The interaction between barriers to data sharing in public health is complex, and single solutions to single barriers are unlikely to be successful. Political, economic and legal obstacles will be the most challenging to overcome. Public health data sharing occurs extensively as a collection of subregional and regional surveillance networks. These existing networks have often arisen as a consequence of a specific local public health crisis, and should be integrated into any global framework. Data sharing in public health is successful when a perceived need is addressed, and the social, political and cultural context is taken into account. A global data sharing legal framework is unlikely to be successful. A global data governance or ethical framework, supplemented by local memoranda of understanding that take into account the local context, is more likely to succeed. The International Health Regulations (IHR) should be considered as an infrastructure for data sharing. However, their lack of enforcement mechanism, lack of minimum data sets, lack of capacity assessment mechanism, and potential impact on trade and travel following data sharing need to be addressed. Optimal data sharing does not equate with open access for public health data.