Humoral antibody responses to different H5N1 and H5N2 vaccination regimes: implications for the development of autogenously based vaccines.

Whereas H5N1 vaccine and several H5N2 vaccines are commercially available and are used to control H5N1 outbreaks in some endemic countries, infections hit many vaccinated flocks. The following study was conducted to compare the efficacy of such vaccines and to assess their potential induction of antibodies against the haemagglutinin of local H5N1 isolate after single vaccination. The possible beneficiary effect of booster dose at different intervals was screened for both H5N1 vaccine as well as a selected H5N2 candidate. Differences in the serological immune response among native and cross breeds were also screened. No significant variations were detected between available commercial H5N1 and H5N2 vaccines after single vaccination. Two vaccination shots using H5N1 but not H5N2 vaccine were found to be superior to a single vaccination scheme, where chicks developed more conceivable antibody titers than in single vaccination program. There was considerable variation among chicken lines in the immune response to H5N1 vaccine: native breeds possessed the highest antibody titers as compared to other breeds.