Influenza A antibody results by study day and group based on ELISA assay.

Competitive Nucleoprotein-based IDEXX ELISA (Influenza A antibody). Ratios <0.60 classified as positive; ratios ≥0.60 classified as negative.
ND = Not done; IDEXX Inc. = Commercial ELISA assay (note the lower the ratio, the greater the antibody detected); Ch = challenge.
aWhere numbers tested differ from the number randomized per group in parentheses at the specified time point it is because insufficient sera remained for testing of all animals.
bNumber of sera tested by group shown in adjacent columns.
cOne day 0 serum in each group was insufficient for ELISA testing and substituted with pre-shipment values for these ferrets. Excluding these ferrets (leaving n = 15 per group) gives ELISA ratios of 1.04 (0.99–1.09) and 1.05 (1.01–1.09) for vaccine and placebo groups, respectively.
dTwo sera belonging to placebo group close to serologic threshold for positivity with ratios of 0.61.