This particular study by Dr. Ashara should be viewed with great caution and the title of your article should be much more moderate. It should be noted that Ashara's work has not been peer reviewed or published in true academic journal.

First, let us summarize criticisms on using Diamond Princess for such gross estimations:

- Diamond Princess has 712 confirmed cases. Considering the serious limitations in diagnostics this number should be taken with care as well. However even if considered true it should be kept in min that this is a small sample size and there are numerous confounding factors involved, i.e. the passengers belong to the elderly upper class that is generally well nurtured and had received top quality medical care through life (with BCG or not)

- It is totally ridiculous to speculate on the arrival date of SARS-CoV-2 in different countries in Europe because: (i) EU is characterized with great people mobility across countries, (ii) most cases are asymptomatic or mild and patients had not visited a doctor, hence virus arrival date is impossible to be determined with any reasonable precision and (iii) actually there is no big time lapse between first diagnosed cases in different countries. Just an example on the last point (source: www.worldometers.info/coronavirus/#countries). BCG- countries: Italy- Feb 15, Spain- Mar 02, France- Feb 10, Netherlands- Feb-27, Belgium-Feb 28. BCG+ countries: Japan- Feb 15, Portugal- Mar 02, Poland- Mar 04, Hungary- Mar 04, Bulgaria- Mar-05, Latvia- Mar 02. The arrival of SARS-CoV-2 is approximately at the same time in both group of countries but the mortality is much different. The constraint measures in the East European countries are far from draconian compared to the implemented in the West. It is even more interesting if you see the Covid-19 mag in West and East Germany.

Indeed there are multiple confounding factors to be accounted but the Ashara's work is far more questionable compared to the BCG supportive studies.