Table 2.
Incidence of trivalent inactivated influenza vaccine (TIV)-associated febrile convulsions and other febrile reactions in children aged 6 months to 4 years in Western Australia, by vaccine brand and formulation, for the period 8 March to 25 April 2010
| Fluvax |
Fluvax Junior |
Combined Fluvax and Fluvax Junior (CF) |
Influvac |
CF vs Influvac† |
|||||||
| n/N* | Rate/1000 TIV doses (95% CI) | n/N | Rate/1000 TIV doses (95% CI) | n/N | Rate/1000 TIV doses (95% CI) | n/N | Rate/1000 TIV doses (95% CI) | RR (95% CI) | p Value | ||
| Febrile convulsions‡ | ≤2 years | 28/5754 | 4.9 (3.4 to 7.1) | 23/2915 | 7.9 (5.3 to 11.8) | 51/8669 | 5.9 (4.5 to 7.7) | 0/2124 | 0 (0 to 1.8) | Undefined | <0.001 |
| 3–4 years | 7/5015 | 1.4 (0.7 to 2.9) | 4/413 | 9.7 (3.8 to 24.7) | 11/5428 | 2.0 (1.1 to 3.6) | 0/2596 | 0 (0 to 1.5) | Undefined | <0.05 | |
| All <5 years | 35/10769 | 3.3 (2.4 to 4.6) | 27/3327 | 8.1 (5.6 to 11.8) | 62/14096 | 4.4 (3.4 to 5.6) | 0/4720 | 0 (0 to 0.8) | Undefined | <0.0001 | |
| Other febrile reactions§ | ≤2 years | 282/5754 | 49.0 (43.7 to 54.9) | 138/2915 | 47.3 (40.2 to 55.6) | 420/8669 | 48.4 (44.1 to 53.1) | 9/2124 | 4.2 (2.2 to 8.0) | 11.4 (5.9 to 22.1) | <0.0001 |
| 3–4 years | 127/5015 | 25.3 (21.3 to 30.0) | 11/413 | 26.6 (14.9 to 47.0) | 138/5428 | 25.4 (21.5 to 29.9) | 2/2596 | 0.8 (0.2 to 2.9) | 33.0 (8.2 to 133.2) | <0.0001 | |
| All <5 years | 409/10769 | 38.0 (34.6 to 41.8) | 149/3327 | 44.8 (38.3 to 52.4) | 558/14096 | 39.6 (36.5 to 42.9) | 11/4720 | 2.3 (1.3 to 4.1) | 14.8 (8.3 to 26.7) | <0.0001 | |
n/N indicates number of febrile convulsions or other febrile reactions/adjusted number of doses given within age group and vaccine category.
RR, 95% CI and p value calculated for comparison of rates of adverse events for the combined Fluvax and Fluvax Junior group, versus Influvac. The RR and p value for the ‘All <5 years’ category is weighted for age.
Febrile convulsion presentations derived from notifications received via the AEFI reporting system and from emergency department ICD-10 diagnostic code R56.0 ‘febrile convulsion’.
‘Other febrile reactions’ derived from passive reports by doctors, other immunisation providers and parents to the AEFI reporting system.
AEFI, adverse event following immunisation; TIV, trivalent inactivated influenza vaccine.