A new vaccine may help boost the efficacy of Bacille Calmette Guerin (BCG), currently the only tuberculosis (TB) vaccine available, offering new hopes for the global fight against the disease, Canadian researchers said Wednesday.

BCG, typically given in the first year of life, was developed in the 1920s and has been used worldwide. It is most effective in protecting children from the disease, but doesn't work very well in adults.

The new vaccine, based on a genetically modified cold virus, will not replace the old vaccine, but is designed to be given following initial BCG vaccination to boost the immunity triggered by BCG, researchers at McMaster University reported in the US journal Science Translational Medicine.

The researchers began the first human clinical trial in 2009 with 24 healthy volunteers, including 12 who were previously BCG- immunized, said Professor Zhou Xing, who led the study.

"The primary goal was to look at the safety of a single dose vaccine injection as well as its potency to engage the immune system," Xing said of the phase one clinical study.

The researchers found that injection triggered the right immune responses at a higher level in previously BCG-immunized individuals compared to non-BCG immunized individuals. In addition, no serious side effects were observed.

They established that the vaccine was safe, but Xing said that more clinical trials are needed to measure the vaccine's real potential.

Tuberculosis is second only to HIV/AIDS as the greatest killer worldwide due to a single infectious agent.

According to the World Health Organization, about one-third of the world's population has latent TB, which means people have been infected by TB bacteria but are not ill with disease and cannot transmit the disease. Every year, more than 8 million people are newly diagnosed with TB disease, and more than 1 million die.