Effect of the H1N1 and H3N2 <i>ca</i> vaccines on replication of the H5N1 HK03 <i>ca</i> virus in the upper respiratory tract of ferrets.

<p>Groups of ferrets were vaccinated with the indicated virus and four weeks later inoculated with the H5N1 HK03 <i>ca</i> vaccine. Antibody titers against homologous vaccine virus were determined by HAI assay and expressed as geometric mean titer. The H5N1 HK03 <i>ca</i> virus titer in nasal turbinates (NT) on day 3 post-inoculation is expressed as log₁₀EID₅₀ per gram of tissues calculated from the mean of 6 animals.