http://www.jmir.org/2005/2/e17/

Vaccine Criticism on the World Wide Web

Richard K Zimmerman1,2, MD, MPH; Robert M Wolfe3, MD; Dwight E Fox1,
DMD; Jake R Fox1, MA; Mary Patricia Nowalk1, PhD, RD; Judith A Troy1,
MS; Lisa K Sharp3, PhD

1Department of Family Medicine and Clinical Epidemiology, University
of Pittsburgh School of Medicine, Pittsburgh, PA, USA
2Department of Behavioral and Community Health Sciences, University of
Pittsburgh Graduate School of Public Health, Pittsburgh, PA, USA
3Department of Family Medicine, Feinberg School of Medicine,
Northwestern University, Chicago, IL, USA

Corresponding Author:

Richard K Zimmerman, MD, MPH

Department of Family Medicine and Clinical Epidemiology
University of Pittsburgh School of Medicine
3518 5th Avenue
Pittsburgh, PA 15261
USA
Phone: +1 412 383 2354
Fax: +1 412 383 2306
Email: zimmer [at] pitt.edu

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ABSTRACT
Background: The incidence of vaccine-preventable diseases is directly
related to the number of unvaccinated children. Parents who refuse
vaccination of their children frequently express concerns about
vaccine safety. The Internet can influence perceptions about vaccines
because it is the fastest growing source of consumer health
information. However, few studies have analyzed vaccine criticism on
the Web.
Objective: The purposes of this paper are to examine vaccine criticism
on the Internet and to analyze the websites in order to identify
common characteristics and ethical allegations.
Methods: A structured Web search was conducted for the terms
“vaccine,” “vaccination,” “vaccinate,” and “anti-vaccination” using a
metasearch program that incorporated 8 search engines. This yielded
1138 Web pages representing 750 sites. Two researchers reviewed the
sites for inclusion/exclusion criteria, resulting in 78 vaccine-
critical sites, which were then abstracted for design, content, and
allegations.
Results: The most common characteristic of vaccine-critical websites
was the inclusion of statements linking vaccinations with specific
adverse reactions, especially idiopathic chronic diseases such as
multiple sclerosis, autism, and diabetes. Other common attributes (≥
70% of websites) were links to other vaccine-critical websites;
charges that vaccines contain contaminants, mercury, or “hot lots”
that cause adverse events; claims that vaccines provide only temporary
protection and that the diseases prevented are mild; appeals for
responsible parenting through education and resisting the
establishment; allegations of conspiracies and cover-ups to hide the
truth about vaccine safety; and charges that civil liberties are
violated through mandatory vaccination.
Conclusions: Vaccine-critical websites frequently make serious
allegations. With the burgeoning of the Internet as a health
information source, an undiscerning or incompletely educated public
may accept these claims and refuse vaccination of their children. As
this occurs, the incidence of vaccine-preventable diseases can be
expected to rise.

(J Med Internet Res 2005;7(2):e17)
doi:10.2196/jmir.7.2.e17

KEYWORDS

Vaccines; Internet; immunization; vaccine safety; vaccine criticism;
anti-vaccine

Introduction

The number of unvaccinated children is rising in the United States;
the estimated number of unvaccinated children aged 19 to 35 months
increased from 14719 in 1995 to 24073 in 2000 [1]. The number of
unvaccinated children plays an important role in the incidence of
vaccine-preventable diseases. For example, the frequency of abstainers
from vaccination has been associated with the incidence of measles and
pertussis among both vaccinated and unvaccinated children [2].

Parental Concerns About Vaccine Safety
A number of studies have documented parental concerns about vaccine
safety [1,3-5]. A 2004 online survey showed that half of parents are
concerned that a child might develop a long-term medical condition as
a result of vaccination [6]. One tenth of parents are uncomfortable
having their child vaccinated due to health concerns [6]. Another US
national survey found that the majority of parents of young children
support the use of immunization, but about one quarter are concerned
that children receive more vaccines than are good for them, and that,
as a result, their immune systems could be weakened [7]. About one
fifth (19%) do not think vaccines are proven safe prior to use in the
United States [7]. A third study comparing responses from parents of
unvaccinated versus vaccinated children found that parents of the
unvaccinated were significantly more likely to ask that their child
not be vaccinated, to believe that the MMR (measles, mumps, rubella)
vaccine causes autism, to be concerned about side effects, and to
believe that children receive too many vaccines [4]. In Colorado, the
percentage of children with philosophical exemptions to immunization
increased from 1.02% to 1.87% from 1987 to 1998 [2]. Thus, many
parents are concerned about vaccine safety, and a growing number are
expressing this by refusing vaccination of their children.

