Table 5.
Crude and adjusted relative risk estimates (odds ratio and 95% confidence intervals) for Guillain-Barré syndrome after pandemic influenza A (H1N1) 2009 vaccination according to timing of vaccination (≤6 weeks or >6 weeks) before onset of symptoms
| Unadjusted matched analysis* | ILI/URTI adjusted only | Adjusted for seasonal influenza vaccination only | Adjusted for seasonal influenza vaccination and ILI/URTI | |
|---|---|---|---|---|
| Denmark: | ||||
| None | Reference | — | — | — |
| ≤6 weeks | 9.5 (1.7 to 53) | — | — | — |
| >6 weeks | 3.4 (0.7 to 17) | — | — | — |
| Netherlands: | ||||
| None | Reference | Reference | Reference | Reference |
| ≤6 weeks | 2.5 (0.7 to 9.3) | 1.3 (0.3 to 6.1) | 1.7 (0.3 to 8.8) | 0.6 (0.1 to 4.4) |
| 1 dose | 0.7 (0.1 to 6.0) | 0.2 (0.0 to 4.2) | 0.5 (0.1 to 5.1) | 0.2 (0.01 to 4.3) |
| 2 doses | 6.8 (1.3 to 36) | 5.3 (0.6 to 44.1) | 6.2 (1.1 to 35.4) | 6.9 (0.6 to 81.0) |
| >6 weeks | 1.7 (0.4 to 6.4) | 0.9 (0.2 to 4.2) | 0.7 (0.1 to 4.8) | 0.2 (0.02 to 1.6) |
| Missing dates | NC | NC | NC | NC |
| Sweden†: | ||||
| None | Reference | Reference | Reference† | Reference† |
| ≤6 weeks | 2.3 (0.5 to 11.7) | 1.8 (0.3 to 10.7) | 2.4 (0.5 to 11.8) | 1.8 (0.3 to 12) |
| >6 weeks | 0.9 (0.2 to 4.9) | 1.0 (0.2 to 6.3) | 1.2 (0.2 to 6.3) | 1.3 (0.2 to 8.5) |
| Missing date | 0.3 (0.03 to 3.5) | 0.5 (0.0 to 5.5) | 0.4 (0.0 to 4.0) | 0.6 (0.1 to 6.8) |
| UK: | ||||
| None | Reference | Reference | Reference | Reference |
| ≤6 weeks | 1.3 (0.3 to 6.4) | 1.1 (0.2 to 5.7) | 0.7 (0.1 to 4.2) | 0.7 (0.1 to 4.1) |
| >6 weeks | NC | NC | NC | NC |
ILI/URTI=influenza-like illness or upper respiratory tract infection; NC=not calculated because of low numbers.
*Matched on age (within 1 year), sex, and index date; additionally matched on GP practice in Netherlands and UK
†No cases exposed to seasonal influenza vaccination (possible under-reporting).