The spread of COVID-19 has panned out very differently in different countries. While in some such as the US, the UK and Italy, it has hit hard, in others such as Portugal, Poland and Israel, it seems to have barely dented the population. Although this could be due to multiple factors from more widespread social distancing to earlier political measures, researchers now suspect that a 99-year old tuberculosis vaccine may have something to do with the discrepancy.
Bacillus Calmette-Guern (BCG) childhood vaccination was developed in 1921 by French bacteriologists Camille Guerin and Albert Calmette to fight tuberculosis (TB). Usually administered shortly after birth, the vaccine is typically no longer used in high income countries due to its relatively low efficacy of just 60% in defending against TB, and an overall low risk factor of contracting the disease in these countries. It is still used however in the developing world.
Although not necessarily the most effective vaccine against TB, scientists have noticed that it may have some positive effects against other viral illnesses, respiratory infections and sepsis, and may be able to boost the body’s immune system.
One randomized trial of 2,320 babies in Guinea-Bissau in West Africa for example found that death rates among babies with low birth weights were significantly reduced after the vaccination. Further research including a 25-year study of more than 150,000 children in 33 countries found that those who had the vaccine were 40% less likely to develop acute lower respiratory tract infections than those who did not.
Meanwhile, another study looking at the vaccine’s effects among those aged 60-75 in Indonesia found those who had the vaccine were significantly less likely to develop acute upper respiratory tract infections than those in the control group.
These findings have then been supported by a recent analysis of coronavirus cases in middle and high income countries that have universal BCG vaccination policies and those that don’t. In this study, researchers found a correlation between the presence of universal BCG policies and fewer coronavirus cases and deaths per capita.
A good example of this is looking at Spain and Portugal. Although Spain does not practice the BCG vaccine, Portugal does. While Spain has the second highest rates of coronavirus cases and corresponding deaths in the world (at 140,511 and 13,897 respectively as of April 7th 2020), Portugal has just 12,442 cases and 345 deaths. This comes despite the proximity of the two countries on the Iberian peninsula.
Although encouraging findings, as of yet, there is still no firm link between one’s chances of developing severe symptoms from COVID-19 and whether or not they had the BCG vaccine. Thus, researchers in multiple countries including Australia and the Netherlands will soon start clinical trials to test this link, starting with physicians and nurses, who are at a higher risk of contracting the disease and developing severe symptoms. While the vaccine is not expected to eliminate one’s chances of becoming infected by the virus, researchers believe that it is likely to dampen its impact.