The media, both print and electronic, are frequently used to educate
the public about health issues. Similarly, the media have been used to
discourage uptake of known public health measures such as vaccination.
For example, an international study examined anti-vaccine campaigns in
the media, pertussis vaccine coverage, and disease incidence in the
United States and several European countries [8]. Those countries with
concerted anti-vaccine campaigns as reported in contemporary news
stories had significantly higher incidence of pertussis compared with
countries with few or no media reports on alleged vaccine adverse
events. The latter countries, in general, maintained high vaccination
levels with low disease incidence.

Influence of the Internet and Purpose to Study Vaccine-Critical
Websites
The Internet, the newest electronic news medium, has the potential to
influence perceptions about vaccines because it is the fastest growing
source of consumer health information. In fact, most (67%) US adults
use the Internet, and of these, 40% to 80% use it to access health
information [9-11]. With the rapid expansion of the Internet (an
estimated 19000 websites in 1995 to 36 million websites in 2001[12])
and the increasing number of people seeking health information on the
Web (an estimated 110 million adults[10]), frequent updates of the
health information being disseminated via the Internet are necessary.

The vaccine criticism movement has taken advantage of the Internet and
its ability to reach parents seeking information on vaccines and
vaccine safety. Parents can find this information with just a few key
strokes. Three studies, conducted from 1999 to 2001, provide some
insight into the vaccine criticism movement on the Internet,
describing the content and design attributes of “anti-vaccination”
websites [13-15]. The purpose of this paper is to more broadly examine
vaccine criticism on the Internet in 2004 and update previous
findings. This is the largest study of such websites conducted in the
United States to date. This update will enable health providers to
better understand the arguments against vaccination and the questions
regarding vaccination that parents and patients may present to them.

Methods

Web pages about vaccination were identified using Copernic Agent
Professional version 6.11 (Copernic Technologies Inc, Saine-Foy,
Quebec, Canada), which is an Internet search program designed to
simultaneously submit searches on numerous engines and return
unduplicated results. The search engines used were AltaVista, FAST
Search (alltheweb.com), Google (which also powers Yahoo! and AOL),
HotBot, Lycos, MSN Web search, Netscape Netcenter, and Teoma. The
search was conducted on December 5, 2003, using the terms “vaccine,”
“vaccination,” “vaccinate,” and “anti-vaccination.” Previous research
showed that sites critical of vaccination were much more likely to be
found with these terms rather than “immunization” [15]. The result was
1138 Web pages representing 750 sites.

The exclusion criteria were as follows: (1) listserv or newsgroup
containing online conversation; (2) information applicable primarily
to animals; (3) posts of brief notices about content on other sites;
(4) online commercial news service, health/medical journal, or
library; (5) non-English language site; 6) exclusively adult
immunization; and (7) inactive links. The inclusion criterion was
content encouraging vaccine refusal or emphasizing the dangers of
vaccines.

Two researchers independently reviewed the sites and agreed that 662
were excluded and 22 were included, but they disagreed on 66 sites. A
third reviewer reviewed these and determined inclusion or exclusion,
leading to a final count of 78 sites.

Data Collection/Website Review
The websites meeting the exclusion and inclusion criteria were
downloaded in 2004 onto a CD using Aeria Leech 3.3 software (Tampa,
FL), which downloads Web content. In this way, all the reviewers
accessed identical information, as content of the websites may change
over time. Criteria for evaluation of the sites were adapted from
published criteria for evaluating health related websites, design and
attribute characteristics used in previous studies in 2000 (eg, links
to other vaccine-critical websites and sale of books, tapes, CDs from
the site), specific vaccine safety concerns (eg, association with
autism, multiple sclerosis), and ethical allegations (eg, conspiracy,
civil liberty violations) [13,16,17]. A list of variables was defined
and, after data collection, was refined. In particular, fifty
variables were defined in detail to minimize interpretation
differences. For each variable, 2 reviewers (1 clinician and 1 social
scientist) independently examined all pages of each website to
determine if the attributes were present (coded as 1) or absent (coded
as 0).

