As the conflict between the anti-vax movement and public health establishment over the safety of vaccines has escalated, the discussion has devolved from hard science into rhetoric on both sides. Public health officials stridently insist on vaccination as anti-vaxers balk just as vociferously. In the media, public health officials and anti-vax celebrities are often given equal time, out of a misguided desire for “fair balance.” In these debates, the real facts surrounding vaccination get lost in the noise. Just what are the risks of vaccination? Are vaccines safe and effective? Are they truly beneficial to an individual, or only to society at large?
Vaccination is one of the public health triumphs of the 20th century. Yet, in the 21st century, more and more parents refuse to vaccinate their children. Citing risks to their children’s health, such as a supposed link between vaccination and autism, these parents are at the heart of the “anti-vax” movement. Bolstered by such prominent voices as Robert F. Kennedy Jr. and Jenny McCarthy, anti-vaxxer parents stand firm against the advice of their children’s pediatricians, public health outreach programs, and the Centers for Disease Control.
As the conflict between the anti-vax movement and public health establishment over the safety of vaccines has escalated, the discussion has devolved from hard science into rhetoric on both sides. Public health officials stridently insist on vaccination as anti-vaxxers balk just as vociferously. In the media, public health officials and anti-vax celebrities are often given equal time, out of a misguided desire for “fair balance.” In these debates, the real facts surrounding vaccination get lost in the noise. Just what are the risks of vaccination? Are vaccines safe and effective? Are they truly beneficial to an individual child, or only to society at large?
The most frequent claim of anti-vaxxers is that vaccination leads to childhood development of autism. This claim, made prominent by the debunked quack physician Andrew Wakefield (who lost his license to practice medicine for ethical violations including financial conflict of interest), has been thoroughly discredited countless times, and it is well beyond the scope of this post to rehash this tired argument.
How do vaccines cause autism? In short, they, ahem, don’t. The American Academy of Pediatrics has produced a comprehensive document synthesizing all of the evidence surrounding vaccination and autism risk, presenting take-home messages for each study in an easily digestible format. This document, titled “Vaccine Safety: Examine the Evidence,” is available here. The AAP concludes, succinctly, “These studies do not show any link between autism and MMR vaccine, thimerosal, multiple vaccines given at once, fevers or seizures.”
The MMR vaccine, which is protective against infection with the triad of measles, mumps, and rubella, has been made unfairly infamous owing to its centrality in the Wakefield autism scandal. Anti-vax parents routinely shun the MMR vaccine, leading to recent outbreaks across the globe, including a measles outbreak at Disneyland. Clearly, as described above, the MMR vaccine does not cause autism.
For the real risks, we turn to the FDA mandated prescribing information for the MMR vaccine. The prescribing information clearly describes adverse events that may occur as a result of vaccination. Because the vaccine induces an immune response, fever can occur with vaccination. Thus, the vaccine is contraindicated for patients with a history of cerebral conditions for whom fever would be particularly dangerous. Because the vaccine is produced in chick embryo cell culture, the vaccine presents a risk of allergic reaction or anaphylactic shock to patients with a known egg allergy. Similarly, the vaccine contains neomycin, and so patients with a known allergy to neomycin may be at increased risk with vaccination. Few other contraindications have been noted. For the vast majority of children, the MMR vaccine is safe and effective.
Although less manifestly controversial than the MMR vaccine, the influenza vaccine is still routinely avoided by anti-vaxxers. In the United States, vaccination for influenza is accomplished via one of two delivery methods: a nasal spray (FluMist) and an intramuscular injection (Afluria). These vaccines are widely administered and very safe.
As described in the prescribing information for each (available here for FluMist and here for Afluria), adverse reactions are generally restricted to inflammation at the site of administration or fever. Allergies to components of the vaccines provide the primary contraindications, particularly allergy to egg protein. In combination with aspirin therapy, influenza vaccination presents a risk of Guillain-Barré syndrome; therefore, administration of influenza vaccine with aspirin is contraindicated in children and adolescents. For adults and most children, there is little reason not to vaccinate against flu yearly.
One of the claims about vaccines most often repeated by the anti-vax movement is about thimerosal, a mercury-containing preservative that was once commonly used in vaccines. Anti-vaxxers describe thimerosal as a dangerous additive capable of causing autism and interfering with normal brain development in a growing child. No evidence for such claims exists.
However, in part because of the strident claims made about it by anti-vaxers, thimerosal is now used quite rarely; it is found only in one specific type of influenza vaccine. Of note, thimerosal was never contained in the particularly controversial MMR vaccine. Thimerosal was used in several childhood vaccines in the 1990s, but no link was ever found between it and disease. Taken together, the lack of evidence that thimerosal is dangerous coupled with the rarity of its use render it a moot point in the vaccine safety debate.
As concluded by the Centers for Disease Control, “Since 2001, no new vaccine licensed by FDA for use in children has contained thimerosal as a preservative, and all vaccines routinely recommended by CDC for children younger than 6 years of age have been thimerosal-free, or contain only trace amounts of thimerosal, except for multi-dose formulations of influenza vaccine. The most recent and rigorous scientific research does not support the argument that thimerosal-containing vaccines are harmful. However, CDC and FDA continually evaluate new scientific information about the safety of vaccines.”
Based on all available scientific evidence, vaccines are safe and effective, with exceptions in the case of rare conditions such as violent egg allergy. Vaccines do not cause autism. Thimerosal is generally regarded as safe for use in vaccines, has never been associated with an enhanced risk of any disease, and is not contained within the MMR vaccine.
There is no vast conspiracy; vaccination as recommended by public health officials is beneficial to the individual and to society as a whole. For those few patients for whom vaccination is contraindicated, a well-vaccinated population is the only defense against serious disease. Such “herd immunity” is merely a side benefit to vaccination. For each person, except in the case of rare contraindications, the benefits of vaccination far outweigh the risks.