Many vaccines create immunity to viral diseases by introducing a certain portion of the disease-causing virus' s outer coating into the body  Exposure to that part of a virus is as effective as exposure to the whole virus in stimulating production of antibodies that will subsequently recognize and kill the whole virus  To create a successful vaccine of this type, doctors must first isolate in the disease-causing virus a portion that stimulates antibody production
Now that a suitable portion of the virus that causes hepatitis E has been isolated, doctors claim they can produce a vaccine that will produce permanent immunity to that disease
Some laboratory animals exposed to one strain of the hepatitis virus developed immunity to all strains of the virus.