Table 1.
Number and Percentage of Invasive Meningococcal Disease Cases by Serogroup and Year and the Incidence Rate Ratios, the Netherlands, January 2015 to June 2018
| 2015 | 2016 | 2017 | 2018a | 2018a vs 2015a | ||||||
|---|---|---|---|---|---|---|---|---|---|---|
| Serogroup | n (%) | IR (/100 000) | n (%) | IR (/100 000) | n (%) | IR | n (%) | IR (/100 000) | IRR (95% CI) | P Value |
| W | 9 (10.0) | 0.05 | 50 (33.1) | 0.29 | 80 (40.4) | 0.47 | 65 (50.8) | 0.76 | 16.0 (5.8–43.9) | <.001 |
| B | 65 (72.2) | 0.38 | 77 (51.0) | 0.45 | 81 (40.9) | 0.47 | 47 (36.7) | 0.55 | 1.4 (.9–2.3) | .106 |
| Y | 7 (7.8) | 0.04 | 17 (11.3) | 0.10 | 27 (13.6) | 0.16 | 12 (9.4) | 0.14 | 2.4 (.8–6.7) | .096 |
| C | 8 (8.9) | 0.05 | 6 (4.0) | 0.04 | 9 (4.5) | 0.05 | 3 (2.3) | 0.03 | 0.6 (.1–2.5) | .465 |
| Total | 89 (100) | 0.53 | 150 (100) | 0.88 | 197 (100) | 1.15 | 127 (100) | 1.48 | 2.7(1.9–3.8) | <.001 |
Two cases of IMD-E (one case) and IMD-X (one case) not included in the table.
Abbreviations: CI, confidence interval; IMD, invasive meningococcal disease; IR, incidence rate; IRR, incidence rate ratio.
aData for comparison included January to June 2015 versus January to June 2015.