We have been hearing a lot about BCG lately, but what does it protect from exactly?
BCG, Calmette and Guérin's vaccine, was first used in 1921 to stem the spread of tuberculosis and has been in use ever since. Even though it is no longer mandatory in many countries, it is still widely administered in high TB burden countries around the world.
Within the past days and weeks, we have seen a growing interest in this vaccine due to news of studies indicating a possible correlation between BCG vaccination and lower rates of COVID-19 deaths. It is important to note that these studies were not peer-reviewed and further trails will be necessary to confirm this link. While this correlation needs to be substantiated, this is a good time to understand how BCG works, what it protects from and what improvements should be made. This will also help us dismiss misinformation and fake news around the vaccine.
This very old vaccine, composed of living but weakened tuberculosis bacilli, was adopted with suspicion because of its relative effectiveness. A century after the first human inoculation, 10 million people still fall ill and 1.5 million people die because of TB.
In a statement in 1997, the World Health Organization (WHO) attributed the failure of the global fight against tuberculosis to several reasons, including "exaggerated confidence in BCG." Indeed, BCG “protects against severe extra-pulmonary forms of pediatric tuberculosis. However, it does not reliably protect against pulmonary tuberculosis, which accounts for the largest share of the burden of the disease in the world" said WHO, which advocates for the development of new and effective vaccines, drugs and diagnostics.
BCG should still be used to help preventing the extra-pulmonary forms of TB, and new and effective vaccines should be developed. In the last years, the efforts and investments have ramped up and there are promising new drugs and vaccines in the pipeline, but the gap in research & development (R&D) for TB investments is still very high. Considering the increasing threat of drug-resistant TB, an effective vaccine could be the most powerful tool to contain the spread and finally put an end to this ancient, but preventable disease.