At the first day of the International Symposium "Research and development of new tuberculosis vaccines" in Zaragoza, Spain, researchers reinforced the need for new vaccines against tuberculosis (TB), pointing out that TB is a continuously growing health problem and the only currently available vaccine, BCG, has limited efficacy in adults and safety issues in HIV-infected newborns.
"I don't need to remind people here of the state of the problem," said Dr. Ann Rawkins of the Center for Emergency Preparedness and Response of the Health Protection Agency, United Kingdom, referring to the 2 million TB-deaths and 9 million new TB cases worldwide per year. "The international goal of elimination of the [TB] disease by 2050 cannot be reached unless we get new diagnostic tests, new drugs and new vaccines. A large number of new vaccine candidates are currently at various stages of development."
The BCG vaccine is widely used and given to newborns worldwide. It protects against severe forms of childhood TB. But BCG has little to no efficacy in preventing pulmonary TB in adults, the most common and most infectious form of TB worldwide. Furthermore, because of safety issues in HIV-infected newborns, the World Health Organization (WHO) advises not to use BCG in babies known to be infected with HIV.
Research into new TB vaccines either aims to improve the BCG vaccine, to boost the immunity BCG gives, or to replace it. Professor of Immunology Hazel Dockrell of the London School of Hygiene and Tropical Medicine stressed the need to know exactly what the BCG vaccine is doing. "BCG has been around for a very long time, it was first given to a child in 1921, it is surprising we don't know more about it," she said, elaborating on various questions surrounding BCG.
"We need to understand what sort of immunity BCG gives and what features of BCG should be improved."
Research done by Dockrell and colleagues shows that both young adults and infants in the United Kingdom and Malawi give a different sort of immune response to BCG vaccination. "That matters because many new vaccines now in development are boosting vaccines, aiming to improve BCG. But will they work better than BCG in areas where BCG itself doesn't induce good protection?"
Professor Paul-Henri Lambert from the University of Geneva stressed the importance of safety issues for new TB vaccines. "Rare adverse events can kill newly developed vaccines. A theoretical risk of safety issues has often hampered the development of a new vaccine. And unjustified allegations can lead to limiting use of a good vaccine," he said.
Prof Douglas Young, Fleming Professor of Medical Microbiology at the Imperial College in London highlighted the importance of more diversity in TB vaccine research. Most vaccines currently in development focus on boosting the body's natural immune response. "But it might as well be that the vaccines we're making at the moment are exactly the vaccines TB wants us to make," Young warned.
"TB might be perfectly happy with the way the natural immune response works, getting enough opportunities to transmit," he said, elaborating on the global diversity of TB strains and how these strains orchestrate the body's immune reaction. While current research is centered around cell-mediated immunity, "there is a landscape of diversity which is not yet exploited," Young said, encouraging his fellow scientist not to neglect the immense variety of immune response.
The two-day symposium on new TB vaccines is organized by the University of Zaragoza, Spain, the foundation Ramon Areces and TuBerculosis Vaccine Initiative (TBVI).
