Technical Barriers
Question Items	Mean (SD)**	95% CI
Data not preserved or archived.	2.96 (0.08)	[2.80-3.11]
Language - Data not recorded in a local language, limiting the possibility to integrate and use such data together with other data sets, particularly in an international context.	2.68 (0.07)	[2.54-2.82]
Technical issues - lack of software to view or process data.	2.55 (0.08)	[2.39-2.71]
Lack of metadata and standards - lack of information that describes the data, which leads to limited secondary data use.	3.21 (0.08)	[3.05-3.36]
Motivational Barriers
Question Items	Mean (SD)**	95% CI
No incentives - Data sharing requires time and resources. The benefit of data sharing is often delayed and uncertain (e.g. possibly more efficient disease control programs) instead of immediately relevant to data providers (e.g. scientific credit or training).	3.41 (0.07)	[3.27-3.55]
Opportunity cost - Researchers who have invested time and effort in data collection could anticipate that scientific credit or other opportunities may be lost if data recipients with greater capacity for analysis could gain the majority of credit.	3.22 (0.08)	[3.07-3.38]
Disagreement on data use - Data providers may disagree with the intended secondary use of their data or may consider their data inappropriate for a certain use.	3.12 (0.08)	[2.96-3.27]
Economic or Political Barriers
Question Items	Mean (SD)**	95% CI
Lack of resources - data sharing oftentimes requires human and technical resources for data preparation, annotation, communication with recipients, computer equipment, internet connectivity, etc.	3.53 (0.05)	[3.42-3.63]
Lack of trust - In the absence of trust, providers could anticipate potential misinterpretation, misuse or intentional abuse of the data.	3.33 (0.05)	[3.22-3.44]
Lack of guidelines - Frequently, official guidelines on data sharing simply do not exist, are unclear or inconsistent.	3.16 (0.07)	[3.03-3.30]
Ownership and copyright - Agencies that collect public health data are often responsible for the protection of individual and community privacy and may feel that a guardianship or ownership role is bestowed on them by the public. Copyright may be used to restrict rather than expand access to data.	3.21 (0.09)	[3.03-3.38]
Ethical Barriers
Question Items	Mean (SD)**	95% CI
Protection of Privacy - Many agencies have the mandate and authority to collect private data from the population governed by the Health Insurance Portability and Accountability Act (HIPAA) in the US or similar legislation in other countries. A clear distinction between data containing personal identifiers and fully anonymous data may not always be possible, leading to restrictive policies on all types of data due to privacy concerns.	3.22 (0.07)	[3.07-3.36]
Lack of proportionality - The issue of proportionality, the careful deliberation in assessing the risks and benefits that derive from the amount and type of data requested compared to the potential impact of its secondary use, has been identified as a guiding ethical principle for public health data sharing.	2.56 (0.09)	[2.38-2.73]
Lack of reciprocity - Data sharing practices may not always be fair, and data producers have often felt exploited in transactions where they receive little credit or benefit from their work, while data users that can rapidly analyze data and publish results benefit from academic credit and career advancement.	3.05 (0.08)	[2.90-3.21]