Fig. 1

a. Efficacy Study 1 Experimental Design: Evaluation of vaccinated and non-vaccinated steers following contact with FMDV-infected steers. Top row: A total of 18 steers vaccinated with either a high, medium or low dose of AdtA24 vaccine and 4 naïve steers were co-mingled beginning 7 dpv with 8 steers that were directly infected with FMDV 24 h earlier (6 dpv). b. Efficacy Study 2: Experimental Design: Evaluation of vaccinated and non-vaccinated steers in contact with FMDV-exposed steers. Top row: 12 “primary (1^o) vaccinated and exposed” T2 steers were vaccinated with 5 × 10¹⁰ particle units of AdtA24 7 days prior to co-mingling with 10 T1 steers that were infected with FMDV via the intradermolingual (IDL) route on Day 0. The 10 T1 IDL-challenged ‘seeder’ steers were mingled with 12 T2 AdtA24 “1^o vaccinated and exposed” steers for 2 (n = 6 steers) and 3 days (n = 6 steers) and with 6 T3 “1^o naïve and exposed” steers for 2–3 days (3 steers for each day of duration). Bottom rows: for the next 41 days, 4 T4 2^o vaccinated + 6 T2 1^o vaccinated and exposed steers were in room 1; 4 T5 2^o naïve + 6 T2 1^o vaccinated and exposed steers were in room 2; 4 T6 2^o naïve + 6 T3 1^o naïve steers were in room 3