Table 2.

Adjusted Cox proportional hazards model of relative hazard of acute respiratory illness (ARI) in the post-vaccination risk period compared with unvaccinated interval and vaccinated interval during 2013–2016 influenza seasons.

	Adjusted Hazard Ratio (95% Confidence Interval)
Time-varying exposure comparison	2013–2014	2014–2015	2015–2016	2013–2016 Combined
	Influenza
14-day post-vaccination vs. unvaccinateda	0.74 (0.1, 5.48)	Estimate unreliable	1.49 (0.19, 12.03)	0.63 (0.16, 2.60)
14-day post-vaccination vs. vaccinatedb	0.79 (0.1, 6.29)	Estimate unreliable	2.26 (0.25, 20.82)	0.66 (0.16, 2.84)
Vaccinatedb vs. unvaccinateda	0.94 (0.46, 1.93)	1.34 (0.59, 3.01)	0.66 (0.26, 1.69)	0.96 (0.6, 1.52)
	Non-influenza respiratory pathogen
14-day post-vaccination vs. unvaccinateda	1.03 (0.49, 2.21)	1.94 (1.08, 3.48)	2.09 (1.12, 3.88)	1.65 (1.14, 2.38)
14-day post-vaccination vs. vaccinatedb	0.53 (0.24, 1.14)	1.72 (0.91, 3.27)	1.66 (0.85, 3.23)	1.13 (0.77, 1.68)
Vaccinatedb vs. unvaccinateda	1.97 (1.39, 2.8)	1.12 (0.78, 1.62)	1.26 (0.86, 1.87)	1.44 (1.17, 1.77)
	Symptoms without pathogen detected
2-day post-vaccination vs. unvaccinateda	1.8 (0.24, 13.51)	2.44 (0.6, 10.02)	0.17 (0.01, 32.41)	1.3 (0.42, 4.08)
2-day post-vaccination vs. vaccinatedb	0.82 (0.1, 7.43)	1.56 (0.38, 6.47)	0.13 (0.01, 48.53)	1.03 (0.33, 3.24)
Vaccinatedb vs. unvaccinateda	1.23 (0.79, 1.92)	1.56 (1.12, 2.17)	1.02 (0.71, 1.48)	1.27 (1.02, 1.59)

All models adjusted for age, gender, chronic respiratory condition, and autumn, winter, spring season.

Statistically significant estimates are in bold text.

^aUnvaccinated exposure status includes individuals prior to vaccination and those who did not receive the vaccine.

^bVaccinated exposure status includes individuals after the relevant post-vaccination risk period (14-day or 2-day depending on the model).