New Delhi: Scientists from St. Petersburg University, Russia, have analysed data detailing Covid-19 spread in several countries to find that “new coronavirus infection occurs more slowly where there is a large percentage of people vaccinated against tuberculosis with the BCG vaccine”.
The effect of the Bacillus Calmette-Guerin (BCG) vaccine on immunity against Covid-19 is currently being investigated across the world, with some earlier studies deriving similar conclusions as well. India is one of the countries where BCG, which guards against tuberculosis, is part of the immunisation programme for children.
“…This vaccination itself, given in early childhood, changes the immune system in such a way that the new coronavirus disease course tends to be less severe,” the Russian scientists said in a press release.
The researchers from St. Petersburg University added that they “have analysed about 100 academic papers and statistics” on the spread of Covid in different countries to arrive at their conclusion. Their study has been published in the Russian peer-reviewed journal Juvenis scientia.
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Analysis of Covid spread
The researchers say they have found an “association” between countries where BCG is given on a long-term and regular basis, and “the incidence of Covid-19, the course of acute interstitial pneumonia caused by infection, and the mortality rate from it”.
“The mortality rate turned out to be lower in those countries and areas where national vaccine immunisation programmes have taken place for a long time or continue today, especially if revaccinations were practised,” the researchers said in the press release, issued in English.
According to the study, this association was found in Finland, China and Japan, as well as in countries in Eastern Europe, Central and South Asia, Africa, and the former USSR.
“The figures are significantly higher where large-scale BCG vaccination has never been practised or stopped more than 20 years ago, for example, in the USA, Italy, the Netherlands, Belgium, and Germany excluding the lands of the former East Germany,” the study authors said.
Also read: ICMR data shows BCG vaccine raises immune response in elderly, could protect against Covid
How it works
Simply put, the BCG vaccine triggers a “trained” or innate and adaptive immune system response within our bodies, which could offer protection against severe Covid-19, the researchers state.
According to the St. Petersburg scientists, “it is the early and long-term influence of the vaccine strain on the developing immune system that provides an adjuvant effect — it enhances the body’s immune reaction to various antigens, including many infectious ones”.
In other words, this protection is most likely when the vaccine is given at a young age, in countries that have practised BCG immunisation for a long period of time.
“There is reason to believe that in adults and elderly people who were not vaccinated in early childhood, the effect of late vaccine administration will be significantly less,” said Leonid Churilov, the scientist who supervised the study, as quoted in the press release.
“At the same time, there are research papers by scientists from the Netherlands, where BCG is not given in childhood. They indicate that BCG administration to adults does not worsen, and, perhaps, somewhat attenuates the course of the disease when infected with the new coronavirus,” he added.
In October, scientists from the ICMR National Institute for Research in Tuberculosis found, in a non-peer-reviewed study, that administering BCG vaccine could increase the trained, adaptive immunity in older adults, which could help protect against Covid-19.
“When the BCG vaccine is given at a young age, one can get lots of T memory cells which can help fight a coronavirus infection. But there are studies that show BCG can also mount an immune response in adults,” said Dr Gobardhan Das, professor of molecular medicine at JNU and among the early proponents of using the BCG vaccine against Covid-19.
“When coronavirus enters BCG-vaccinated individuals, the innate memory generated by BCG paves the way for generating Covid-antigen-specific T cells. This may lead to generation of specific vaccine efficacy against Covid, which may protect in future exposure,” he added.
Also read: Countries with BCG vaccine policy have slow Covid infection and death rates, US study finds