Long-term solutions may involve vaccines given by mouth or by aerosol into the nose. Indeed, the new rotavirus vaccine expected to be licensed shortly to prevent diarrhea in infants will be administered by drops, like the Sabin oral polio vaccine. An influenza vaccine sprayed into the nose appears promising and may replace influenza vaccines now given by injection. Experimental oral cholera and salmonella vaccines might permit a variety of other diseases to be prevented by genetic engineering of these vaccines. Mice have been immunized by simply dropping liquid vaccines onto bare skin.
Vaccines produced in plants hold hope for inexpensive mass production and immunization by ingestion.
Encapsulation technologies to shield vaccines from the harsh acid environment of the stomach may permit vaccines now delivered by injection to be used orally. New vaccines are very expensive to develop, but those which do not require administration by needle and syringe may represent innovations well worth paying for. Return to the list of summaries.