LONGITUDINAL study data reveals that immune protection following the bacille Calmette–Guérin (BCG) tuberculosis (TB) vaccine wanes after 5 years. The study conducted by Leonardo Martinez, Department of Epidemiology, School of Public Health, Boston University, Massachusetts, USA, and colleagues, was performed in response to concerns about the longevity of protection offered by the BCG vaccine following administration in infancy.
The researchers assessed BCG vaccine efficacy at protecting against TB disease by looking at data from 26 longitudinal studies from 17 different countries, including almost 70,000 persons who had been exposed to TB between 1998 and 2018.
The results showed that following vaccination in infancy, immunoprotection against TB wanes after 5 years of age. In terms of efficacy, the BCG vaccine was found to be 37% effective in children under 5 years of age and showed no conclusive evidence of protection in persons over 10 years of age. On stratification to pulmonary TB alone, the BCG vaccine offered effective protection in 19% of children under 5 years of age. Study lead Martinez highlighted the severity of illness that TB causes in young children, and for this reason, stated that “BCG vaccination should continue to be used” in children under 5 years of age.
However, the authors reported that due to the waning protective immunity offered by the BCG vaccine with age, a BCG booster vaccination should be offered to adults and children over 10 years of age. Experts report that there is diminished effect when using the BCG vaccine as a booster, and for this reason, new TB vaccines are required. Further to this, new TB vaccines could also offer support to the current BCG vaccination programmes in endemic areas. In order to achieve this, significant TB vaccine development funding will be necessary.
Study co-author, Robert Horsburgh, Department of Epidemiology, School of Public Health, Boston University, Massachusetts, USA, emphasised the urgent need for effective adult TB vaccines and stated: “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 highlights that booster vaccines should be considered in those over 10 years of age, and that there is a need for improved TB vaccines that can offer longer protection and support vaccination programmes in endemic areas.