Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: November 4, 2008
Publication Date: November 4, 2008
Citation: Swayne, D.E. 2008. The science behind avian influenza vaccine use as a control tool [abstract]. In: Abstracts of the BARD Workshop on the Evaluation of Novel Technologies for Reducing Environmental Spread and Efficient Eradication Strategies for High Pathogenicity Avian Influenza, November 2-6, 2008, Anatalyo, Turkey. p. 34. Technical Abstract: Prior to 2003, vaccines against avian influenza (AI) had limited, individual country or regional use in poultry. In late 2003, H5N1 high pathogenicity (HP) AI spread from China to multiple Southeast Asian countries, and to Europe during 2005 and Africa during 2006, challenging governments and all poultry production sectors to seek alternatives to stamping-out programs to control and eradicate AI. AI vaccines have emerged as a new tool for use in comprehensive high pathogenicity (HP) AI control strategies. Historically, AI vaccines have been based on field outbreak strains of the same hemagglutinin subtype grown in embryonating chicken eggs, chemically inactivated, emulsified and administered by parenteral injection. Protection has been primarily the result of an antibody response to the hemagglutinin (HA) protein and is specific to an HA subtype. Recently fowl poxvirus and avian paramyxovirus type 1 (ND) virus vectored vaccines with AI H5 gene inserts have been developed, licensed and used. Two main critical aspects affect vaccine success in an AI control program: 1) vaccine efficacy, and 2) vaccination effectiveness. Vaccine efficacy encompasses the safety and purity of the vaccine, having sufficient antigenic content to produce robust protective immune response, and a sufficiently close genetic match of the hemagglutinin to protect from minor genetic drift. Vaccination effectiveness involved all aspects of application of vaccines from storage to administration. When properly applied, high quality AI vaccines will protect poultry by increasing resistance to infection, preventing illness and mortality, reduce the number of infected birds, and if infected, greatly reduce the amount and time that virus is shed from respiratory and alimentary systems. This translates into reduction in environmental contamination or viral load by AI virus and thus reduced transmission to birds and humans. Vaccines can be used as part of an emergency control program during an active outbreak or can be used routinely if AI is endemic in the region. An archive vaccine bank for H5 and H7 AI can be of value great value in emergency program. However, vaccination alone will not eradicate AI. Vaccination should only be used as one tool in a comprehensive control program that includes enhanced biosecurity, increased surveillance, education of poultry workers, and elimination of infected poultry.