Intranasal DNA Vaccine for Protection against Respiratory Infectious Diseases: The Delivery Perspectives

Xu, Yingying; Yuen, Pak-Wai; Lam, Jenny Ka-Wing

Despite the numerous merits of intranasal immunization, the potential hazard of nasal vaccines must not be overlooked. The concern of the safety of intranasal vaccination was raised after an intranasal inactivated influenza vaccine called NasalFlu, developed by Berna Biotech, was found to be associated with Bell's palsy, a temporary neurological paralysis of one side of the face [70] . NasalFlu consists of influenza virosomes which are formulated to contain hemagglutinin (HA) and neuraminidase (NA) antigens, as well as heat-labile enterotoxin (LT) from E. coli as mucosal adjuvant. Since parenteral administration of inactivated influenza vaccine did not confer an increased risk of Bell's palsy, nor the natural influenza virus infection, it was soon concluded that adjuvant LT from E. coli. was the culprit of these cases. For this reason, FluMist ® and NASOVAC ® -both are intranasal live-attenuated influenza vaccines without enterotoxin as adjuvants-do not appear to confer an increased risk for this condition.