Data Analysis
Interrater reliability for each variable was determined using the
kappa statistic. Variables with a kappa value less than 0.5,
indicating a low level of agreement between the two reviewers, were
not included in further analyses (4 variables). Of the remaining 46
variables, 16 were retained as collected, and 30 were combined into 12
variables using logical groupings (eg, sites promoting alternative
therapies, herbal remedies, or homeopathy as adequate protection
against infectious disease were combined). For combined variables, if
a website was found to have at least one of the individual attributes
present, then the combined variable was coded as being present for
that website. The kappa statistic was calculated for the combined
variables.

To determine the percentage of websites containing each of the
attributes, it was necessary to average the two reviewers' coded
values (ie, if both reviewers coded an attribute as present, the
average was 1; if one reviewer coded the attribute as present and one
reviewer coded it as absent, the average was 0.5; and if both coded
the attribute as absent, the average was 0). These scores were summed
and divided by the total number of websites.

Variable groupings were then created by combining the 28 variables
into the following clusters: promotion of vaccine criticism, emotive
appeals, alternative medicine, disease risk/vaccine safety, and
ethical allegations. Spearman correlations compared total percent
presence of attributes in each cluster to assess whether certain
groups of attributes were frequently found together in vaccine-
critical websites. Analyses were performed using SPSS 12.0 (SPSS Inc,
Chicago, IL).

Results

In total, 78 websites were reviewed. Table 2 lists the website
characteristics, the frequency with which they appeared, and the
interrater reliability for website reviews. The single most common
characteristic of vaccine-critical websites was the inclusion of
statements linking vaccinations with specific adverse reactions,
especially idiopathic chronic diseases such as multiple sclerosis,
autism, and diabetes.

Other common (≥ 75% of websites) characteristics were links to other
vaccine-critical websites, charges that vaccines contain contaminants
that cause adverse events, allegations of conspiracies to hide the
truth about vaccine safety and efficacy, appeals for responsible
parenting through education and resisting the establishment, and
claims that vaccines provide only temporary protection and are
therefore not worth the risk. Examples of the types of vaccine
criticism on the Internet are provided in Table 1.

[view this table] Table 1. Types and examples of vaccine criticism on
the Web

[view this table] Table 2. Types of information on vaccine-critical
websites

Of the 25 website characteristics in Table 2, the average number of
characteristics per website was 13.5 ± 5.3 (range 1.5–23.5). In order
to assess the way in which groups of characteristics were related in
vaccine-critical websites, correlation analyses for nonparametric data
were performed. Although all were significantly correlated (P < .019),
the highest correlation coefficients were for the relationships
between the ethics group and the disease risk/vaccine safety group (ρ
= .637; P < .001), the ethics group and the emotion group (ρ = .542; P
< .001), and the alternative medicine group and the disease risk/
vaccine safety group (ρ = .554; P < .001). Three content design
attributes were identified: 62% of sites contained references to
scientific literature (κ = .60; P < .001); 28% provided links to
vaccine proponents' websites (κ = .68; P < .001); 26% provided
information on or links to states' immunization requirements (κ = .66;
P < .001).

Discussion

We found that websites critical of vaccines claim that vaccines cause
illness, claim that vaccines are contaminated, promote the idea that
the vaccines are only temporarily effective, encourage alternative
medicine, claim conventional medicine is wrong, make emotive appeals,
and make ethical allegations about conspiracy, cover-up, civil liberty
violations, totalitarianism, and immorality.

The Institute of Medicine reviewed the scientific evidence for a
number of vaccine controversies, published multiple texts on the
issues, and has generally found vaccines to be safe, albeit with rare
risks such as anaphylaxis [18-23]. A published review of the veracity
of claims by websites critical of vaccination reports many
“fabrications and distortions” and misrepresentation of the data from
reputable medical journals [24].

