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[TALLIINN, ESTONIA] A vaccine for tuberculosis (TB) is unlikely to be ready until 2020, say scientists, who will revise the original target from 2015 in a report to be published next month.
A mid-term review of the ‘Global Plan to Stop TB 2006–2015’, which will be released after a meeting in Johannesburg, South Africa, next month (14-15 October) says that the 2015 goal was "optimistic", and predicts a bottleneck when it comes to carrying out later stage clinical trials.
The global plan was drawn up by the Stop TB Partnership and various stakeholders in 2006, and outlines a ‘big picture’ approach to tackling TB worldwide.
"It was unreasonable to claim to have the TB vaccine by 2015," said Michel Greco, chair of the Stop TB Partnership Working Group on New TB Vaccines. "If we have a valid vaccine produced by 2020 that will be a feat."
"2015 was too optimistic," Hassan Mahomed, clinical director of the South African TB Vaccine Initiative, told SciDev.Net, adding that "somewhere between 2016 and 2020 is a bit more realistic".
The scientists were speaking on the sidelines of the Second Global Forum on TB Vaccines, in Tallinn, Estonia this week (21-24 September), where they are putting together a detailed blueprint for the development of vaccines against the disease.
TB research has yielded 13 new vaccines, the most advanced of which will be ready for phase III trials in 2013. But scientists fear it will be difficult to find sites for these trials where the incidence of TB is high enough for the trials to be executed quickly.
Although TB is one of the most serious diseases in the world, with over nine million new cases each year and 1.8 million deaths, it is widely spread. This makes it hard to find a site where there are sufficient infections occurring for the protective effects of a vaccine to be easily detected.
Helen McShane, vaccinologist at Oxford University, United Kingdom, whose team is working on the most advanced vaccine candidate so far, told SciDev.Net that the highest incidence they have found at potential trial sites has been three per cent over a period of two years — the equivalent of only three people infected per 100 tested during a whole two-year trial.
Such an incidence would require a trial of about 40,000 people in order to adequately compare vaccinated and placebo groups.
McShane added that Phase III trials on TB vaccines, in their current form, may never be possible, and new approaches may be needed, such as modelling a trial instead.
A second impediment will be the lack of skilled capacity for conducting large-scale trials, and the lack of basic infrastructure, said Greco.
Keeping that capacity going between trials will be an even bigger challenge, he added.