This article is from the Childhood Vaccinations FAQ, by Lynn Gazis-Sax firstname.lastname@example.org with numerous contributions by others.
This claim is examined at length by Lon Morgan, DC,DABCO in his Web
site "A summary of JAPAN, SIDS, and PERTUSSIS IMMUNIZATION" at
turns out that what
went away, in 1975, when Japan increased the age at which it
administered the first dose of the vaccine from three months to
two years, was *claims of vaccine injuries* for SIDS. Japan had a
compensation system for vaccine injuries, in which claims were to be
paid unless other causes were clearly provable. Under this system, 11
claims were paid for what was termed Sudden Death, between 1970-1975
(this out of 25-30 million doses of pertussis vaccine). After the
vaccination age was raised, no further claims were paid for Sudden
Death related to vaccination. Since SIDS occurs before 12 months of
age, any cases of SIDS can not be attributed to a vaccine which is
given starting at 24 months.
Japan has, however, kept statistics for SIDS, and these statistics
showed the numbers of SIDS cases *increasing*, rather than decreasing,
at the time that the age of the first pertussis vaccination was
raised. Though the delay in age for the first pertussis vaccination
did not reduce the incidence of SIDS, it did result in a huge increase
in pertussis cases, peaking at 13,105 cases and 41 deaths by 1979. For
more details, and references, see Lon Morgan's site.
As a side note, recent vaccination rates for Japan, as listed in
http://www.who.int/gpv-surv/country/japan.html, were, in 1996, 98% for
polio, 100% for diptheria, pertussis, and tetanus, and 94% for
measles; the coverage for BCG in 1993 was 91%.