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Open Access

Peer-reviewed

Research Article

Quantifying the effect of Wakefield et al. (1998) on skepticism about MMR vaccine condom in the U.Due south.

• Dominik Stecula

Quantifying the effect of Wakefield et al. (1998) on skepticism about MMR vaccine rubber in the U.S.

• Matthew Motta,
• Dominik Stecula

ten

• Published: August nineteen, 2021
• https://doi.org/ten.1371/periodical.pone.0256395

Figures

Abstruse

Background

Efforts to trace the rise of childhood vaccine condom concerns in the US often propose Andrew Wakefield and colleagues' retracted 1998 Lancet written report (AW98)–which alleged that the MMR vaccine tin crusade children to develop autism–as a primary cause of The states vaccine skepticism. Even so, a lack of public opinion information on MMR prophylactic collected before/after AW98'due south publication obscures whether anecdotal accounts are indicative of a potentially-causal outcome.

Methods

We address this problem using a regression discontinuity framework to study alter in monthly MMR injury claims (N = 74,850; from 1990–2019) from the Vaccine Adverse Events Reporting System (VAERS) to proxy business organization virtually vaccine condom. Additionally, we advise a potential machinery for the effect of AW98 on vaccine skepticism, via automated sentiment analyses of MMR-related news stories (N = 674; from 1996–2000) in major tv and newspaper outlets.

Results

AW98 led to an immediate increase of nigh 70 MMR injury claims cases per calendar month, averaging across six estimation strategies (meta-analytic effect = 70.44 [52.19, 88.75], p < 0.01). Preliminary evidence suggests that the volume of negative media attending to MMR increased in the weeks following AW98's publication, across iv interpretation strategies (meta-analytic outcome = 9.59% [3.66, 15.51], p < 0.01).

Conclusions

Vaccine skepticism increased following the publication of AW98, which was potentially fabricated possible by increased negative media coverage of MMR.

Significance

Childhood vaccine skepticism presents an important challenge to widespread vaccine uptake, and undermines support for pro-vaccine health policies. In improver to advancing our understanding of the previously-obscured origins of US vaccine skepticism, our piece of work cautions that loftier-profile media attention to inaccurate scientific studies can undermine public confidence in vaccines. We conclude by offering several recommendations that researchers and wellness communicators might consider to find and address future threats to vaccine conviction.

Commendation: Motta M, Stecula D (2021) Quantifying the result of Wakefield et al. (1998) on skepticism about MMR vaccine safety in the U.South. PLoS I xvi(8): e0256395. https://doi.org/10.1371/journal.pone.0256395

Editor: Sergio A. Useche, Universitat de Valencia, Espana

Received: January 26, 2021; Accustomed: July 27, 2021; Published: August 19, 2021

Copyright: © 2021 Motta, Stecula. This is an open up access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in whatsoever medium, provided the original author and source are credited.

Data Availability: All data and syntax files are available from the OSF database at the following URL: https://osf.io/n7z2v/.

Funding: The author(s) received no specific funding for this work.

Competing interests: The authors have alleged that no competing interests exist.

Introduction

In late Feb 1998, a enquiry team led by Andrew Wakefield published an article in The Lancet suggesting a link between the Measles, Mumps, and Rubella vaccine (MMR) and the evolution of autism in children. An investigation into the study (hereafter, AW98), conducted more than ten years afterwards its original publication date, ended that the article'south data did not support this claim, and documented credible show of research malfeasance [1].

Although the slice was eventually retracted in Spring 2010 [1], both scholarly [2–4] and journalistic [5] efforts to identify the origins of gimmicky vaccine skepticism in the U.S. suggest that the publication of AW98— and early on media attention to information technology—was a pivotal moment (and perhaps the pivotal moment) in the mainstream acceptance of skepticism about MMR vaccine condom. Today, approximately one in 3 Americans believes that childhood vaccines can cause children to develop autism [6].

