Russian scientists explore promising link between BCG vaccine & Covid-19 immunity explored in research review

The study claims it is possible the BCG vaccine won't be as effective in adults who weren't vaccinated as children.

A research team in St Petersburg University, Russia has found a link between countries where the bacille Calmette-Guerin (BCG) vaccine is given on a long-term and regular basis, and the severity of Covid-19 infection and mortality. Analysing some 100 academic papers and published statistics on the incidence of Covid-19 in various countries of the world, the data showed that the spread of the new coronavirus infection occurs more slowly where there is a large percentage of people vaccinated against tuberculosis with the BCG vaccine.

The data analyzed comes from Finland, China, Japan, Korea, and also countries in Eastern Europe, Central and South Asia, Africa, and the former USSR.

"The mortality rate turned out to be lower in those countries and areas where national vaccine immunization programmes have taken place for a long time or continue today, especially if revaccinations were practised," the researchers said in a press release Friday.

The trends observed in the data also suggest that the effect of BCG-linked immunity against Covid-19 comes from early and long-term influence of the vaccine strain on the immune system, i.e., if taken at a young age and in the proper vaccination schedule. This additional 'adjuvant' effect – wherein the response of the immune system is enhanced in a non-specific way – could act against multiple antigens including infectious ones like Covid-19.

"The causative agent of the new coronavirus infection and BCG have common peptides, which means that induction of cross-immunity is possible," one of the study authors Iana Ivashkevich, a graduate of the online General Pathophysiology program of St Petersburg University, is quoted as saying.

Many clinical trials of the BCG vaccine are underway, and trials of its use for in preventing the new coronavirus infection are being explored under different conditions. The researchers explain that the possibility of BCG vaccination decreasing the transmission and severity of COVID-19 is being actively explored in studies of international research teams from the USA, Germany, Canada, India, and Iran.

While the effect of BCG vaccination in adults is yet to be determined, the researchers said it's possible the vaccine won't be as effective in adults who weren't vaccinated as children.

"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," explained Dr Leonid Churilov, Deputy Head of the Laboratory of the Mosaic of Autoimmunity and Head of the Department of Pathology at St Petersburg University.

However, there are also contradictory studies that the BCG vaccine was less effective but still reduced the severity of the infection in adults.

"...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," Churilov added.

The study review has been published in the academic journal Juvenis scientia.

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