The story that BCG vaccine protects against COVID-19, seems to many a story. But this is not a joke. In the world undergo several clinical trials of its effectiveness. But Israeli scientists have recently published a study that BCG does not help.
Does this mean that in this matter you can put a point and to stop the clinical trials of TB vaccines to protect against coronavirus infection? Because the article Israeli physicians was published on the website of the influential “Journal of the American medical Association” (JAMA), and just dismiss it. Let’s understand this question.
In March, it was noticed that in Russia, Japan, both Koreas, Romania, Croatia and other countries where polls and be sure to carry out BCG vaccination, the morbidity rate COVID-19 slower, and the mortality rate is lower than in countries where tuberculosis is not vaccinated. The latter include the notorious U.S. and Italy, and also Belgium, the Netherlands and Canada, where the situation is not good. In these countries, BCG is mandatory I’ve never done. Intermediate position occupied the country, where in the past BCG was made mandatory, but then stopped. Among these countries were Turkey and Israel.
Here vaccination of newborns has been mandatory since 1955 to 1982. After that, it began to make only immigrants from countries with unfavorable situation with tuberculosis. To test the hypothesis, scientists from tel Aviv compared the number of positive tests COVID-19 among people born 1979-1981 and 1983-1985 That is in the first group BCG vaccine was administered to almost all (in Israel, it was all strictly), and the second — almost anyone. It’s also important that the age of the two groups differed not too critical, first it was 40 years in average, the second — 35. Statistically significant difference between positive tests in both groups was not found. From this the scientists concluded: “This study does not confirm the idea that BCG vaccination in childhood has a protective effect against COVID-19 in adulthood”. In this case separately stipulated, that due to the small number of severe cases was impossible to conclude about the relationship between BCG vaccination and severity of coronavirus infection.
Final clarity no
“Obviously, vaccination against tuberculosis does not directly affect the prevalence and severity COVID-19, — says associate Professor of infectious diseases at children rnsmu. Pirogov, candidate of medical Sciences Ivan Konovalov. — The fact that in a study conducted in Israel, the incidence of COVID-19 did not differ significantly among people who were vaccinated with BCG vaccine, and those who are not introduced no evidence that such vaccinations do not affect non-specific immunity. However, in order to Express the relationship between BCG vaccination and COVID-19, may be need more data obtained in the survey more people. In addition, it is necessary to consider individual characteristics of patients: gender, age, presence of comorbidities, etc. They can significantly influence susceptibility to coronavirus and the severity of COVID-19.
In addition, it is important to note that the BCG in different countries are slightly different and you need to evaluate the effectiveness of the stimulation of nonspecific immunity to each of them separately. For example, in Russia there are two types of such vaccines, made on the basis of the line of strain of BCG (Russia). And each type has its own indications. In Europe and Asian countries included in the vaccine strains of BCG other lines, formed naturally before the mid-twentieth century.”
BCG is not as simple as it seems
It would seem that where the TB and where coronavirus infection? What could be a vaccine against first infection efficacy against the second? It turns out that there is a connection, and hope physicians are not unfounded. Of course, we are not talking about the fact that BCG causes the production of antibodies against the coronavirus. The effect of the tuberculosis vaccine non-specific. Explaining it, the experts use such terms as “training of immunity” and “innate immunity”. The mechanisms of this extremely complex, and they can not explain. But I think even people far from immunology, concerned with the question: why is this valid only BCG and not other vaccines, which weight?
The explanation there is. It is the most ancient of vaccine used today. Next year it will be exactly 100 years. In 1921, it was created at the Pasteur Institute in France Alber Calmet and Camille guérin. First, they worked with the bacterium that causes tuberculosis in cattle (bovine tuberculosis). They managed to weaken her so that she was safe for animals and humans. In honor of them this relaxed (atenuatorul) bacterium called Bacillus Calmette–Guérin (BCG). And in Russia, this abbreviation was transformed into BCG.
This live bacteria is, in fact, is the vaccine against tuberculosis. Now a new vaccine do anyway. For them to try to use even “dead” (killed bacteria and viruses), and only their fragments, and even better — some antigens. These vaccines are intricate, they the immune system produces a specific protective antibodies. But BCG is causing a major shake-up immunity, in addition to antigens it has and other stimuli. And so it leaves a trail that many other infections can not penetrate immunity.
It is known that BCG protects against leprosy. And according to some, and even from many viral infections, reducing the risk of infecting them by 30%. In 2017, was published a major study in which BCG has protected volunteers against infection with attenuated yellow fever virus. In the experiment, people can not infect real threat of germs, but it is important that the scientists found significant changes in the immune system, sufficient to reflect this virus attack. So BCG is not so simple, maybe we still wait for its success in the war against coronavirus. And then the century of vaccines, the whole world will celebrate a great triumph.