Studies attributing the rise in childhood vaccine skepticism to AW98, still, rely primarily on anecdotal testify [2, 4–5]. This may be due in function to the scarcity of polling information about MMR safe in the immediate backwash of AW98, and the virtual absence of such data prior to 1998 [7]. I mode that scholars accept circumvented this business concern is by investigating the issue of AW98 on childhood vaccine skepticism is to assess whether or non MMR refusals (presumably resulting from safety concerns) increased in the aftermath [three]. Using this approach, AW98—and media coverage of information technology—appears to have had a curt-lived and express influence on vaccine refusal rates.

However, as outright MMR refusal is an extreme form of action—complicated by the fact that taking parents may exist required to seek medical or philosophical exemptions to immunization statutes [8]—it may lack the sensitivity necessary to detect broader changes in public opinion toward MMR. In this study, make use of a comparatively more-sensitive indicator of MMR skepticism; parent reports of negative reactions to the MMR vaccine from the Vaccine Adverse Events Reporting Arrangement (VAERS; Department of Health & Human Services). These reports enable parents to express skepticism near MMR safety by reporting potential side effects their children may have experienced; significant that parents demand non accept the more-extreme step of refusing vaccines outright to annals concerns about its condom.

If VAERS reports are sufficiently-sensitive indicators of MMR skepticism, and if conventional wisdom nigh AW98 is right, we should await to meet a sharp increase in reports following the publication of—and media attention to—the debunked written report. While VAERS reports, dissimilar public opinion surveys, cannot tell united states of america the "base rate" of MMR skeptical views in the mass public, they tin at least offer insights into whether or not the levels of skepticism necessary to aspect MMR to various potential side effects following AW98.

Empirically demonstrating whether or non AW98 "moved the needle" on vaccine skepticism is an important empirical task, as it can assist scholars better understand how communication surrounding debunked or misleading science might become on to shape behaviors relevant to public health. Additionally, given the link between MMR skepticism and opposition to policies that encourage vaccination [7, 9], this research can aid us understand the potential long-run impacts of attention to fraudulent scientific claims on support for public wellness policies.

Materials & methods

Written report design, population, and setting

Information from this study come from two sources. First, we test whether or not business organisation almost MMR safety increased following the publication of AW98 using publicly bachelor information of reports of adverse reactions to the MMR vaccine, via the Section of Health and Homo Services (DHHS) Vaccine Adverse Event Reporting System (VAERS) [ten]. Doctors and other vaccine providers report potential adverse events to VAERS in consultation with the parents of children administered the MMR vaccine.

Next, we provide supplemental tests of whether or non media coverage of AW98 presents a plausible mechanism for the effects documented in Fig one. Nosotros obtained data from Lexis Nexis Academic past searching for news stories referencing "measles" or "MMR" in national tv set broadcasts (ABC, CBS, PBS, and NBC News) and high-apportionment newspapers (U.s. Today, Washington Post, and the New York Times, Associated Press). Nosotros measured story sentiment using Linguistic Research and Word Count (LIWC) software [eleven], which computes the ratio of negatively to positively valenced words in each story, standardized on a calibration ranging from 0 (most negative) to 100 (near positive).

Fig i. MMR VAERS reports pre/post AW98.

Panel a presents yearly MMR VAERS reports before/afterward the publication of AW98 (dashed vertical line). Panel b presents RD estimates of the issue (B) and two-tailed significance (p) of AW98 on weekly report counts before/later on AW98 (dashed vertical line), across several RD estimation strategies (come across: Materials & Methods). All RD estimates are calculated every bit linear effects; which is advisable given the loftier caste of consonance between the locally weighted polynomial trend line (dashed lines) and linear trend line (solid line) fit to the monthly data.

https://doi.org/x.1371/periodical.pone.0256395.g001

Outcome measures

Our mensurate of MMR safety concerns is a count of all monthly MMR event reports filed to VAERS from 1990 (when the program was created) to 2019. Annotation that while several varieties of MMR are in use today (e.g., MMRV, which includes varicella), we focus on only MMR; both considering it was the subject of AW98, and because information technology is consistently available throughout the series.

