Vague language in the MMR vaccine controversy. A corpus-assisted discourse analysis of its functional use

This paper explores how vague language is used in multiple forms of specialised knowledge which have contributed to triggering the ongoing debate on MMR vaccine-induced autism. The controversy has been stirred up by the publication of the Wakefield et al. paper in 1998, considered one of the most serious cases of fraud in medical history. In the current paper, contending discourses shaped by different scientific and lay agents are considered in a diachronic perspective in order to investigate how the legitimacy of the knowledge claim is disputed through the functional use of approximators, vague quantifiers, epistemic stance markers, subjective stance markers and general extenders/placeholders. Accordingly, a corpus of various text types is introduced to disclose how fraudulent scientific knowledge is produced, propagated in the public domain as a medical myth, and refuted through investigative journalism which has led to the rare practice of retraction of the 1998 research article. A corpus-assisted approach to discourse analysis is adopted to unpack the functions these vague language categories play in this evolving process of knowledge production, reception and reconstruction, which allows new controversial interpretations of the same knowledge to emerge. Quantitative and qualitative findings shed light on how the set of vague categories functionally operate to cast doubts about scientific knowledge, and strengthen its assumptions on the divide between 'good' and 'bad science'. Ultimately, the study reveals how vague language can be artfully deployed as a covert persuasive technique to undermine public confidence in the benefits of vaccination, also by drawing on the use made of vagueness by the scientific community to express uncertainty as part of the ethical practice of advancing new knowledge claims.