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. Author manuscript; available in PMC: 2013 Nov 1.
Published in final edited form as: Ann Epidemiol. 2012 Oct 5;22(11):799–806. doi: 10.1016/j.annepidem.2012.09.003

Table 3.

Hazard ratio (HR) of influenza vaccination during pregnancy on the risk of preterm birth in conventional analysis (with 95% confidence interval [CI]) and bias-corrected analysis (with 95% simulation interval [SI]).

Preterm Unadjusted 95% CI/SI Adjusted 95% CI/SI
Model Exposure n % n % HR HRa
Whole population 2267 100.0 163 7.2
Conventional No influenza vaccination during pregnancy 1549 68.3 110 7.1 Reference
Any influenza vaccination during pregnancy 718 31.7 53 7.4 1.11b 0.80, 1.54 1.00 0.71, 1.41
Bias-corrected No influenza vaccination during pregnancy 1574 69.4 111 7.1 Reference
Any influenza vaccination during pregnancy 693 30.6 52 7.5 1.12 0.78, 1.61 1.04 0.70, 1.52
a

Adjusted for maternal race, age, infertility treatment, illicit drug use, study center and multifetal gestation

b

Unadjusted odds ratio: 1.04 [0.74, 1.47]; unadjusted time-invariant HR: 1.03 [0.75, 1.44]