Additionally, for our supplemental tests, negative news book about the MMR vaccine is the boilerplate (mean) negativity score for all MMR-related stories produced each week from March 1996 (2 years before AW98's publication) to March 2000 (two years post). We weighted weekly averages past the total number of stories featured in that week.

Statistical assay

To test whether or not AW98 had a causal upshot on increased MMR condom concerns, nosotros starting time compare the number of MMR reports filed to VAERS pre/postal service-AW98 using a regression discontinuity (RD) setup. For robustness, nosotros present several versions of the RD results that vary (1) whether the RD is "sharp" (estimated before/later the date AW98 was published) or "fuzzy" (within a month of the paper's publication); (ii) written report assemblage level (monthly, quarterly, yearly, or using an automatic "bin" selection method via a coverage error rate [CER] optimal bandwidth estimator); (3) population adjusted vs. non-adjusted effect size estimators (to ensure that a potential increase in reports is not the result of population growth over fourth dimension), and (4) the use of bias-correction standard error estimates. Results of all models are presented in Fig 1. All data and code necessary to replicate these analyses, as well every bit the placebo tests referenced in a higher place, can be found at: https://osf.io/n7z2v/.

To detect whether or not media coverage of AW98 might be responsible for increased MMR concern, we again use an RD setup; this time aggregating both the volume and tone of MMR stories from two years earlier and after the publication of AW98 (1996–2000). These tests, visualizations, and the fourth dimension demarcations are synthetic identically to those reported in Fig i —modeling modify in sentiment over time—with the exception that: (ane) we restrict information aggregation to be at the weekly level (as monthly aggregations would leave the model nether-powered; daily aggregations would accept 'sparse' days with no coverage); (two) all models include story counts as a covariate (as we are interested in account for the volume of negative coverage); and, (3) both the locally weighted and linear trend lines adjust for weekly story book.

In both cases, we summarize the results of these estimation procedures with a formal meta-analysis, using Cohen'due south standardized mean difference process. Annotation that we report these quantities at only the monthly level for the adverse events data. This serves equally a conservative estimate of the outcome of AW98 on vaccine skepticism, as reporting the larger aggregation periods (included as robustness checks) would potentially inflate the average effect size.

Results

Fig 1 presents an initial examination of AW98's effect on MMR safety concerns. For reference, panel a presents the full yearly count of reported adverse experiences with MMR, from 1990 to 2019. Panel b visualizes the results of several regression discontinuity (RD) estimates of both the substantive consequence of AW98 on monthly VAERS reports and statistical significance. If AW98 did indeed influence public perceptions of MMR vaccine safe, would nosotros expect to see a substantively large and statistically significant increase in the flow post-obit the newspaper'south publication, compared to the period before it.

The descriptive results presented in Fig 1A document that, prior to the publication of AW98, parents typically reported nether 2,000 adverse MMR events per twelvemonth. Post-obit AW98, that quantity steeply grew to over four,000 yearly reports by 2004. Formal RD tests presented in Fig 2B certificate a big and statistically significant increment in events immediately following the publication of AW98. Meta-analyzing the six monthly tests presented in the effigy suggests an increase of lxx.44 [52.19, 88.75] reports per week.

Fig 2. MMR news sentiment pre/post AW98 (weighted by volume).