The number of vaccine-critical websites may be increasing. We found 78
sites in 2004, whereas Nasir found 51 sites in 1999, and Wolfe et al
found 22 in 2000 [13,14].

Relativism, Logic Fallacies, and Heuristics
We believe that there is a link between the claims we evaluated about
conventional medicine being wrong, about physicians being misinformed
about vaccination, and about the promotion of “back to nature”
alternatives and homeopathy. These are all common in post-modern
thought, which considers truth to be relative and which questions
established points of view. Thus, the viewpoint of a homeopath or
herbalist may be considered as legitimate, or more legitimate, than
the opinion of traditional authorities such as physicians and
scientists. Evidence of this was seen in an analysis of parents of
unvaccinated children in the National Immunization Survey, which found
that 71% said that a doctor is not influential in shaping vaccination
decisions for their children [1].

We found that personal stories or pictures of children allegedly
injured by vaccines appeared on 37% of websites. Information from the
disciplines of logic and debate may help in analyzing and responding
to such allegations. The linking of such alleged adverse reactions
with vaccination appears to commit two logic fallacies. One is post
hoc ergo propter hoc, which translates into “occurring afterwards,
therefore occurring because,” in other words, confusing temporal
association with causality. The second logic fallacy is faulty
dilemma. In this case, the argument forces a choice between two
options, both of which are contrary to a third position, which is not
mentioned as an option. For example, given a description of a disabled
child, the choice is either the vaccine caused the disability or the
child is not disabled; the third option that the disability was
genetically determined or occurred in utero is not mentioned as a
possibility.

Several other heuristic processes may be involved in parental analyses
of vaccine risks, including compression, omission bias, and ambiguity
aversion. Compression is the overestimation of rare risks, such as
vaccine reactions, but an underestimation of common risks, such as the
morbidity and mortality of vaccine-preventable diseases [25]. The news
media tend to overemphasize risk of death from infrequent causes and
to under-represent risk of death from more common causes [26].
Omission bias is the tendency to favor errors of omission over errors
of commission, even though a distinction between them may be
irrelevant [27,28]. Ambiguity aversion applies to cases in which
parents tend to avoid ambiguity and may find a greater risk from a
known disease more acceptable than a smaller, more ambiguous risk from
a new vaccine [25,28]. Ambiguity aversion also applies to a situation
in which there is debate about the reliability of vaccine information.
One study found that those opposed to vaccination were more strongly
opposed after being shown a table comparing the risks of pertussis
disease with the risks of whole cell DTP (diphtheria, tetanus,
pertussis) vaccine, suggesting that they focused on information that
supported their previous beliefs even when presented a balanced
picture [28].

Ethical Allegations
The ethical allegations of conspiracy, cover-up, civil liberty
violations, totalitarianism, and immorality that we found frequently
in websites critical of vaccination are particularly troubling, given
the serious nature of the charges. The handling of the rare cases of
intussusception following vaccination with rhesus monkey-derived
rotavirus vaccine (RRV) challenges the conspiracy and cover-up
allegations. In this case, personnel from the Centers for Disease
Control noted a signal in the vaccine adverse events reporting system
(VAERS), instituted a study, and rapidly found an association between
RRV and intussusception. RRV was withdrawn within weeks [29-31].

Exemptions to states' mandatory vaccination laws are a counter-
argument to the aforementioned ethical allegations. Although state
laws require vaccination prior to school entry, all states allow
exemptions for medical reasons, 48 allow them for religious reasons,
and 17 for philosophical reasons [32]. States that allow philosophical
exemptions to laws mandating vaccination for school entry have
significantly higher rates of unvaccinated children [1].

An analysis of vaccine immorality allegations based on the fact that a
few vaccines are grown in self-propagating cell lines originally
obtained from two abortions in the 1960s was recently published [33].
The paper used strategies to analyze moral complicity (eg, principle
of double effect) and found that vaccination is ethical [33]. The
abortions were past events separated in time, agency, and purpose from
vaccine production. Indeed, the ethics of altruism and herd immunity
argue for widespread vaccination, although concerns about autonomous
decisions and personal conscience should be respected [33].

