Table 1.

Comparison between reported and expected numbers of cases.

n vaccinated (106)*	7.18
Annual incidence rate (10−6)	42.86
n expected cases	102.7
n reported cases (1981–99)	623
n eligible reported cases†	108
Poisson probability	0.31
Critical number (P < 0.05)	121
Critical under-reporting coefficient	1.12

^*20–44-year-old between 1 January 1994 and 31 December 1996

^†20–44-year-old subjects presenting with a first episode of CDD within 2 months after HB vaccine injection done between 1 January 1994 and 31 December 1996.