Oral immunization of dogs against tetanus, diphtheria and pertussis.

Mongrel dogs were revaccinated three weeks after basic parenteral immunization with a DT-vaccine with 3 X 3 capsules of an enteric coated oral vaccine, which contained 500 Lf in each of the capsules. When there was a basic titer of 0.005 IU/ml serum, the titer went up to 10 IU/ml by oral vaccination. Similar levels were obtained when lozenges containing the same amount of toxoid were used for revaccination. A twofold buccal vaccination without preceding parenteral vaccination yielded no protective titers. Also a parenteral basic immunization with a diluted DPT-vaccine, followed by oral vaccination with enteric coated capsules, containing a soluble pertussis vaccine, resulted in no titers measured by bacterial agglutination test. In the cases of diphtheria and tetanus only part of the animals showed elevated titres after oral vaccination and protective titers could only be reached if rather high amounts of toxoids were administered orally. It can be concluded from the results that an oral revaccination does not confer protective immunity comparable to that conferred by parenteral vaccination.