Cape Town vaccine trial cuts TB infections in half
The success of the clinical trial of an old vaccine even shocked the scientists conducting it
What if you could cut TB rates almost in half with one simple step? You can, according to new research in Cape Town.
It found that giving a vaccine jab to adolescents who had one as babies cut their chances of a sustained infection by 45%.
The success of the clinical trial of an additional dose of the Bacille Calmette-Guerin (BCG) vaccine even shocked the scientists conducting it.
“The robustness of the BCG results to help clear or control an infection were surprising,” said Ann Ginsberg, chief medical officer for Aeras, a non-profit organisation working to develop new TB vaccines.The trial was carried out at the South African Tuberculosis Vaccine Initiative (SATVI) and the Emavundleni Research Centre in Crossroads, part of the Desmond Tutu HIV Centre.
Researchers randomly chose 990 HIV-negative, healthy adolescents aged 12-17 — who had been vaccinated with BCG as infants — to receive one of three jabs: a placebo, an experimental vaccine or BCG, which has been in use for close to a century.
The trial, which began in 2014, measured the rate at which the individuals tested positive for TB infection at six-month intervals over a period of two years.The World Health Organisation says about a third of the world’s population have latent TB infection, which means they carry the bacteria but are not ill and cannot transmit the disease.
According to the findings, the vaccine efficacy for preventing a sustained infection was about 45%, while the experimental vaccine chalked up a 30% efficacy rate.
Mark Hatherill, director of the SATVI at the University of Cape Town and the study's principal investigator, said it showed BCG vaccination had the potential to reduce the rate of sustained TB infection in a high-transmission setting.BCG was effective in preventing sustained infections, as participants who initially tested positive for TB infection were more likely to have cleared or controlled the infection within six months, he said.
“We believe the results from this novel trial design will provide significant scientific benefit to the field in understanding TB infection, and based on this positive signal we look forward to testing the potential of such vaccines to prevent TB disease among uninfected adolescents in a larger, more traditional prevention-of-disease clinical trial,” he said.
Ginsberg said the study “provided valuable, modern data on a very old vaccine – data that the field can use to potentially optimise BCG vaccination strategies and create new, more effective TB vaccines.’’Linda-Gail Bekker, a lead investigator for the trial and chief operating officer at the Desmond Tutu HIV Foundation, thanked the study participants and their families.
“We believe the results are important and warrant ... a re-evaluation of BCG revaccination as a potential strategy to prevent TB in high-incidence countries. An effective TB vaccine remains an urgent global goal,” she said.
The results of the Cape Town trial were presented at the fifth Global Forum on TB Vaccines in New Delhi, India, in February.