Table 2

Association between inactivated influenza vaccine, vasculitis and unexplained fever*

OutcomeRisk periodEvents (n)Person-time (days)Incidence rate ratio (95% CI)P values
Vasculitis
Unexposed8930 9361.000.906
15 days prevaccination518150.95 (0.38 to 2.33)
Postvaccination intervals
0–14 daysX1 16940.41 (0.10 to 1.65)0.207
15–30 days518150.95 (0.38 to 2.33)0.906
31–60 days836300.76 (0.37 to 1.56)0.453
61–90 days1236301.14 (0.62 to 2.08)0.677
UnexplainedUnexposed9230 7351.000.507
Fever
15 days prevaccinationX1 18190.71 (0.26 to 1.94)
Postvaccination intervals
0–14 daysX1 17080.71 (0.26 to 1.94)0.589
15–30 days618301.06 (0.28 to 2.07)0.887
31–60 days536500.45 (0.18 to 1.10)0.079
61–90 days1236301.09 (0.60 to 1.99)0.780
  • X1 fewer than five events in each cell, data suppressed according to Clinical Practice Research Datalink policy.

  • *Unexplained fever was defined as fever not due to a known cause, for example, infection.