Two new vaccine candidates have shown promise in preventing TB infections, results of new clinical trials show. In a prevention-of-infection Phase II trial conducted in South Africa, re-vaccination with the Bacille Calmette-Guerin (BCG) vaccine significantly reduced sustained TB infections in adolescents. BCG is the world's only commercially available TB vaccine, and prevents some form of TB, but not pulmonary TB.
Another vaccine candidate, an experimental one—H4:IC31—also reduced sustained infections, although not at “statistically significant” levels. However, the trend observed for H4:IC31 is the first time a subunit vaccine (vaccines that use only one part of the disease-causing virus) has shown any indication of protecting against TB infection or disease in humans.
The announcement of the “encouraging” results from the “innovative clinical trials” was made on Monday by Aeras, a nonprofit organisation dedicated to developing vaccines against tuberculosis (TB). The study evaluated H4:IC31 vaccination and BCG re-vaccination for "safety, immunogenicity and the ability to prevent initial and sustained TB infections" among healthy adolescents in the Western Cape Province of South Africa. H4:IC31 is an investigative sub-unit vaccine candidate that is being jointly developed by Aeras and Sanofi Pasteur, the vaccines business of Sanofi, and the Statens Serum Institut.
The clinical trial was conducted at SATVI and at the Emavundleni Research Centre (part of the Desmond Tutu HIV Centre in the University of Cape Town, Africa). It was funded by Sanofi Pasteur, the United Kingdom’s Department for International Development, The Bill & Melinda Gates Foundation and Aeras.
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Over the past decade, more than a dozen new TB vaccine candidates have been tested in human clinical trials around the world..
Mark Hatherill, MD, director of the South African Tuberculosis Vaccine Initiative (SATVI) at the University of Cape Town, and the study’s principal investigator, said, “We are pleased to have performed the first-known randomised, placebo-controlled prevention-of-infection trial for TB and to have demonstrated that vaccination has the potential to reduce the rate of sustained TB infection in a high-transmission setting.”
While neither vaccine has proved to be “statistically significant” in preventing an initial TB infection, Hatherill insisted that the signals were extremely encouraging. “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.” Aeras would be presenting the detailed results of the study at the 5th Global Forum for TB Vaccines that starts on February 20 in the capital.
According to the World Health Organisation (WHO), about one-third of the world's population has "latent TB infection". This means that people have been infected by TB bacteria but are not yet ill with the disease, and cannot transmit the disease. People infected with TB bacteria have a 10 per cent lifetime risk of falling ill with TB. Those ill with TB can infect 10–15 other people through close contact over the course of a year.
India has the highest burden of TB in the world, and the government is targeting to eliminate the disease by 2025.