Guidelines for the Administration of Nobilis Influenza H5 Vaccine as
Part of an Avian Influenza Control Strategy
J.H. Breytenbach
Intervet International b.v.
Wim de Körverstraat 35, 5830AA, Boxmeer, The Netherlands
1. Introduction
The current epizootic of highly pathogenic avian influenza (HPAI),
subtype H5N1, which started in Asia end 2003 and has since spread towards
the west into Russia, Turkey and Romania has raised international concern.
The ever increasing number of cases reported of people infected by this avian
influenza strain (Vietnam, Thailand and Indonesia), often with fatal
consequences, has raised concerns that this could trigger the start of a human
influenza pandemic, thus calling for prompt control measures.
Traditional control measures for HPAI have centred on stamping out,
which entails the large scale culling of infected flocks and contact flocks. This
policy has in the past proven effective however the high concentration of
poultry found in certain areas leads to the culling of millions of animals at
great expense.
Vaccination against AI has proven to be a successful additional control
measure implemented alongside controlled culling (Italy (H7N1 & H7N3),
Mexico (H5N2), Pakistan (H7N3), Hong Kong (H5N1), Vietnam (H5N1) and
Indonesia (H5N1)). In 2004 the FAO, OIE and WHO issued a joint statement
that called for a targeted strategy, including poultry vaccination, to help curb
AI in Asia.
The expected advantages of a vaccination policy are two fold. Firstly
vaccination reduces susceptibility to infection, a higher dose of virus is
necessary for establishing an infection in vaccinated birds. Secondly there is a
significant reduction in the amount of virus shed by infected birds, thus less
virus to contaminate the environment reducing the risk of spread to other avian
species and reducing the occupational risk faced by poultry workers.
(Reducing the incidence of human infections reduces the chance of the AI
strain mutating and the possible emergence of a new human influenza strain.)
Reducing the amount of avian virus allowed to multiply in poultry also
reduces the likelihood of mutations caused by random errors in transcription.
However, we hasten to caution that vaccination is not intended to replace
stamping out policies. The primary goal remains eradication of AI.
Vaccination, by increasing the infection threshold and decreasing virus
shedding, is a valuable aid in the eradication of AI infection when combined
with appropriate control measures.
The following document provides a guideline to the effective
implementation of an AI eradication policy using an inactivated influenza
vaccine, Nobilis Influenza H5.
2. Inactivated Avian Influenza Vaccines
Influenza virus is grown in embryonated eggs and is chemically
inactivated. Subsequently the inactivated viral antigen is formulated with an
oil emulsion adjuvant to enhance the immune response. Vaccine efficacy is
dependant on the vaccine antigen and field virus being of the same H type
(homologous haemagglutinin).
