Researchers have found that a nearly century-old vaccine is far more protective when injected into a vein rather than just under the skin. In tests on monkeys, scientists from the University of Pittsburgh’s medical school and the National Institute of Allergy and Infectious Diseases found that giving the tuberculosis vaccine intravenously provided 90 percent protection against the disease. Their research has been published in the journal Nature.
Tuberculosis kills about 1.7 million people a year, mostly in developing countries. The only tuberculosis vaccine, known as BCG for Bacille Calmette-Guérin after the French scientists who developed it, has been in use since 1921. It is made from a live, weakened form of the tuberculosis bacteria found in cattle and costs as little as $1 a dose.
While the vaccine is considered safe even for newborns, it is not very effective. It is often used to protect babies from one form of the disease, but it’s far less effective at protecting teens and adults against lung infections, the form that kills most TB victims. Scientists have been working for decades to make a powerful, long-lasting vaccine, but have thus far been unsuccessful.
In the Nature study, the researchers studied rhesus macaque monkeys, which react to TB infection much like people do. They tested a variety of ways to give the TB vaccine in six groups of monkeys. The first group got the standard dose by the normal skin injection route, a second got a much stronger dose, a third inhaled a vaccine-containing mist, a fourth got both injection and mist, and a fifth got the stronger dose by vein. The sixth, the control group, got no vaccine.
Six months after the vaccinations, the researchers delivered TB bacteria straight into the animals’ lungs and watched for infection. After six months, only nine of the 10 monkeys injected intravenously were well protected. The team found no trace of infection in six of the animals and counted very low levels of TB bacteria in the lungs of three.
The experts warned that rigorous safety testing would be needed before humans can be inoculated with the live bacteria into the bloodstream. They also still need to determine how long the protection lasts, since the monkeys were tested after only six months. Additional safety research is currently underway in animals, with researchers hoping to begin a first-step study in people in about 18 months.