The link below is really fascinating (and "not crazy" according
to at least one medical faculty member colleague here).
The idea is that folks who got the
old fashioned TB vaccine as infants have some limited
protection against covid19. You can read the article but
this would help explain many observations:
*The disease is spreading particularly quickly (and perhaps
with higher mortality) in Western Europe and USA
compared with places that have had and still have
mandatory TB vaccination for infants,
including basically all of Asia.
Japan is a particularly interesting case as they had
large numbers of Chinese visitors in the early days of
the pandemic, have not had a real lockdown and
their public health response has probably been at the
US or Italy level (not like in S. Korea or Taiwan)
Somehow the bodies are not piling up in Japan like
in Italy, Spain, New York (so far).
*Former East Germany has many fewer cases than former West Germany
*In Canada cases are suppressed among folks >50-60 years of
age compared to expectations. Canada (unlike the US) had
widespread "customary" TB vaccination for infants until it was stopped in the 1960's-70's.
https://www.jsatonotes.com/2020/03/if-i-were-north-americaneuropeanaustral.html?m=1