Table 2.

Association between inactivated influenza vaccine, vasculitis and unexplained fever*

Outcome	Risk period	Events (n)	Person-time (days)	Incidence rate ratio (95% CI)	P values
Vasculitis	Unexposed	89	30 936	1.00	0.906
	15 days prevaccination	5	1815	0.95 (0.38 to 2.33)
	Postvaccination intervals
	0–14 days	X1	1694	0.41 (0.10 to 1.65)	0.207
	15–30 days	5	1815	0.95 (0.38 to 2.33)	0.906
	31–60 days	8	3630	0.76 (0.37 to 1.56)	0.453
	61–90 days	12	3630	1.14 (0.62 to 2.08)	0.677
Unexplained	Unexposed	92	30 735	1.00	0.507
Fever	15 days prevaccination	X1	1819	0.71 (0.26 to 1.94)
	Postvaccination intervals
	0–14 days	X1	1708	0.71 (0.26 to 1.94)	0.589
	15–30 days	6	1830	1.06 (0.28 to 2.07)	0.887
	31–60 days	5	3650	0.45 (0.18 to 1.10)	0.079
	61–90 days	12	3630	1.09 (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.