| 2001 | 2002–2003 | | 2003 | | 2003–2004 | | 2004 | |
| Previous | Winter | Spring | Summer | Autumn | Winter | Spring | Summer | Autumn |
Follow-up subjects n (death n) | | | | | | | | | |
Vaccinated | 647 | 647 | 575 | 547 | 532 | 506 | 484 | 461 | 453 (54) |
Developed pneumoccocal infection | 4.0 | 3 | 5 | 1 | 1 | 2 | 0 | 0 | 0 |
Unvaccinated | 731 | 731 | 628 | 612 | 593 | 577 | 554 | 526 | 499 (31) |
Developed pneumoccocal infection | 1.5 | 4 | 1 | 0 | 1 | 4 | 2 | 0 | 1 |