London: A new study has found that countries with mandatory TB vaccination policies have fewer deaths from coronavirus than countries without such policies.
Preliminary study published on medRxiv, an unpublished medical research site, finds a correlation between countries asking citizens to get vaccinated against bacillus Calmette-Guerin (BCG) and those showing fewer confirmed cases and deaths due at Covid-19. Although this is only a correlation, clinicians in at least six countries are conducting trials of giving front-line health workers and the elderly BCG vaccine to see if it can actually provide some level of protection against the new coronavirus.
Gonzalo Otazu, assistant professor at the New York Institute of Technology and lead author of the study, started working on the analysis after noticing the low number of cases in Japan. The country has reported some of the first confirmed cases of coronavirus outside of China and has not put in place lockdowns like so many other countries have done.
Otazu said he was aware of studies showing that the BCG vaccine offered protection not only against TB bacteria but also against other types of contagions. His team therefore gathered data on which countries had universal BCG vaccine policies and when they were implemented. They then compared the number of confirmed cases and deaths due to Covid-19 to find a strong correlation.
Among high-income countries with large numbers of Covid-19 cases, the United States and Italy recommend BCG vaccines but only for those who may be at risk, while Germany, Spain, France and the United Kingdom previously had BCG vaccination policies but ended them decades ago. China, where the pandemic started, has a BCG vaccination policy but it was not followed very well until 1976, said Otazu. Countries like Japan and South Korea, which have been successful in controlling the disease, have universal BCG vaccine policies. Data on confirmed cases in low-income countries were found to be insufficiently reliable to make a solid judgment.
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With nearly 900,000 cases and 45,000 deaths, the world is struggling to control Covid-19. Any vaccine against the disease is more than a year away from being available, and the effectiveness of the test drugs will not be known in the coming months. That’s why it’s reasonable to question whether the BCG vaccine could provide protection against Covid-19, said Eleanor Fish, professor in the Department of Immunology at the University of Toronto. Otazu’s study has not yet been peer reviewed, a strict criterion for scientific study.
“I would read the study results with incredible caution,” said Fish.
Otazu, who said he has already received comments from other experts, is working on a second version of his study that will address some of their concerns. It also submitted the study for a formal review process with Frontiers in Public Health.
One of the first to test the efficacy of the BCG coronavirus vaccine is Mihai Netea, an infectious disease expert at the Radboud Universty Medical Center in the Netherlands. The Netea team has already recruited 400 health workers for the trial – 200 have received the BCG vaccine and 200 have received a placebo. He doesn’t expect to see results for at least two months. He is also about to start a separate trial to study the effectiveness of the BCG vaccine in people over the age of 60. Other trials are underway in Australia, Denmark, Germany, the United Kingdom and the United States.
Scientists are still working to better understand why the BCG vaccine can be effective not only against tuberculosis but against other pathogens. Netea’s work over a decade shows that the BCG vaccine sensitizes the immune system in such a way that, whenever a pathogen that relies on the same attack strategy as attacks by the tuberculosis bacteria, it is ready to respond in a better way than the immune system of those who did not get the vaccine.
“It’s like the BCG vaccine creates bookmarks that the immune system can use later in life,” Netea said.
Even if the BCG vaccine proves effective, it is not a reason to store.
“People should not accumulate or try to get BCG vaccination like they did with toilet paper,” said Otazu. There is a small chance that the BCG vaccine may increase the risk of coronavirus, but scientists will not know until after clinical trials.
In any case, the BCG vaccine should not be the only tool to fight Covid-19.
“No country in the world has succeeded in controlling the disease simply because the population was protected by BCG,” said Otazu. Social distancing, screening and isolation of cases should be implemented to manage the spread of the disease.
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