A novel vaccine against deadly tuberculosis (TB) has shown to be safe and effective, according to the results of Phase 1 clinical trial.

Currently, Bacille Calmette-Guerin (BCG) is the most widely administered vaccine against TB across the globe. Nearly 100 years old, it is the only vaccine ever administered to treat TB, which afflicts more than 10 million people each year.

In the trial, US scientists tested a vaccine formulation that was freeze-dried. It was stable at temperatures of almost 37 Celsius for three months -- an advance that could help in areas where maintaining cold or frozen vaccines for long periods can be costly and difficult.

Developed by a team of scientists at the Access to Advanced Health Institute (formerly the Infectious Disease Research Institute) in Seattle, US, the experimental vaccine, ID93+GLA-SE, does not require refrigeration and is mixed with sterile water just prior to injection.

The thermostable vaccine was tested in 45 healthy adults who were then monitored for six months after receiving two shots given 56 days apart. Of these, 22 participants were given a different vaccine formula that isn't stable at higher temperatures.

The results, published in Nature Communications, found that the experimental TB vaccine was safe and stimulated both antibodies and responses from the cellular arm of the immune system.

While both vaccine presentations were safe and well-tolerated. Those who got the thermostable vaccine showed robust T-cell responses and produced higher levels of antibodies in the blood than those receiving the non-thermostable vaccine, according to the team from Saint Louis University Center for Vaccine Development, who led the trial.

They also acknowledged some limitations in the trial such as no established correlates of protection defining what immune responses are required for vaccine-induced protection from TB disease.

As a result, it is not possible to say whether the enhanced immune responses seen in the thermostable vaccine formulation would translate to improved protective vaccine efficacy.

Nevertheless, they said, the results of this trial demonstrate "proof-of-concept that adjuvant-containing vaccines can be formulated in a freeze-dried single-vial presentation without detrimentally impacting clinical immunogenicity or safety characteristics."