Infectious Diseases 2025

Infectious Diseases 2025

The AHAW & ECDC opinion on avian influenza vaccination of animals

29 January, 2025

The Scientific Opinion of the EFSA Panel on Animal Health and Animal Welfare (AHAW) and the European Centre for Disease Prevention and Control (ECDC) regarding the Vaccination of Animals Against Avian Influenza.
Vaccination against Highly Pathogenic Avian Influenza (HPAI) represents a valuable tool for preventing and controlling the spread of HPAI when integrated into a comprehensive strategy for disease prevention and management. Various vaccines targeting Highly Pathogenic Avian Influenza Viruses (HPAIVs) are currently available. Additionally, experimental efforts are underway in the United States to develop an avian influenza vaccine intended for use in cattle. The primary points that underscore the efficacy of vaccination for avian influenza in poultry are as follows:
-Reduction in Virus Circulation: When effectively implemented, vaccination can significantly diminish the circulation of the avian influenza virus within poultry populations. This reduction contributes to lowering the overall viral load in the environment, thereby decreasing the likelihood of outbreaks and subsequent transmission.
-Decrease in Human Exposure: By controlling HPAI in poultry populations, vaccination can indirectly mitigate the risk of human exposure to the virus, a factor of particular concern for strains that have the potential to infect humans.
-Complementarity to Other Measures: Vaccination should not be viewed as a stand-alone solution; it must complement other existing measures in poultry and wild bird populations, such as biosecurity protocols, early detection systems, and surveillance. This integrated approach enhances the overall efficacy of prevention and control efforts.
-Prevention of Economic Losses and Welfare Impairment: Outbreaks of avian influenza can have devastating effects on the poultry industry, resulting in substantial economic losses attributable to culling and trade restrictions. Furthermore, the welfare of infected animals is compromised by the clinical manifestations of the infection and by the specific control and prevention measures implemented (e.g., the indoor confinement of outdoor-raised poultry during high-risk periods for virus introduction). Vaccination serves to mitigate these impacts by preventing extensive outbreaks.
When implementing vaccination against HPAI in poultry, various challenges and limitations must be taken into account, particularly:
Correlate of protection: The absence of a reliable immunity threshold that indicates protection, along with limited knowledge regarding the duration of protective immunity in vaccinated poultry, hinders the planning and execution of effective vaccination campaigns.
Antigenic matching: The efficacy of a vaccine is contingent upon its alignment with the circulating strains of the virus. Continuous surveillance is essential to monitor viral evolution and to ensure that vaccines maintain their effectiveness.
Risk of vaccine-induced mutants: Inadequate or improper vaccination can result in the emergence of vaccine-induced viral mutants that may exhibit increased virulence or resistance, thereby complicating eradication efforts. Moreover, potential vaccine escape mutants that may arise during vaccination need to be considered, with the risk of silent circulation being contingent upon the surveillance strategy employed in vaccinated populations.

In conclusion, vaccination against Avian Influenza represents a significant tool with the potential to diminish viral circulation, safeguard human health, and protect animal welfare as well as the poultry industry. Nevertheless, the success of such vaccination efforts is predicated upon proper implementation, ongoing surveillance, and integration with other preventive measures.

 

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