The incidence and mortality rates of the COVID-19 infections vary widely across the countries, depending on their availability of human and material resources, level of Public Health preparedness and the authorities’ local and national responses. Also there might be differences in ethnic composition, dietary habits, climate differences, social determinants, genetic material, and civic institutions to consider. One of the latest influencing factors that caught the scientific attention is the degree of anti-tuberculosis immunization of the population with the BCG vaccine.

The Bacille Calmette—Guérin vaccine was prepared with a Mycobacterium bovis strain of the TB producing organism in the famous Institut Pasteur of Paris in 1921. Since then several variants have been produced in the developed and developing world. Those of us not born in the USA, still harbor the memory of the painful injection given in our primary school years that left a little scar on our right shoulder. The initial strain was distributed to several laboratories of the world and six major variants were produced: Pasteur 1173 P2, Danish 1331, Glaxo 1077, Tokyo 172-1, Russia BCG.I and Moreau RDJ. At present almost 100 million children are still been vaccinated worldwide; as the vaccine provides little immunity for adult pulmonary tuberculosis, it has been largely discontinued in most fairly developed countries.

The examples of Spain and Portugal are relevant for the vaccine’s importance. Spain, which never adopted the BCG vaccination nationwide, has a mortality rate of 336 people per million inhabitants. Portugal—a neighboring country that shares many of the Spanish societal and cultural features—adopted the BCG vaccination in 1965 and only has a mortality rate of 56 people per million inhabitants.

Abhibhav Shama et al., mathematical researchers from the School of Computer and System Sciences of Jawaharlal Nehru University of New Delhi, studied the COVID-19 data from countries that had either had vaccination or discontinued schedules or never had any vaccination. They said that: “disease incidence and morbidity are reduced in countries with universal BCG immunization compared with those that have not adopted the vaccine. The finding also applies to countries in which variables such as climate, dietary habits, and genetic origin essentially coincide.”

During its long utility, the BCG vaccine has shown protective benefits for patients with other diseases associated with mycobacteria like Leprosy. Being a strong immunomodulator, it has been used to treat bladder cancer and other neoplasias.

The researchers divided their morbidity results according to the BCG penetration:

  1. Countries without a universal BCG policy (Belgium, Italy, the United States and the Netherlands) have an increased incidence of 9 +- 497.1.
  2. Countries with an ongoing BCG policy have an incidence of 9+-155.6.
  3. Countries that discontinued the BCG policy have an intermediate value of67 +-509.89.

The mortality results were divided as follows:

  1. Countries with an active BCG policy have 4 +- deaths per million people.
  2. Countries that discontinued the BCG policy have 5+- 33.6 deaths per mil.
  3. Countries with no BCG policy had 1 +- 56.8 deaths per million people.

Considering that the COVID.19 infection affects the older individuals more than the younger ones, the researchers studied its incidence among different age groups. They found that: “The results indicate three significant features as follows: (i) the disease incidence is very low for subjects less than 15 years of age and does not show significant dependence on the presence or absence of universal BCG vaccination policies. (II) The number of infected cases across the age groups is always higher for countries without universal BCG vaccination policy. (III) The differences between countries with universal BCG vaccine policy and countries without such a policy increase and reach their peak for age groups 45-64 and 65-79 years old.”

The researchers found significant differences in countries that had used different variants of the vaccine or combinations of them. The Brazilian and Russian variants of the BCG vaccine were not deemed to work effectively against the coronavirus; in contrast the Australian variant of the vaccine seemed to confer more protection.

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