New typhoid vaccine offers hope of protection for children

A new typhoid vaccine for both adults and children has been proven by Oxford researchers to be safe and effective in preventing the disease.

Typhoid is caused by the bacterium Salmonella Typhi, and is responsible for around 20 million new infections and 200,000 deaths each year, mainly in South and South-East Asia and Africa.

The disease is associated with inadequate sanitation and contaminated drinking water, and common symptoms include fever, stomach pain, headache and constipation or diarrhea.
Children are especially susceptible, but the currently licensed vaccines do not confer lasting immunity in children, and/or come in inappropriate formats.

A study published in The Lancet is the first clinical trial to show that immunisation with a new typhoid conjugate vaccine (TCV) is safe, well tolerated and will have significant impact on disease incidence in typhoid-endemic areas that introduce the vaccine.

The trial was led by Professor of Paediatric Infection and Immunity at the University of Oxford, and Director of the Oxford Vaccine Group, Professor Andrew Pollard and funded by a grant from the Bill & Melinda Gates Foundation.

‘This new vaccine could be a real game changer in tackling a disease that disproportionately affects both poor people and children,’ Prof Pollard said. ‘For the first time, we will be able to offer protection to children under two years of age, which will enable us to stem the tide of the disease in the countries where it claims the most lives.

‘If we are going to make serious headway in tackling typhoid, we need to dramatically reduce the number of people suffering from and carrying the disease globally, which will in turn lead to fewer people being at risk of encountering the infection.

‘This is a disease that only affects humans, and I believe that it will be possible for us to eradicate one day. However, we’re currently losing ground as overuse of antibiotics is leading to the emergence of new resistant strains, which are spreading rapidly.’

The researchers tested the vaccine at Oxford University using a controlled human infection model, which involved asking around 100 participants, many of whom were university students, to consume a drink containing the bacteria. Human infection models have been used for hundreds of years to test vaccines, and are particularly useful in studying diseases for which no suitable animal model exists.

Dr Charlie Weller, Head of Vaccines at Wellcome, said: ‘Human infection models have been used in research in some form for hundreds of years. They enable researchers to gather rich information about how a disease behaves in the body in a way that is not always possible from conducting animal studies.

‘As this study shows, they can also give us an indication that a vaccine is safe and effective far more quickly than would be possible through large-scale population trials.’

Dr Anita Zaidi, Director of the Enteric and Diarrheal Diseases team at the Bill & Melinda Gates Foundation, said: ‘Many people think typhoid is a disease of the past, yet it still sickens millions of people annually, particularly children. This is a stain on global health progress when advances have been made against many other diseases.

‘These new results from Oxford University’s typhoid vaccine study provide exciting evidence that we may soon be able to protect children against typhoid with an effective vaccine. This vaccine would be a critical tool, alongside water and sanitation efforts, to help make real headway against this deadly disease and consign it to the history books where it belongs.’

Dr Krishna Ella, Chairman & Managing Director of Bharat Biotech, while commenting on the Lancet publication stated that the Company is pleased that the vaccine has been found to be extremely effective in the human challenge studies: ‘The results of this study endorse more than 10 years of R&D efforts to develop this vaccine and various clinical trials that have been carried out over the past eight years.’

The full paper, ‘Efficacy and immunogenicity of a Vi-tetanus toxoid conjugate vaccine in the prevention of typhoid fever using a controlled human infection model of Salmonella Typhi: a phase IIb observer-participant-blinded, randomised controlled trial,’ can be read in The Lancet.