Researchers have carried out a clinical trial of a freeze-dried, temperature-stable experimental tuberculosis vaccine that could one day be an alternative to the BCG vaccine, which has significant drawbacks.
At present, BCG is the only vaccine licensed against TB. BCG is a freeze-dried powder that must be stored under frozen conditions and can be “readily destroyed by sunlight,” according to a World Health Organization (WHO) manual (pdf). The powder needs to be reconstituted before use by combining it with a diluent that must never be frozen. After reconstitution, the vaccine must be used within six hours as it “rapidly loses potency.”
According to WHO estimates, almost 2 billion people worldwide are infected with Mycobacterium tuberculosis, the bacterium that causes TB. The disease is calculated to have infected 10.6 million people in 2021 as well as taken 1.6 million lives.
TB used to be widespread in the United States. However, it now infects less than 8,000 individuals annually in the country. According to the U.S. Centers for Disease Control and Prevention (CDC), 526 deaths were attributed to TB in 2019.
A new TB vaccine candidate developed by the Access to Advanced Health Institute (AAHI) was subjected to a Phase 1 clinical trial. AAHI’s single-vial TB vaccine is a freeze-dried formulation that can be stored at higher temperatures of up to 100 degrees Fahrenheit for months.
The AAHI vaccine has two parts—a fusion protein called ID93 and an immune-stimulating adjuvant called GLA-SE.
The Phase 1 trial looked at whether administering a thermostable single-vial regimen of ID93 and GLA-SE would be as effective as administering non-thermostable ID93 and liquid GLA-SE that are held in two vials and combined prior to injection.
Thermostable is a term used in biochemistry to refer to any substance that does not lose its characteristic properties when subjected to a moderate degree of heat.
Recipients of the single-vial formulation were found to have “robust T-cell responses” as well as producing higher levels of antibodies in blood than those who received the two-vial solution.
“The freeze-dried formulation does not require refrigeration and is mixed with sterile water just prior to injection. Thermostable vaccines are desirable in settings where maintaining cold or frozen vaccines for long periods can be costly and difficult,” according to a March 6 press release from the U.S. National Institutes of Health (NIH).
Better Vaccine Access
Dr. Corey Casper, CEO at AAHI, pointed out that equitable access to vaccines has been “significantly impeded” by the cold-chain requirements of existing TB vaccines, according to a March 6 press release.
“Adjuvanted subunit vaccines have re-energized the field of TB vaccine development,” said Christopher Fox, who leads the development of vaccine adjuvant formulations at AAHI.
“An effective thermostable TB vaccine would not only be better suited to reach areas of the world most burdened by the disease, but it would also mitigate costs and reduce wastage associated with more stringent cold-chain storage requirements.”
The vaccine is supported by the National Institute of Allergy and Infectious Diseases, part of the NIH.
An infection that invades the lungs, TB spreads through droplets in the air via sneezing or coughing. In the 19th century, it was known as “consumption.”
According to the CDC, some people have a higher risk of getting infected with tuberculosis. This includes individuals who have come into contact with someone who has infectious TB disease, and health care workers who live or work in places at high risk of TB transmission like jails, homeless shelters, and nursing homes.
People who are born in or travel frequently to nations where TB is common like Mexico, India, Vietnam, China, and so on are also at higher risk of getting infected.