Serum trough concentrations for motavizumab and palivizumab. Data shown are mean (SD). The peak serum trough concentrations for each group reflect the sequence of dosing for that treatment group. Final serum concentrations (days 270-300) reflect those assessed 120-150 days after the final dose. Serum trough concentrations below the lower limit of quantification (motavizumab, 1.563 μg/mL; palivizumab, 10 μg/mL) were reported as 0.