A freeze-dried temperature-stable tuberculosis vaccine that lasts for months in storage is safe and effective in healthy adults, according to the results of a new trial.
The trial is the first of any TB vaccine candidate of its type in a temperature-stable (thermostable) form, investigators said. The researchers aimed to find whether a single-vial containing the vaccine and an immune-boosting adjuvant would be as effective at inducing an immune response as a regimen in which a non-thermostable version of the vaccine is combined with the adjuvant prior to injection.
Long-term stability in storage
Thermostable vaccines may be useful in settings where maintaining cold or frozen vaccines for long periods can be costly and difficult, according to the National Institutes of Health, which supported the trial. The trial vaccine is a recombinant subunit vaccine (containing purified parts of the pathogen). The adjuvant-containing version is thermostable for three months at 37 °C, which is significantly longer than currently licensed thermostable vaccines, which typically last only days or a few weeks, the researchers said.
The vaccine, developed at the Access to Advanced Health Institute in Seattle, is made from four proteins of Mycobacterium tuberculosis bacteria plus an immune-stimulating adjuvant, NIH reported in a release. “The freeze-dried formulation does not require refrigeration and is mixed with sterile water just prior to injection,” it said.
Safe and effective
Both types of vaccine presentation — thermostable and nonthermostable — were safe and well-tolerated in the small cohorts totalling 45 participants, according to the researchers, from the Saint Louis University Center for Vaccine Development. But the thermostable vaccine appeared to have some advantages.
“Recipients of the single-vialled thermostable vaccine had robust T-cell responses and produced higher levels of antibodies in the blood than those receiving the non-thermostable two-vial presentation,” NIH reported.
Although it remains to be seen whether the heightened immune responses will translate to improved vaccine efficacy, the researchers concluded that, “adjuvant-containing vaccines can be formulated in a freeze-dried single-vial presentation without detrimentally impacting clinical immunogenicity or safety characteristics.”
The study was published in Nature Communications.
