Passive immunization with a recombinant adenovirus expressing an HA (H5)-specific single-domain antibody protects mice from lethal influenza infection

► An adenoviral vector efficiently expresses anti-influenza virus-neutralizing single-domain antibodies. ► An adenovirus with single-domain antibodies gene efficiently prevents influenza virus infection. ► A single-domain antibodies efficiently prevent and treat influenza virus infection. ► A combination of single-domain antibodies and its gene expands the time of protection against influenza.