“If you superimpose a map of the world with coronavirus over countries that had a BCG vaccine program, there appears to be less virulent spread of COVID-19 in countries that inoculated children against tuberculosis. The number of cases may still be high, but the fatality rate is lower in BCG countries,” explains Sameer Mani Dixit, a researcher at the Centre for Molecular Dynamics in Kathmandu.
He adds that the BCG is not an anti-virus vaccine, but seems to build the body’s immunity not just against tuberculosis, but also from viral infections. Recent research suggests that live attenuated vaccine like BCG stimulates the immune system and protects against wide range of diseases. It is also important to note that the vaccine is no means perfect, as it prevents about 60% of TB cases among children. In addition, the vaccine is less effective in preventing TB that affects the lungs and works better against severe forms of TB, such as tuberculosis meningitis.
BCG vaccine’s effectiveness against COVID-19 is a hypothesis that is yet to be tested, researchers are starting clinical trials in Australia, the Netherlands and Germany that should answer the questions surrounding BCG in the near future. The trials are being conducted on people at high risk of exposure, primarily health care personnel.
Buddha Basnyat, a physician at Patan Hospital believes that without randomised control trials the efficacy of BCG against COVID-19 is “just a conjecture”, and the tests need to prove beyond doubt that there is a correlation.
“The link is unknown and it would require a lot of scientific studies to find the truth. Only, when the results of clinical trials are out can we be absolutely certain. In medicine, association is not enough, we need to show causal linkages, especially when there are so many confounding variable. Until then nothing is concrete,” adds Basnyat.
Furthermore, it is also necessary to know for how long does the positive effects induced by BCG lasts in the immune system. Nepalis were vaccinated with BCG as infants, would that protect them as adults? Keeping a vigilant eye on the number of novel coronavirus cases in the BCG vaccinated countries is important. An exponential spread of COVID-19 cases in India could knock out the hypothesis completely, and there is also no explanation why China which has near universal BCG coverage was so badly hit.
We could be clinging to straws, hoping that the BCG vaccine will save the day, but the authenticity of the hypothesis cannot be established till it is explored through rigorous clinical trials. Till then, public health experts warn, Nepal needs to maintain its lockdown, test and isolate groups around the country, especially western Nepal where tens of thousands of Nepali workers have come in from India in recent weeks.
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