TABLE 1.

Seroprevalence of vaccinia-virus-specific IgG, as determined by ELISA, in four different birth cohorts that cover the period from before 1962 to after the cessation of routine smallpox vaccination in Japan in 1976

Birth yrNo. of subjectsNo. (%) of seropositive subjects
OD405 ≥ 0.10OD405 ≥ 0.30
Before 1962212209 (98.6)193 (91.0)
1962-1968144142 (98.6)130 (90.3)
1969-1975297196 (66.0)173 (58.2)
After 19752232 (0.9)0 (0)
Total876548495