Access to data from all trials

An official Cochrane policy. Last updated April 2013.

Cochrane Supports Access to Data from All Trials

Cochrane is committed globally to providing policy-makers, clinicians, patients and their caregivers with up-to-date and accurate information about the effectiveness and safety of healthcare interventions. It publishes systematic reviews in The Cochrane Library and updates these regularly.

Cochrane systematic reviews draw heavily on the results from randomised and non-randomised controlled trials. Because trial results are often selectively reported, the benefits of interventions can be exaggerated and the harms underestimated. To be able to summarize the effectiveness and safety of healthcare interventions, we need to know what trials were done, how they were conducted and what their findings were.1 The public sharing of information about trial results will allow them to be assessed both individually and in the context of systematic reviews.

To ensure that data from all trials evaluating the effects of healthcare interventions become publicly available, without undue delay, Cochrane calls for:

  • All trials to be registered before recruitment of the first participant on a publicly accessible database (see the Cochrane statement on this here);
  • Full trial protocols to become publicly available free of charge and in easily accessible electronic formats, preferably at inception, but certainly before study recruitment has completed. Any changes to the protocol should be clearly documented and dated;
  • Summary results for all protocol-specified outcomes, with analyses based on all participants, to become publicly available free of charge and in easily accessible electronic formats within 12 months after completion of planned collection of trial data;
  • Raw, anonymised, individual participant data to be made available free of charge; with appropriate safeguards to ensure ethical and scientific integrity and standards, and to protect participant privacy (for example through a central repository, and accompanied by suitably detailed explanation);
  • Government agencies to recognise collective responsibility for trial data, including  sponsors, investigators, research ethics committees, trial participants and the wider public, and therefore to ensure that adequate mechanisms, resources and infrastructure are provided to facilitate access to the data, protocols and results;
  • Government agencies to consider introducing legislation that makes it a requirement to  provide the results from all trials to the public;

Calls for data sharing have also come from a variety of international organisations, research funders, and others, including the Organisation for Economic Co-operation and Development (OECD),2,3 the World Health Organization (WHO), the US National Institutes of Health (NIH), the Bill and Melinda Gates Foundation and the Hewlett Foundation,4 the US Congress,5 the European Commission,6,7 the European Ombudsman,8,9 journal editors,10,11,12,13,14 the UK Medical Research Council (MRC),15 and the Wellcome Trust.16 Such calls have mostly been restricted to publicly-funded research, but the distinction between publicly-funded research and industry-funded research is an artificial one, as the interests of the patients and the wider public should override commercial interests.8,9

Cochrane is a partner of the AllTrials campaign which has brought together individuals and organisations from across the world in support of promoting full disclosure of summary results from trials. Cochrane supports the use of individual participant data in systematic reviews and contributes to the ongoing debate around how such data should be shared and re-used.17


  1. Antes G, Chalmers I. Under-reporting of clinical trials is unethical. Lancet 2004;361:978.
  2. OECD. Science, Technology and Innovation for the 21st Century. Meeting of the OECD Committee for Scientific and Technological Policy at Ministerial Level, 29-30 January 2004 – Final Communiqué. 30/01/2004.,3343,en_2649_201185_25998799_1_1_1_1,00.html (accessed 18 June 2013).
  3. Arzberger P, Schroeder P, Beaulieu A, et al. Promoting access to public research data for scientific, economic, and social development. Data Science Journal 2004;3:135–52.
  4. Wellcome Trust. Sharing research data to improve public health: full joint statement by funders of health research. 10 January 2011. (accessed 18 June 2013).
  5. U.S Department of Health and Human Services. National Institutes of Health Public Access. (accessed 18 June 2013).
  6. Commission of the European Communities. Communication from the Commission to the Council, the European Parliament, the European Economic and Social Committee. On scientific information in the digital age. Access, dissemination and preservation. 2007. (accessed 18 June 2013).
  7. Commission of the European Communities. Communication from the Commission – Guidance on the information concerning paediatric clinical trials to be entered into the EU Database on Clinical Trials (EudraCT) and on the information to be made public by the European Medicines Agency (EMEA), in accordance with Article 41 of Regulation (EC) No. 1901/2006. 4 February 2009. (accessed 18 June 2013).
  8. Gøtzsche PC, Jørgensen AW. Opening up data at the European Medicines Agency. BMJ 2011;342:d2686.
  9. Gøtzsche PC. Why we need easy access to all data from all clinical trials and how to accomplish it. Trials 2011;12(1):249.
  10. General Information for Authors. Science. (accessed 18 June 2013).
  11. Information for Authors. Lancet August 2011. (accessed 18 June 2013).
  12. Groves T. Managing UK research data for future use. BMJ 2009;338:b1252.
  13. PLoS One. PLoS Medicine Editorial and Publishing Policies. Sharing of Materials, Methods and Data. (accessed 18 June 2013).
  14. Gøtzsche PC. We need access to all data from all clinical trials [editorial]. The Cochrane Library 2011 (5 Oct). (accessed 18 June 2013).
  15. Medical Research Council. MRC policy on data sharing and preservation. 2011. (accessed 18 June 2013).
  16. Wellcome Trust. Policy on data management and sharing. (accessed 18 June 2013).