Figure presents weekly sentiment ratings of vaccine-related stories from major news outlets (gray shaded circles), weighted by the total amount of stories published that week (larger when there is more coverage in a given week). The figure too reports the effect (B) and two-tailed significance (p) of AW98 on weekly report counts before/after AW98 (dashed vertical line), across several RD estimation strategies (encounter: Materials & Methods). All RD estimates are calculated as linear furnishings; which is appropriate given the high degree of consonance betwixt the locally weighted polynomial trend line (dashed lines) and linear trend line (solid line) fit to the weekly information; both of which adjust for total book. N = 674 stories.

https://doi.org/10.1371/journal.pone.0256395.g002

These results hold across tests that vary both the written report aggregation period, standard mistake estimator, and whether AW98 is treated as a "sharp" or "fuzzy" discontinuity. The results also agree when bookkeeping for population growth over time (which might upshot in more reports being filed).

Additionally, to ensure that growth MMR concern is non confounded past (1) changes in the procedures by which parents report agin furnishings to VAERS over fourth dimension (e.yard., the power to submit reports online as personal home computing and internet admission grew over time), (2) changes in how health care providers diagnose autism, and/or (3) time itself–i.e., the possibility that attitudes toward all vaccines grew more than negative over time for reasons unrelated to AW98 –we offer a placebo exam using reports of adverse reactions to HIBV (Haemophilus Influenzae Type B Vaccine)–which has been routinely administered to children since the early 1990s, simply was not identified as a wellness risk in AW98 –in the online materials.

If the effects of AW98 were to coincide with unobserved changes in reporting mechanisms and/or more general changes in public vaccine sentiment, we should discover comparatively more VAERS reports in the post (vs. pre) AW98 period for the HIBV placebo. This would be indicative of a spurious effect of AW98. Nevertheless, the analyses presented in the online materials advise that AW98 had no statistically or substantively discernable effect on HIBV agin event reports (see: S1 Fig).

Fig ii presents evidence of a potential mechanism for this effect. In the weeks following AW98'due south publication, the volume of negative news stories near the MMR vaccine from major news outlets increased substantially. Meta-analyzing the RD analyses presented in Fig 2 suggests that negativity increased by 9.59% [3.66, 15.51] following publication, approaching conventional two-tailed significance in three out of four interpretation strategies. This provides preliminary evidence that AW98 influenced how the media talked well-nigh MMR, which in turn drew public attention to concerns nigh vaccine safety.

Conclusions

This inquiry demonstrates that AW98, and media attention to it, may take changed how some Americans viewed MMR safety. Whereas anecdotal accounts suggest that AW98 led to an increase in vaccine skepticism in the US, early on studies of pre/mail AW98 vaccine compliance rates cast doubt on the report's affect on public opinion. By constructing more sensitive indicators of vaccine skepticism, we notice a large, robust, and statistically significant uptick in public concern about MMR condom following AW98.

Without public opinion data, of course, we cannot determine precisely how many Americans came to hold negative views toward MMR postal service-AW98. However, our approach allows us to document modify in vaccine sentiment over time attributable to AW98; enabling us to shed new lite on a previously-muddled surface area of vaccine history.

Discussion

Many Americans concur skeptical views about the safety of childhood vaccines [7, ix, 12–15]. Vaccine skepticism has important public health consequences, as people who believe that vaccines are unsafe tend to be less likely to intend to vaccinate themselves and their children against vaccine-preventable illnesses [14–16], and more than likely to oppose pro-vaccine wellness policies [vii, 17]. Understanding the origins of vaccine skepticism in the U.S. can help researchers amend preempt how to mitigate the outcome that fraudulent claims might have on public vaccine opinion in the future [18].

Consequently, this enquiry has several important public health consequences. First, it suggests that attention to false or misleading vaccine enquiry can impact public confidence in vaccines. Media sources should therefore piece of work in consultation with researchers to stringently vet vaccine-related stories earlier sharing their results with the public. This will be particularly of import in a post COVID-xix pandemic public health environment, where scholars take the opportunity to produce research on the (potential) long-term side effects of vaccines currently approved for public use.

