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. Author manuscript; available in PMC: 2018 Dec 19.
Published in final edited form as: Vaccine. 2017 Nov 13;35(52):7297–7301. doi: 10.1016/j.vaccine.2017.10.107

Figure 1. Directed acyclic graph of influenza vaccine studies with a covariate.

Figure 1

X=health awareness (unobserved), V=vaccination status, Y=ARI status, M=seeking medical care for ARI, T=influenza test result.