Historical Context
Since the introduction of smallpox vaccine and compulsory vaccination,
there have been small but vocal movements against vaccinations which
share many similarities with criticisms of the past. First, vaccine
criticism of the past and present capitalizes on the public's lack of
understanding of medical science and investigation and their limited
ability to confirm or refute claims. The general public is not skilled
in interpreting statistical results, in differentiating between
causality and temporal association, or in assessing the validity of
findings based on appropriate study design. Second, many of the
arguments in use today parallel those used in the past. For instance,
during the late 19th century, objections to smallpox and typhoid
vaccinations included the following: vaccination is against the laws
of nature, good hygiene provides adequate protection against disease,
vaccines can transmit other diseases, and compulsory vaccination is a
violation of one's liberty [34,35]. These arguments are similar to
those espoused by current vaccine critics who hold that natural
therapies and alternative medicine are preferable for prevention of
infectious disease, vaccines cause idiopathic illness, and school
entry vaccination requirements violate civil liberties [13,14].
Furthermore, the ethical allegations remain quite strident, including
purported collusion among government, the medical establishment, and
pharmaceutical companies that is motivated by profit [35]. Finally,
opponents of vaccination dramatize relatively rare adverse events to
overshadow vaccination's enormous public health benefits [15]. This is
an especially effective tactic now, as the toll from a number of
infectious diseases fades from the public memory (as a result of
universal vaccinations).

Differences between vaccine criticism of today and the past are
principally a matter of degree. There are now more vaccines and
therefore more available to criticize. Secondly, there are many more
resources for dissemination of health information, including
television, radio, and the World Wide Web.

Strengths and Limitations
This is the largest study conducted by US investigators on this topic
and the most complete and current in the literature. In addition, our
design builds on prior studies by quantifying ethical allegations on
the reviewed websites.

As was the case in prior studies, non-English sites were not reviewed,
which limits the ability to generalize results. Also, interrater
reliability was good but not excellent. We believe that this primarily
reflects inherent individual differences in the interpretation of
website content when determining the presence or absence of value-
related issues such as conspiracy, immorality, and civil liberties
violations. The complexity and size of websites are other factors that
may have affected the interrater reliability.

Solutions
There are several strategies to encourage openness to vaccination
among parents who are concerned about the risk of causing their
children harm from vaccines. These strategies can be used in mass
education campaigns or in discussions between a clinician and parents.
One strategy is to share personal experiences with diseases such as
pertussis, which can cause serious illness and disability and which
still circulates in the United States. Pictures [36,37] and
testimonials [38] of children suffering from vaccine-preventable
diseases may be helpful.

A second strategy is to explain the communicable nature of most
vaccine-preventable diseases and their recurrence in industrialized
countries when vaccination rates decline. For instance, pertussis
returned after immunization rates decreased in Sweden, England, Wales,
and Japan [39-41]. Third, some websites that are critical of
vaccination sell products, including homeopathic and herbal products,
raising the possibility of conflict of interest in these particular
sites—an important point to raise with parents. Finally, non-profit
websites such as the Vaccine Education Center [42] and the National
Network for Immunization Information [43] provide useful information
for parents and providers that is free from commercial and federal
funding.

Conclusions
In summary, websites critical of vaccines allege serious adverse
reactions, vaccine failure, and serious ethical violations, including
cover-up, conspiracy, and civil liberties violations. As physicians
encounter an increasing number of parents and patients who have
searched the Internet for vaccine information, they need to be aware
of the medical and ethical allegations being made against vaccination.
Strategies such as encouraging parents to take the child's
perspective, sharing the physician's experience of treating patients
with vaccine-preventable diseases, and providing pictures and
testimonials of persons affected by vaccine-preventable diseases may
be useful.

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Acknowledgments
This project was supported in part by funding from the Centers for
Disease Control and Prevention (CDC), National Immunization Program,
through U66/CCU719217-03 to the Society of Teachers of Family Medicine
(STFM) Foundation. Its contents are the responsibility of the authors
and do not necessarily reflect the official views of the CDC or STFM.

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TC