Study: Tuberculosis Vaccine May Only Protect Children Under Age 5

Tuberculosis affects millions of people worldwide, but the only known vaccine may only protect children who are 5 years of age or younger.

A recent study conducted by researchers at the Boston University School of Public Health (BUSPH) showed that the bacille Calmette-Guérin (BCG) vaccination for tuberculosis (TB) only protected children 5 years of age and under, whereas older adolescents and adults did not have the same level of protection.

The results suggest that the efficacy of the BCG wanes as children grow up. The researchers recommend getting a TB vaccine booster after 10 years of age, plus getting an additional supplemental vaccine.

“Our findings indicate that BCG vaccination is effective at preventing tuberculosis in young children. Since tuberculosis in children is a highly debilitating and severe disease, BCG vaccination should continue to be used,” said Dr. Leonardo Martinez, study lead author and assistant professor of epidemiology at BUSPH, in a press release. “Unlike many of the mRNA COVID-19 vaccines, which we know are highly effective, there is widespread debate on the BCG vaccine’s effectiveness and duration of protection, as well as whether the vaccine only works in selective settings.”

Even if this is the case, “boosting immunoprotection is needed for older populations,” Martinez explained. “Novel vaccines are urgently needed to supplement BCG vaccination in high-burden settings.”

The almost 100-year-old vaccine is one of the most common immunizations administered worldwide. More than 10 million people are infected with TB yearly, and BCG remains the only vaccine for the disease.

Martinez and his team of researchers examined the impact of BCG vaccination for all TB disease, specifically pulmonary and extrapulmonary TB. Referencing 26 longitudinal studies, the team analyzed individual-level data of nearly 70,000 participants who were exposed to TB from 1998-2008.

Martinez and team looked at the use of skin and blood TB infection tests to examine study variability—they also accounted for HIV, exposure status, TB history, and other possible confounding factors.

BCG vaccination was 37% effective in children younger than 5 years of age. The vaccine could not conclusively protect adults or children older than 10 years of age, according to the study. Most TB cases in high-income countries are among immigrants who come from countries with high rates of the disease, according to Martinez.

“Several cost-effectiveness and mathematical modeling studies have found that devoting resources to countries with a high burden of tuberculosis outside the US is amongst the most effective intervention to control tuberculosis inside the US. So, although our results are mostly in settings with a high burden of tuberculosis, they are also relevant to low-burden settings,” Martinez said in a press release.

The team recommends investing in a n effective TB vaccine to control the global spread of the disease.

“We urgently need vaccines that are effective against TB in adults,” added study coauthor Dr. C. Robert Horsburgh, professor of epidemiology, in a press release. “There are a number of promising TB vaccine candidates under study and we hope that one or more of them will prove effective.”

This study was published in The Lancet Global Health.

Reference

BU study: BCG vaccine prevents tuberculosis in young children, but not adults. EurekAlert! Aug 9, 2022. Accessed on Aug 10, 2022.