Earlier this month, results from a two-year clinical trial showed that a new vaccine for tuberculosis is not as effective as researchers had hoped. Previous clinical trials proved the vaccine to be fairly effective in adults, but the most recent trial showed that it does not provide significant protection for infants.
The news was a major blow to modern medicine, which has been seeking a more effective TB vaccine for decades. The latest trial involved the first new vaccine to reach the human-trial stage since 1921.
Tuberculosis, or TB, is responsible for more than 1.4 million deaths each year worldwide, making it the second-most deadly infectious disease in the world after AIDS.
Now most prevalent in impoverished countries, TB is spread through airborne particles that carry the tuberculosis bacterium, Mycobacterium tuberculosis, into the lungs. If the bacteria aren’t suppressed by a person’s immune system, the disease can travel into other parts of the body, affecting almost any kind of tissue or organ. The condition is most often characterized by severe coughing, chest pain, coughing up blood and fatigue.
“With the increased awareness of global health issues and with some philanthropic efforts and funding, there has been a renewed effort at developing new vaccines and medications for tuberculosis,” said William Stauffer, M.D., associate professor of infectious diseases within the University of Minnesota Medical School. “Until recently, the drugs used to treat clinical tuberculosis were the same suboptimal drugs we have used for the last 50 years.”
Though the condition was first reported around 1850, it wasn’t until 1921 that researchers created an effective TB vaccine. While that vaccine, called Bacille Calmette-Guerin (BCG), is still being used today, its effectiveness has become limited after decades of crafting the vaccine around subcultures of the original bacterial strain. Researchers around the world are now trying to come up with a vaccine that produces better results.
The most recent clinical trial involved a new vaccine, MVA85A, developed at the University of Oxford. The trial was conducted among infants in South Africa who had already received the BCG vaccine. The nearly 2,800 children in the study were divided into two groups — one received MVA85A and one was given a placebo. Though the new vaccine had done well in adult trials, it was found that the drug was only 17% effective in preventing TB in the young children.
According to Stauffer, this isn’t the end of the road for MVA85A. Researchers hope the drug could benefit immunosuppressed adults, such as patients with AIDS. TB is especially dangerous in countries with high rates of AIDS because people with immune deficiencies aren’t normally able to fight the disease on their own and often don’t have the resources to get treatment. Furthermore, these patients can’t receive the BCG vaccine, meaning there is currently no vaccine for this patient population.
Fortunately, a dozen alternative TB vaccines are also being tested now which will hopefully bring in better results in the next few years. And that’s important, because with almost a third of all people carrying a latent form of the infection, tuberculosis is a health concern that needs to be put in a global spotlight as researcher continue to work toward an effective vaccine.