Figure 4. Human serum antibodies detecting HAC1. HAC1 detecting IgG antibodies were measured by ELISA on serum collected pre vaccination and at 7, 14 and 21 d (d) and 3, 6 and 12 mo (m) post vaccination. Each symbol represents one individual serum sample. Lines represent the mean ± standard error of the mean (SEM). ** and *** indicate concentrations significantly different from day 0 with p < 0.005 and p < 0.0005, respectively. The number of sera (n) included at each time point is indicated.