User-Driven Comments on a Facebook Advertisement Recruiting Canadian Parents in a Study on Immunization: Content Analysis

Jordan Lee Tustin   ^{1, 2} , MHSc, PhD ;   Natasha Sarah Crowcroft   ^{2, 3, 4} , MA (Cantab), MD, PhD, FFPH ;   Dionne Gesink   ² , MSc, PhD ;   Ian Johnson   ² , MSc, MD, FRCPC ;   Jennifer Keelan   ⁵ , MA, PhD ;   Barbara Lachapelle   ⁶ , MASc

¹ School of Occupational and Public Health, Ryerson University, Toronto, ON, Canada

² Dalla Lana School of Public Health, University of Toronto, Toronto, ON, Canada

³ Public Health Ontario, Toronto, ON, Canada

⁴ Laboratory Medicine and Pathobiology, University of Toronto, Toronto, ON, Canada

⁵ Department of Public Health, Concordia University of Edmonton, Edmonton, AB, Canada

⁶ Toronto Public Health, Toronto, ON, Canada