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. 2016 Dec 20;6(12):e011317. doi: 10.1136/bmjopen-2016-011317

Figure 1.

Figure 1

The duration of phases (first examination, second examination and follow-up periods) is shown with thick lines. Four examples of follow-up periods are shown with thin lines. Follow-up starts on a scheduled examination date; the first and the second follow-up periods do not overlap for a specific individual. MV, measles vaccine.