Farm‑based comparison of immunogenicity and safety of two live Hitchner B1 Newcastle disease virus vaccines in broilers: PayaVax® ND‑B1 versus a commercial counterpart

Newcastle disease (ND) is a major economic threat to poultry, necessitating effective vaccination under commercial conditions. This large‑scale farm study compared the immunogenicity, safety, and clinical outcomes of a locally produced live Hitchner B1 vaccine (PayaVax® ND‑B1) with a commercial NDV B1 vaccine in 20,000 broilers. Birds were allocated into three groups: PayaVax® ND‑B1, Commercial B1, and a Control group. Growth performance, humoral immunity (HI), vaccine virus persistence (RT‑PCR), and respiratory histopathology were evaluated. Both vaccinated groups showed comparable antibody kinetics, with significantly higher HI titres than the Control group at days 28 (p < 0.05) and 42 (p < 0.0001), demonstrating that day‑1 B1 priming provides sustained enhancement of systemic humoral immunity. Growth performance and mortality remained within commercial standards with no significant differences between groups (p > 0.05). RT‑PCR detected NDV RNA only transiently in oropharyngeal swabs at day 14. Histopathological evaluation revealed no significant differences between groups (p > 0.05), confirming excellent local safety. In conclusion, PayaVax® ND‑B1 demonstrated immunogenicity, replication kinetics, and safety profiles comparable to the commercial B1 vaccine, supporting its use as a reliable alternative for routine ND control in commercial broilers.