A prophylactic regimen for passively preventing infection with a pathogen which has a typical route of infection through the nasopharynx region of a subject, e.g., an airborne virus typically transmitted through coughing or sneezing. The method involves specifically targeting a subject's nasopharynx with a viral vector comprising an AAV capsid and carrying a nucleic acid sequence encoding an anti-viral neutralizing antibody construct operably linked to expression control sequences, in order to provide for high levels of expression of the anti-viral neutralizing antibody construct in the nasal airway cells. Optionally, the neutralizing antibody construct is expressed under a promoter which is regulated or induced by a small molecule which is delivered separately from the viral vector. In one embodiment, the method permits transfection of a subject's nasopharynx even where the subject has circulating neutralizing antibodies against the AAV capsid.