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Futher numerical analyses of the badger vaccine study (BVS) - SE3254

Description
The incidence of bovine tuberculosis (bTB) has continued to rise in British cattle herds with an increase in confirmed cases of over 200% between 1998 and 2007, at considerable economic cost to both farmers and Government. Whilst transmission of Mycobacterium bovis, (the causative agent of bTB), amongst cattle is an important factor in the spread of disease, the Eurasian badger (Meles meles) represents a significant wildlife reservoir of M. bovis infection. Following last year's Ministerial statement that badgers would not be culled as part of control measures for bovine TB in England (http://www.defra.gov.uk/corporate/ministers/statements/hb080707.htm), vaccinating badgers against bTB is seen as a vital component in the overall strategy for controlling bTB in cattle in England.

Results from the Badger Vaccine Study (BVS, Defra contract CBO115) and ongoing Vaccine Efficacy Studies are pivotal to obtaining a licensed vaccine for wider use in badgers. The application to obtain a Marketing Authorisation for the injection of BCG into badgers will include safety data from the BVS and efficacy data from experimental challenge of BCG administered to captive badgers. A secondary objective of the BVS is to assess vaccine efficacy in the field using a basic generalised linear model to compare the incidence of positive test results in vaccinated and control groups. This pragmatic approach was considered the most appropriate for the purposes of applying for a Marketing Authorisation (MA), but fuller analyses may provide additional valuable information on individual and population level responses to vaccination.

The primary analysis scheduled under the BVS is due to be completed by March 2010. Upon completion of the BVS there will be a requirement to fully exploit the data collected over the four years of the study (2006-2009) to gather as much information as possible on the field effectiveness of the vaccine and the wider biological and ecological effects of vaccination. It is important to maximise returns on investment in the BVS by carrying out a thorough exploration and analysis of the enitire data set once it is available.

This proposal describes an extensive analysis of the BVS data over and above that which is currently funded under contract CB0115. We propose to employ additional, in-depth statistical methods to fully explore:

1. evidence of vaccine efficacy in wild badgers
2. evidence for increased survival of vaccinated badgers incl. the effect of vaccinating animals with pre-existing infection
3. evidence for a "herd immunity" effect
4. the effects of vaccination on demographic processes and on badger behaviour

Using a more flexible statistical approach will enable us to account for the disparity of infection risk associated with individuals recruited into the study at different time points as well as exploring the effects of a range of covariates that might influence vaccine efficacy. We will also provide estimates of survival, an assessment of 'herd immunity' and a detailed synthesis of the wider effects of vaccinating wild badgers. These analyses will follow the primary analysis being conducted as part of the BVS, and together with other sources of evidence will help inform decisions relating to future potential use of the BVS area and it's badger population. More importantly, this information will be critical to decisions on how best to use BCG in badgers to control bTB in cattle.
Project Documents
• FRP - Final Report : Final report SE3254   (961k)
• ANX - Annex : Modellling Annex SE3254   (108k)
Time-Scale and Cost
From: 2010

To: 2011

Cost: £142,891
Contractor / Funded Organisations
Central Science Laboratory
Keywords
Animal Diseases              
Animal Health              
Plants and Animals              
Tuberculosis              
Vaccines              
Fields of Study
Animal Health