Typhoid vaccine trial
19 February 2008
Responsible for around 200 000 deaths a year, typhoid fever is a major global health problem. A new vaccine developed with Wellcome Trust Technology Transfer funding has recently completed a phase II clinical trial, involving children aged between five and 14 in Vietnam. Encouragingly, the vaccine was both safe and elicited good immune responses in the vaccinated children.
The vaccine has been developed by Emergent Biosolutions Inc., a US-based vaccine and therapeutic company. It is a single-dose drinkable vaccine based on a live attenuated strain of Salmonella typhi, the bacterium that causes typhoid fever. The strain has two genes deleted, which abolishes its ability to cause disease. Early development of the vaccine was carried out by Reading-based company Microscience, which later became part of Emergent Biosolutions.
The latest trial was carried out in Vietnam, with support from Professor Jeremy Farrar and colleagues at the Wellcome Trust’s Major Overseas Programme. In a double-blind randomised control trial, 101 children received vaccine and 50 placebo. There were no serious adverse events in the treated group, who showed significantly higher antibody responses to bacterial antigens. Previous trials in the UK, USA and in adults in Vietnam have also shown that the vaccine is safe and immunogenic.
Although a phase II trial does not necessarily mean that the vaccine will protect against infection, the better-than-expected results boost confidence that the vaccine will be effective in the field and pave the way for larger phase III trials.