Laboratory trials with inactivated vaccines against Escherichia coli (O2:K1) infection in fowls.

Laboratory trials were carried out with an O2:K1 vaccine prepared with either the Freund's complete or incomplete adjuvant. Both types of vaccine administered subcutaneously were highly effective against a challenge with the vaccine strain within three to four weeks after vaccination at two to three weeks of age. The complete adjuvant vaccine was more effective than the incomplete adjuvant vaccine when administered to chickens of an earlier age, and in the rate of development and duration of immunity. The efficacy of both vaccines was unimpaired by their incorporation with the Newcastle disease oil adjuvant (inactivated) vaccine (Newcadin). The use of an oil adjuvant vaccine was not found to affect the rate of growth adversely or to produce any other reaction prejudicial to its commerical application. The efficacy of the vaccines was unimpaired by their incorporation with Newcastle disease oil adjuvant (inactivated) vaccine (Newcadin) thus demonstrating the possibility of producing a combined Escherichia coli/Newcastle disease virus vaccine.