Advances and challenges in avian influenza vaccines: From conventional approaches to next-generation strategies.

Abstract

Avian influenza viruses (AIVs), particularly highly pathogenic H5 and H7 viruses, pose major threats to poultry production, food security, international trade, and public health. Vaccination is an important component of AIV control; however, antigenic evolution, incomplete reduction of viral shedding, and challenges associated with large-scale poultry vaccination limit its effectiveness. In addition to conventional vaccines, recombinant and nucleic-acid platforms have emerged in response to rapidly evolving AIVs. Relevant literature on inactivated, live attenuated, recombinant subunit, viral-vector, DNA, mRNA, and virus-like particle vaccines was evaluated. Immune responses, protection, antigenic breadth, viral shedding, delivery, manufacturing, field applicability, and regulatory considerations were analyzed. Inactivated vaccines are well-established, safe, scalable, and cost-effective but provide limited cellular and mucosal immunity and require antigenic matching. Live attenuated vaccines can induce broader immunity and facilitate mass vaccination but present biosafety, reassortment, and genetic-stability concerns. Next-generation platforms provide greater antigenic flexibility and opportunities for broader protection. Viral-vector vaccines can induce both humoral and cellular immunity, while recombinant subunit, DNA, mRNA, and VLP vaccines offer rapid redesign and multivalent formulations. However, challenges remain regarding delivery, stability, manufacturing, durability, and field validation. No single platform currently meets all requirements for sustainable AIV control. Future strategies should emphasize conserved or mosaic antigens, durable and mucosal immunity, rapid vaccine updating, DIVA compatibility, and scalable delivery. Combining conventional and emerging platforms through prime-boost or multi-platform strategies may provide more flexible and effective control.