[A summary of characteristics of the first wave of new type coronavirus epidemic and potential association with tuberculosis vaccination].

Introduction: The new type of coronavirus (SARS-CoV-2) epidemic is widespread throughout the world. During the outbreak of the pandemic in Europe it was revealed that the rate of spread was lower in countries where extensive BCG vaccination is used to protect against tuberculosis. Objective: In the present work, we sought to explore relationships that influenced epidemic spreading parameters, with particular reference to BCG vaccination practice. Methods: We examined the first wave of the spread of the epidemic for all countries in the world where adequate quality statistics were available. We analyzed the duration of the epidemic, the extent of the peak, the number of infected people, and the number of deaths per million inhabitants with the moving average of epidemic curves. We took into account the economic indicators of the countries (GDP, air traffic and extent of maritime shipping). Statistical analysis: The examined parameters did not show a normal distribution, so we looked for a statistical relationship with non-parametric tests (rank correlation, Kruskal–Wallis ANOVA) between the extents of epidemic spread, BCG vaccination and other parameters. Results: The epidemic spread rapidly around the world, but still, in the first three weeks of February, there was a pause in the spread. The first wave of epidemics ended roughly at the same time in Europe. Those countries are the most affected by the epidemic where regular BCG vaccination has not been used, although the picture is complicated by the fact that these countries are mostly economically developed. There was no such difference observable in the mortality rate. Conclusion: Although this work clearly demonstrates that during the first wave of the pandemic, fewer infections were reported worldwide in countries where BCG vaccination is obligatory, however, the causal relationship is uncertain, as the countries’ past, customs, social organization and economic development are different. Our results support the necessity of comparative contact tracing to clarify how BCG vaccination affects people’s susceptibility to this new type of coronavirus as well as their ability to spread and transmit the virus. Orv Hetil. 2021; 162(4): 123–134.