Antivaccination movements often can have a significant effect on public health, primarily as a result of outbreaks of vaccine-preventable diseases. But, are the fears and concerns of the antivaccination movement unwarranted? What is the trade-off between benefit and risk? While 19th- and early-20th-century fears of vaccination might have been based on anecdotal horror stories, vaccine safety is a real and constant concern. New vaccines and vaccine combinations that provide a wider array of protection from diseases often require more injections, which, in rare cases, may lead to serious reactions. As with other pharmaceutical products, vaccines can produce side effects ranging from local injection-site soreness or redness to low-grade fevers to more serious adverse events. Therefore, safety concerns are not entirely off base. Public health experts believe that the system of routine childhood immunizations rests on a tenuous foundation of public support. Primarily because the success of immunization programs depends on parents’ beliefs that vaccinating their children is safer than not doing so, it is imperative that parents and the public understand the risks as well as the benefits of vaccination. Parents should understand the consequences of choosing not to vaccinate. For some diseases, for example, pertussis, unvaccinated children are much more likely to contract the disease compared with children who are vaccinated.

Yet, all it takes is the hint of vaccine-safety controversy to scare off people from getting vaccinated. For example, in 1976, there was a scare that the swine influenza vaccine was associated with a severe paralytic illness called Guillain-Barre Syndrome (GBS). During the 1976-1977 swine influenza vaccination campaign, for example, 1,300 cases of GBS were reported to the CDC.[54] According to the CDC’s vaccine information sheet on the influenza vaccine, if there is a risk of GBS from this influenza vaccine, it is estimated at one or two cases per million persons vaccinated, much less than the risk of severe influenza. Nevertheless, at that time, fear of developing GBS after a flu shot heightened distrust of getting an influenza vaccination. The overwhelming majority of people who get the influenza vaccine have no serious problem from it.

Also in the 1970s, when a suggested connection between the DPT vaccine and neurological damage in children was alleged, acceptance of this vaccine plummeted, resulting in a widespread resurgence of pertussis, especially in Great Britain where parents refused to have their children immunized.[55] Many parents who chose not to vaccinate their children doubted the reliability of vaccination information from authorities, believing that doctors overestimate protection and underestimate dangers of vaccines.[56] Furthermore, vaccines have been so effective that many parents, thankfully, have never seen cases of diseases against which vaccines protect, which in a sense diminishes the vaccine’s perceived value and creates apathy.[57] A survey showed that 25 percent of those polled felt that children receive more vaccines than needed.[58] Between 1990 and 2000, for example, vaccines against four diseases (Haemophilus influenza type B, hepatitis B, chicken pox, and pneumococcal disease), entailing 10 to 12 injections, were added to the immunization schedule. Parents felt that children were becoming “pediatric pin cushions.”[59]

The antivaccination movement, both in the United States and abroad, has been facilitated by the Internet, a fertile breeding ground for dissemination of information both correct and incorrect. Several studies have evaluated the information posted on the Internet, and the results are troubling. One study found that almost 43 percent of online sites about the MMR vaccine were negative and contained inaccurate and unbalanced information.[60] The most frequently cited incorrect information was that vaccines cause other illnesses such as neurologic disorder, multiple sclerosis, autism, asthma, and sudden infant death syndrome. Other common bits of information were that vaccines contain potentially large amounts of contaminants and mercury.[61]

The media, perhaps unintentionally, also fuels antivaccination sentiments. The power of the media to influence vaccination policy is illustrated by the impact of a British television documentary that aired in 1974 showing children allegedly harmed by vaccines. In the United States, too, a 1982 television special on the DPT vaccine included interviews with families alleging that their children were brain damaged after being vaccinated. By insinuating a cover-up, the media played into the fears of the antivaccination movement. Though heavily criticized by physicians and scientists, the show won an Emmy.

More recently, in 1998, British scientists, led by Andrew Wakefield, published an article in Lancet suggesting a connection between the MMR vaccine and autism.[62] Before the study (which was based on only 12 cases) could be adequately evaluated by the scientific community, the lay press in both the United Kingdom and the United States picked up on the article. The authors of the article eventually retracted the assertion of a link between the MMR vaccine and autism, but the public’s confidence in the MMR vaccine was certainly shaken. Immunization rates for MMR fell despite the fact that British and American governments advised parents not to reject MMR vaccinations. Wakefield’s “research” was shoddy at best. His license to practice medicine was revoked as a result of the scandal.

Another controversy that engaged the antivaccination movement was the use of thimerosal, a mercury-containing organic compound, as a preservative to extend the shelf life of some vaccines. It was suggested that thimerosal in childhood vaccines could contribute to, or cause, a range of neurodevelopmental disorders in children, including attention-deficit/hyperactivity disorder. The critics argued that the ethylmercury-based preservative could cause serious side effects when administered to young children who have relatively undeveloped immune and neurological systems.

These concerns provided the impetus for the passage of the FDA Modernization Act of 1997, which called for a review and risk assessment of mercury-containing food and drugs. The FDA’s Center for Biologics Evaluation and Research investigated the issue and found that some children could have exceeded the federal guidelines for single-dose mercury exposure, but the results were inconclusive. A 2004 IOM report on the subject concluded that the evidence did not support a causal relationship between thimerosal-containing vaccines and autism, although a congressional investigation did find evidence that thimerosal posed a risk.[63] The actual amount of thimerosal present in vaccines for children is listed, usually labeled as “trace” or nil. Currently, adolescent and adult tetanus vaccine and certain influenza vaccines still contain thimerosal.

###

Tony Rosen, MPH, MD
Tony Rosen, Division of Geriatric Medicine and Gerontology, Weill Cornell Medical College, Cornell University, New York, New York;

###

REFERENCES

1. Barquest N, Domingo P. Smallpox: the triumph over the most terrible of the ministers of death. Ann Internal Med. 1997;127:627.
2. US Centers for Disease Control and Prevention. Ten great public health achievements in the twentieth century, 1900-1999.
3.   Parker AA. Implications of a 2005 measles outbreak in Indiana for sustained elimination of measles in the United States. New Engl J Med. 2006;355:1184.
4. Okonek BAM, Peters PM. Vaccines: how and why
5. Baxby D. Vaccination: Jenner’s Legacy. Berkeley, UK: Jenner Educational Trust; 1994. 6. Parish HJ. A History of Immunization. Edinburgh, UK: Livingstone; 1965.
6. Gross CP, Sepkowitz K. The myth of the medical breakthrough: smallpox, vaccination, and Jenner reconsidered. Int J Infect Dis. 1998;3:54-60.
7. Salmon DA,  et al.  Compulsory vaccination and conscientious or philosophical exemptions: past, present, and future. Lancet. 2006;367(9508):436-442.

Full References  »