Oral immunization against pox. Studies on fowl pox as a model.

Oral vaccination against fowl pox is both effective and harmless. A suitable vaccine strain is the attenuated HP-1 strain in the 200th to 400th tissue culture passage. For optimal immunization virus of the 200th to 270th passage level should be applied twice at an interval of 3 to 4 weeks. Vaccination dose should contain 10(7.0)TCID50. Chickens may be effectively immunized already at 5 days. Immunity is against both homologous and heterologous virus and proves equally resistant to oral, cutaneous and intravenous challenge. Protection of mucous membranes of the upper respiratory and digestive tract forms faster than after cutaneous immunization. Compared to conventional fowl pox vaccination, drinking water vaccination facilitates the technicalities of vaccination; there are immunological advantages and risks of complications are avoided. It can therefore be recommended as a model for vaccination against smallpox in man.