Additionally, our work underscores the importance of conducting regular public opinion polling well-nigh vaccine safety; even before the possibility of controversy. While VAERS is a useful mode to detect change in vaccine attitudes in the absence of public stance data, surveys enable us to more-precisely certificate modify in vaccine skepticism, over fourth dimension. Constant surveillance of vaccine opinion can aid researchers better understand how changes in the media environment might influence public vaccine confidence, and (potentially) thereby influence related vaccine policy attitudes and health behaviors.

Finally, our work suggests several opportunities for futurity research. For example, our written report cannot disentangle the precise mechanism by which AW98 media coverage might influence public vaccine attitudes. Media attention could, for case, directly influence how Americans feel about vaccination past cartoon parents' attentions to the possibility that their children experience adverse side effects from vaccination. Alternatively, the vaccine media environs could indirectly influence vaccine attitudes by changing health care professionals attentiveness to potential side effects (due east.g., increased monitoring for autism symptoms [19]), and thereby engender concern among parents resulting in increased VAERS reports. Efforts to uncrease direct from more-complex causal accounts are a worthwhile endeavor in previous inquiry.

Additionally, and mayhap about importantly, our enquiry offers an opportunity to learn more well-nigh the effects of COVID-nineteen vaccine media coverage on attitudes toward vaccination. As more Americans became eligible to vaccinate against the virus, vaccine skeptics and prominent media figures who held skeptical views toward vaccination sometimes made employ of VAERS reports to justify their (often, misinterpreted) concerns about COVID-19 vaccine safety [20–22]. Consequently, time to come work should make an effort to determine whether or not media coverage of these issues in turn influenced reports to VAERS. This information can help scholars to not only ameliorate sympathise the furnishings of media coverage on vaccine attitudes, in awarding to diseases not studied in our work, but how the quality of adverse issue data reported to VAERS might be influenced by exogenous media, political, and other social events.

Moreover, although public stance data about COVID-19 vaccine attitudes and behaviors is comparatively more than plentiful than MMR opinion data, few surveys inquire uptake questions at the daily level. Every bit nosotros demonstrate in this research, VAERS information–which can be readily aggregated at the daily level –could function as a useful supplement for public stance data to find brusque-term effects of changes in the vaccine communication surround. For example, researchers could apply VAERS data to certificate the furnishings of media attention the federal authorities's decision to temporarily pause administration of Johnson & Johnson'due south COVID-nineteen vaccine. Because this interruption lasted but ten days [23], VAERS data may offering an opportunity to assess these furnishings with additional granularity.

Supporting information

S1 Fig. Placebo Test: HIBV adverse effect reports.

Placebo examination replicates the analyses and tests presented in Fig 1 in the principal text (although note that these analyses also business relationship for exponential decline in VAERS reports following the publication of AW98 in the bias correction RD models by specifying a quadratic regression estimator). Please refer to the chief text for additional methodological details. HIBV refers to the Haemophilus Influenzae Type B Vaccine, which–while typically administered in childhood since the early 1990s, similar MMR—was not mentioned every bit a potential cause of autism in the AW98 paper. Consequently, if the effects documented in Fig 1 are merely the result of unobserved confounds, or time itself, we would look to meet a corresponding spike in adverse upshot reports following the publication of AW98. Consistent with the thought that the effects of AW98 are non confounded, the results certificate little effect of AW98 on VAERS reports for HIBV. Visually, although adverse event reports rise slightly following the publication of AW98, reports (1) were already increasing prior to its publication, and (2) had been in a period of exponential decline earlier 1998. Statistically, the results fail to document a significant increase in VAERS reports after correcting for the (pronounced) inverted parabolic nature of the pre-AW98 data, using quadratic regression. Note that because the analyses both substantively and statistically certificate no show of a discontinuity in adverse reports post-obit AW98 in college-powered (weekly) analyses, we do not re-guess at the yearly or quarterly level.

https://doi.org/ten.1371/journal.pone.0256395.s001

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