim is to provide lifelong immunity with one or two shots, though they say the vaccine will still be beneficial even it has to be given yearly.
There is no reason why the vaccine would not work in people too. But safety issues make it much more costly to develop a human vaccine, and it should not be necessary, says Gauci. "An effective control programme would involve treating people with existing drugs to remove tapeworm from a population and preventing the reinfection of the human population by vaccinating pigs," he says.