Objectives: We previously reported that random assignment of scientific articles to a social media exposure intervention did not have an effect on article downloads and citations. In this paper, we investigate whether longer observation time after exposure to a social media intervention has altered the previously reported results.
Methods: For articles published in the International Journal of Public Health between December 2012 and December 2014, we updated article download and citation data for a minimum of 24-month follow-up. We re-analysed the effect of social media exposure on article downloads and citations.
Results: There was no difference between intervention and control group in terms of downloads (p = 0.72) and citations (p= 0.30) for all papers and when we stratified by open access status.
Conclusions: Longer observation time did not increase the relative differences in the numbers of downloads and citations between papers in the social media intervention group and papers in the control group. Traditional impact metrics based on citations, such as impact factor, may not capture the added value of social media for scientific publications.
Keywords: Bibliometrics; Citations; Downloads; Facebook; Social media; Twitter.