Strengths and Limitations
In addition to the wavier of consent and RCT design, the strengths of our trial included high follow-up rates and clinician-level elements that can be implemented by most health care services. A trial limitation was the inability to implement an additional nudge in the form of a reminder letter to GPs (primary care–level nudge). This was because of software that was unable to extract GP details for each patient in order for us to send reminder letters. This is an important consideration given the key role that GPs play in primary care. Additionally, the absence of a third trial arm to compare the effect of nudging patients directly (ie, without the clinician-level nudge) would have provided useful data for health systems where direct nudging of patients would be required. The research team had limited information on the parents (as nudge recipients) due to the nature of the nudge and waiver of consent; this information may have aided interpretation and identified who the nudge benefited most.