On 2020-04-01 16:36:48, user japhetk wrote:
The study seems interesting.
However, the problems of this study's analyses, are as mentioned in the comments, <br />
they are not controlling when the infection spread in the country.
Other analyses are controlling that (for example, number of patients (or
deaths) 10 days after the 100th patients were detected, was used as a dependent measure).
Also, probably, the most accurate available BCG measure is "how long the country has advanced the BCG vaccination measure" (the year when the country stopped the BCG vaccination (or now, when the BCG vaccination is currently conducted in the country) - the <br />
year when the country started it). The current measure is not indicative as authors indicated.
I controlled these measures and have done the analyses.
The results were as follows.<br />
The partial correlation between "how long the country has advanced the BCG vaccination measure" and number of patients in the 10th day (when 1st day is 100th patients were detected in the country) after controlling the population of the country. P = 0.455, partial correlation coefficient = -0.116
The partial correlation between "how long the country has advanced the BCG vaccination measure" and number of deaths in the 10th day (when 1st day is the 100th patients were <br />
detected in the country) after controlling the population of the country. P = 0.111, partial correlation coefficient = -0.243
But the partial correlation between "how long the country has advanced the BCG vaccination measure" and when the 100th patients were detected in the country after controlling the population of the country was P = 0.078, partial correlation coefficient = 0.281.
Also "how long the country has advanced the BCG vaccination measure" is <br />
robustly and negatively correlated with GDP of the country after controlling the population of the country (p = 0.019, partial correlation coefficient: -0.292).
Also "how long the country has advanced the BCG vaccination measure" is robustly and negatively correlated with how fast the 100th patients were detected in the country (p = 0.078, partial correlation coefficient: 0.281).
But the correlation between GDP of the country and when the 100th patients were detected in the country after controlling population of the country was more robust (P = 0.001, partial correlation coefficient = -0.438).
And the correlation between "how long the country has advanced the BCG vaccination measure" and when the 100th patients were detected in the country disappeared when the population and GDP is also controlled (p = 0.322).
The partial correlation between "how long the country has advanced the BCG vaccination measure" and number of deaths in the 10th day after controlling the population and GDP of the country was P = 0.178, partial correlation coefficient = -0.210.
So, my guess is probably, there are number of spurious correlations happening in authors' analyses due to lack of important control variables, even if there are real correlations, they apparently should not be that strong (studies of the BCG's universal effects have not <br />
indicated such things either).
In Korea, China, Japan (diamond princess), the virus infected a lot of people in some regions or situations, too.
The countries of higher GDP can do more tests, they are more popular to the tourists from Asia, but they were perhaps less inclined to use masks, they were confident of their medical system and less alert. And those are the countries where BCG was "no longer necessary".
Remember one month ago, the coronavirus is an infectious disease of Asian people. Now it is an infectious disease of Western countries, who knows if it is not the disease of developing countries in the next few months.