Kaplan–Meier plots indicating the survival of A/J mice after passive transfer of naïve and immune goat sera at different dilutions. For each group (undiluted and diluted), 500 µL of serum from each goat subject (n = 5) were inoculated into three A/J mice (n = 15 for each group). Positive control mice (n = 12, three A/J mice per goat) received undiluted sera from immune goats (n = 4) that survived a virulent B. anthracis challenge. Negative control mice (n = 9, three A/J mice per goat) received undiluted sera from naïve goats (n = 3). The mice were lethally challenged after 24 h with 1.92 × 105 spores per dose from the Sterne 34F2 vaccine strain.