Since autumn 2005 Viet Nam has been practicing mass vaccination of poultry, twice yearly in October and April, to control epidemic Highly Pathogenic Avian Influenza (HPAI) H5N1 with some considerable empirical evidence of success (Table 1). However, it has been recognized that this control strategy is not sustainable over the whole country in the long term. Therefore, an alternative or more likely many alternative control strategies will have to be devised as Viet Nam moves from initial emergency measures to a period of consolidation and ultimately on to the stated aim of control/eradication beyond 2010 (Green Book). The objective of this project is to provide field data by testing a number of alternative strategies including differing vaccination strategies and the complimentary strategy of improved surveillance.
This project will look at alternative vaccination strategies in both high and low risk provinces for HPAI H5N1 (High risk are Nam Dinh, Ninh Binh, Soc Trang and Hau Giang provinces; low risk is Quang Binh province). In a high risk province in the Red River Delta and a second province in the Mekong Delta, the alternative vaccination strategy being proposed is an age based vaccination strategy targeted at small commercial poultry units as this is where the majority of HPAI H5N1 outbreaks occur. The rationale for this is that improved immunity in smaller commercial farms will provide protection for the smaller backyard poultry. However, as this is a transitional strategy there will still be one round of vaccination (instead of the national twice-yearly campaigns) in backyard poultry units in November 2008 to protect them over the high risk time leading up to the Lunar New Year Festival 2009 (Tet). With the Government’s agreement mass vaccination of backyard flocks could cease in late 2009 in the V2 areas. It is a transition towards the Government being less directly involved in vaccine delivery to small commercial and backyard poultry; transferring the financial burden of vaccination increasingly towards the farmer. The vaccine chosen for these trials is the Chinese Harbin inactivated oil adjuvant H5N1 vaccine as this is currently both the most immunogenic vaccine in chickens and ducks and the cheapest. In a selected low risk province which has decided not to have compulsory vaccination for chickens or ducks, an observation study will be carried out looking at the role of increased surveillance.
To complement these vaccination intervention studies, the following components will be carried out: a socioeconomic study to examine the cost as well as farmer actions and attitudes towards different strategies; in-depth epidemiological studies at outbreaks of HPAI H5N1 countrywide during the project to identify and evaluate risk factors; work on refining the current mathematical models to increase understanding of the dynamics and economics of vaccination; historical and prospective policy analysis to give a better understanding of the evolution of decisions and decision-making processes that led to the effective HPAI H5N1 vaccination campaigns in Viet Nam which started in 2005. In all the study areas, collaboration with the human health sector including surveillance for human cases or infection and joint outbreak investigation, will be ensured by the Ministry of Health (MoH).
The sum total of these studies should allow animal health policy-makers to make better informed choices on future HPAI control strategies.