Table 2. Examples of research questions for the three research domains.

Research Domain	Research Question*	Reference
Operational	Can the “communication for behavioural impact” (COMBI) strategy improve the poor compliance with mass drug administration for LF elimination in Tamil Nadu, India?	[46],[47]
	Which locations should be targeted for delivering HIV prevention services in Kawempe district, Uganda?	[9]
	Which of the current ART payment strategies in use in Nairobi should be retained for the new integrated programme?	[48]
	Should the sleeping sickness programme in Equator Nord province, DRC, change its first-line drug?	[49]
Implementation	How to deliver ivermectin for onchocerciasis control and ensure sustained high treatment coverage in isolated rural communities?	[50]
	How to improve access to vaccination among children who are currently not reached by immunisation services?	[25]
	How to implement antenatal syphilis screening—one-stop versus conventional service?	[51]
	How to effectively implement a new intervention package for kala azar elimination in the Indian subcontinent?	[52]
Health system	To what extent do health services reach the poor? How can this be improved?	[32]
	Should fees be charged to clients who use health centres for curative services?	[17]
	How effective are different policies for attracting nurses to rural areas?	[53]
	What has been the impact of the rapid scale-up of HIV programmes on fragile health systems?	[54]

*As noted above, depending on how the question is phrased and the research is designed; some of these questions can be addressed in several research domains.