Title: Global assessment of avian influenza control strategies, especially the role of vaccine efficacy and vaccination effectiveness Authors
|Pavade, Gounalan -|
|Hamilton, Keith -|
Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: May 20, 2011
Publication Date: September 7, 2011
Citation: Swayne, D.E., Pavade, G., Hamilton, K. 2011. Global assessment of avian influenza control strategies, especially the role of vaccine efficacy and vaccination effectiveness [abstract]. Abstract of Bird Flu 2011 Conference, Oxford, United Kingdom, 7-9 September 2011. CD-ROM. Technical Abstract: OFFLU is the joint World Organisation for Animal Health and Food and Agricultural Organization (OIE-FAO) global network of expertise on animal influenzas. OFFLU aims to reduce negative impacts of animal influenza viruses by promoting effective collaboration between animal health experts. OFFLU puts a strong emphasis on the importance of analyzing and sharing information, and biological material to identify and reduce health threats early. An OFFLU Global Avian Influenza Vaccine and Vaccination research project seeks to define the conditions where avian influenza (AI) vaccines can assist in control and eradication of H5N1 HPAI in Asia and Africa. Vaccines and vaccination have emerged during the past two decades as essential tools in AI control for poultry because they: increase resistance to infection, prevent illness and death; reduce virus replication and shed from respiratory and alimentary tracts; and reduce virus transmission to birds and mammals, including humans. However, as H5N1 viruses have become entrenched and outbreaks prolonged, field outbreaks have been reported in flocks that are well vaccinated with early classical H5 AI vaccines in Central America, China, Egypt and Indonesia. These failures can be the result of failure of the vaccines (i.e. vaccine efficacy) or failure in administration or immune response of the target species (i.e. vaccination effectiveness). Vaccine Efficacy: Low antigenic mass in H5 AI vaccines is less common a problem today as it was 10 years ago. The market place has demanded high potency vaccines and most manufacturers have provided such to stay in the market. However, in some regions antigenic drift of the field viruses has occurred such that older classic H5 vaccine seed strains have lost efficacy and continual evaluation of vaccine seed strains against field viruses is needed to maintain relevant protective vaccine seed strains. Vaccination Effectiveness: The most common cause of lack of protection in the field has been associated with a variety of application and related issues: attempting to vaccinate all poultry in the national herd; improper vaccination technique; trying to get field protection from a single vaccination; maternal and active immunity interference; immunosuppressive population; improper storage & handling of vaccines; administration of reduced vaccine dose; high environmental exposure to virus; farmer resistance to vaccination of domestic ducks; high population turnover rate in poultry; logistics problems with administration; and vaccination “burn-out.” Strategies to reach the village poultry and small commercial sector are essential for control and eradication of H5N1 AI, but require more knowledge on reservoirs, market chains and movement of poultry.