Non-publication and delayed publication of randomized trials on vaccines: survey.
OBJECTIVE
To evaluate the extent of non-publication or delayed publication of registered randomized trials on vaccines, and to investigate potential determinants of delay to publication.


METHODS
Survey.


METHODS
Trials registry websites, Scopus, PubMed, Google.


METHODS
Randomized controlled trials evaluating the safety or the efficacy or immunogenicity of human papillomavirus (HPV), pandemic A/H1N1 2009 influenza, and meningococcal, pneumococcal, and rotavirus vaccines that were registered in ClinicalTrials.gov, Current Controlled Trials, WHO International Clinical Trials Registry Platform, Clinical Study Register, or Indian, Australian-New Zealand, and Chinese trial registries in 2006-12. Electronic databases were searched up to February 2014 to identify published manuscripts containing trial results. These were reviewed and classified as positive, mixed, or negative. We also reviewed the results available in ClinicalTrials.gov.


METHODS
Publication status of trial results and time from completion to publication in peer reviewed journals.


RESULTS
Cox proportional hazards regression was used to evaluate potential predictors of publication delay.


RESULTS
We analysed 384 trials (85% sponsored by industry). Of 355 trials (404,758 participants) that were completed, 176 (n=151,379) had been published in peer reviewed journals. Another 42 trials (total sample 62,765) remained unpublished but reported results in ClinicalTrials.gov. The proportion of trials published 12, 24, 36, and 48 months after completion was 12%, 29%, 53%, and 73%, respectively. Including results posted in ClinicalTrials.gov, 48 months after study completion results were available for 82% of the trials and 90% of the participants. Delay to publication between non-industry and industry sponsored trials did not differ, but non-industry sponsored trials were 4.42-fold (P=0.008) more likely to report negative or mixed findings. Negative results were reported by only 2% of the published trials.


CONCLUSIONS
Most vaccine trials are published eventually or the results posted in ClinicalTrials.gov, but delays to publication of several years are common. Actions should focus on the timely dissemination of data from vaccine trials to the public.
Department of Medicine and Aging Sciences, University of Chieti, Via dei Vestini 5 66013 Chieti, Italy CeSI Biotech, Via Colle dell'Ara, Chieti, Italy lmanzoli@post.harvard.edu.
Lamberto
L
Manzoli
Department of Medicine and Aging Sciences, University of Chieti, Via dei Vestini 5 66013 Chieti, Italy Local Health Unit of Pescara, Italy.
Maria Elena
ME
Flacco
Division of Clinical Epidemiology and Biostatistics, Institute of Social and Preventive Medicine, University of Bern, Switzerland Division of International and Environmental Health, Institute of Social and Preventive Medicine, University of Bern, Switzerland.
Maddalena
M
D'Addario
Department of Medicine and Aging Sciences, University of Chieti, Via dei Vestini 5 66013 Chieti, Italy CeSI Biotech, Via Colle dell'Ara, Chieti, Italy.
Lorenzo
L
Capasso
Department of Public Health and Infectious Diseases, Sapienza University of Rome, Italy.
Corrado
C
De Vito
Department of Public Health and Infectious Diseases, Sapienza University of Rome, Italy.
Carolina
C
Marzuillo
Department of Public Health and Infectious Diseases, Sapienza University of Rome, Italy.
Paolo
P
Villari
Stanford Prevention Research Center, Department of Medicine, Stanford University School of Medicine, Stanford, CA, USA Department of Health Research and Policy, Stanford University School of Medicine, Stanford, CA, USA.
John P A
JP
Ioannidis
D001428:Bacterial Vaccines; D015706:Bibliometrics; D016208:Databases, Factual; D006801:Humans; D011643:Publishing; D016032:Randomized Controlled Trials as Topic; D014765:Viral Vaccines
D001428:Bacterial Vaccines; D014765:Viral Vaccines