Period 1997–1998* | 1997 | 1998 | Mean incidence | |
---|---|---|---|---|
13.2 (79)** | 7.3 (44) | 10.3 (123) | ||
Period 2000–2002*** | 2000 | 2001 | 2002 | Mean incidence |
before vaccination | 1.1 (7) | 2.5 (15) | 0.5 (3) | 1.4 (25) |
after vaccination | 0.0 (0) | 0.2 (1) | 0.7 (4) | 0.3 (5) |
total | 1.1 (7) | 2.7 (16) | 1.2 (7) | 1.7 (30) |