Fig 1. Stability of Subunit Vaccine in Liquid Formulations at 4°C (left) and 37°C (right).

Formulations were prepared with concentrated bulk H1N1 subunit vaccine (H1N1 California/07/2009 X179A). In addition to the stabilizers shown in the figure, all formulations contain 45 μg HA/mL, 20 mM phosphate buffer, 0.09% polysorbate 80 and 14 mM NaCl (F8 was in PBS which contained 140 mM NaCl). The formulations were stored at 4°C (A, left) and 37°C (B, right), and their HA titers were measured by SRID. Formulations were tested for up to 7 days. For screening, one dilution for each formulation was tested by SRID in triplicate. The data were presented as percentage recovery relative to the mean HA titer after formulation preparation (time 0) ± standard deviation of each triplicate. Abbreviations: SRID, single radial immunodiffusion; HA, hemagglutinin; PBS, phosphate buffer saline.