Table 3.

Protective efficacy of dk/Sing (H5N3) vaccine against lethal infection with HK/483 virus

Vaccine groupPrechallenge antibody titera against:Mean virus titer (log10 EID50/ml) ± SDbNo. protected/total no.c
HK/156HK/483
HINeutralizationHINeutralizationLungBrainInfectionDeath
dk/Singd 80400401002.6 ± 0.6e ≤0.8e 7/10f 12/12e
dk/Sing + alum1,2808,0003201,600≤1.2e ≤0.8e 8/8e 12/12e
Alum102510256.3 ± 0.92.5 ± 1.00/70/10
  • a Serum samples pooled from 10 mice per group were used.

  • b Mean virus titers and protection from infection were determined on day 6 p.i. Titers represent means ± SD of 7 to 10 mice per group.

  • c Mice were monitored for 14 days after challenge. Mice in the alum-vaccinated group died on day 6 or 7.

  • d Mice were vaccinated with two doses of 10 μg of formalin-inactivated dk/Sing vaccine and challenged 4 months later with 50 LD50 of HK/483 virus.

  • e P < 0.001 compared with alum-vaccinated group.

  • f P < 0.01 compared with alum-vaccinated group.