With the recent announcement that trials for a vaccine for cattle against TB are to get underway, Hannah Noble caught up with UK Chief Veterinary Officer Dr Christine Middlemiss to gain an understanding of the steps which must still be taken.
A new weapon in the armoury in the fight against bovine TB could be on the horizon for British farmers, says UK Chief Veterinary Officer Dr Christine Middlemiss.
Although the prospect of a commercially-available vaccine is ‘exciting’ it will not be a silver bullet to TB eradication, she adds. Rather it will be a new tool in the box to help with the prevention of new infections and one which will take several years to come to fruition.
She says: “Finding cattle which are infected, testing them and taking them out of the system, as well as managing risk-based trading and biosecurity, will still be important aspects of the TB eradication plan.”
The task of trialling and certifying a new vaccine is an onerous one and Dr Middlemiss says she anticipates trials to run until 2024 before the data gathered is assessed by the Veterinary Medicines Directorate (VMD) in terms of its safety and efficacy.
The VMD is the UK’s veterinary medicines regulator responsible for assessing applications for marketing new veterinary medicines against legal requirements. VMD policy and technical specialists independently assess trial findings to ensure new drugs are authorised appropriately.
Dr Middlemiss says: “We hope very much the vaccine will become available but we do not want to pre-judge. We hope for the right data and its marketing authorisation but it is an independent process for VMD to do.
“Scientific procedures are not always necessarily straightforward, but it is most important we carry out a robust and effective study to get the right data to be reviewed – that is a priority.”
Trials of the vaccine are expected to get started in England and Wales within the next year.
One of the drawbacks of vaccination for infectious diseases has always been the ability to differentiate infected and vaccinated animals (DIVA). This is because both infection with the disease and vaccination prompt a similar immune response within the animal and, therefore, requires a highly specific DIVA test to be developed to diagnose infection.
Dr Middlemiss says although the vaccine to be trialled is based on the one which has been used to protect humans against TB since the 1920s, each species must have its own separate trials. Furthermore, she says, establishing an effective DIVA test is the aspect which has taken significant time to develop.
“The DIVA test has been refined as we have gone along to make it more specific. Testing the DIVA and its safety and efficacy is as important as the vaccine.”
The advent of a DIVA test means England and Wales will still be able to work towards the target of TB eradication alongside vaccination.
Dr Middlemiss says: “We very much want to join Scotland in being recognised as officially TB-free. Not just because of the reputational global impact, but because of the positive benefits that has for farmers in not having animals taken out of the system before their productive life is finished and managing the huge stress and anxiety burden we recognise TB is.”
Although Dr Middlemiss is at this time unable to specify exactly how the introduction of a vaccine could be rolled out, she says areas across England and Wales are faced with differing levels of infection so it is important an epidemiologically robust approach is taken to provide the optimum benefit from a disease and farm business perspective.
Whether the responsibility for administration of the vaccine would lie with vets or farmers is uncertain, but Dr Middlemiss says it will rely heavily on the data which is gathered during the trials and the marketing authorisations, if and when they are awarded. But she says administration will be carried out in the most effective way from a scientific perspective, as well as from a logistics perspective.
The responsibility of shouldering the cost of the vaccine is as yet undecided. Dr Middlemiss says the UK will be in a different parliamentary period by the time any authorisation would be granted, meaning the cost would be a policy decision for the Government in office at that time.
If the vaccine is to gain the appropriate authorisation, combined with an effective authorised DIVA test, it will be the first of its kind and Dr Middlemiss says it could be of benefit around the world.
“I can see we will not only be using it towards our eradication strategy but there are many countries, particularly developing countries, around the world that have big TB problems which impacts on their herd’s productivity.
"In some countries it impacts on people’s health too as a zoonotic disease in places where there is little access to milk pasteurisation. So we can see on a global basis that a vaccine will be quite an impactful tool.”
Should the vaccination come to the market, Dr Middlemiss says until England and Wales have the same status as Scotland pre- and post-movement testing would continue with the aim of preventing the further spread of infection and ultimately gaining UK-wide TB-free status.
She says: “We are looking to evolve our badger control in-line with the eradication programme and they are not directly dependent on each other but as we progress taking an epidemiologically-based approach on what infection levels around the country are, we will continue to progress evolution of wildlife control and our cattle controls.
“Vaccination is potentially an effective tool to reduce infection in cattle, but ultimately we do not want to have the pathogen out there which can infect cattle.”