Comparison of the clearance of radiolabelled nose drops and nasal spray as mucosally delivered vaccine

The distribution and nasal clearance of Tc-99(m)-labelled albumin (18.5 MBq), used as a mucosal vaccine surrogate for FluMist(TM), was determined in three volunteers. The subjects were randomized in a crossover clinical study design to receive either large-particle aerosal (nasal spray) followed by nose drops, or nose drops followed by the nasal spray, 1 week apart. Gamma scintigraphy was used to measure the distribution and clearance. The 'vaccine' delivered as drops was cleared from the nose into the oesophagus and upper stomach at very variable rates. In contrast, the nasal spray was uniformly distributed and cleared from the nasopharynx with a 50% mean clearance time of 50 min (range 40-60 min) and was not detected in the lungs. ((C) 1999 Lippincott Williams & Wilkins).