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In a commentary this month in Mayo Clinic Proceedings, Dr. Gregory Poland discusses the dangers associated with vaccine denialism, defined as the continued propagation of anti-vaccination sentiment and misinformation in the face of overwhelming scientific evidence to the contrary .
Poland points out that the current anti-vaccination movement, which is by no means unique in history, looks particularly unfavorably upon the measles, mumps, and rubella (MMR) vaccine. This is largely due to a since-retracted study published in the Lancet journal by Andrew Wakefield , which suggested a causal link between the MMR vaccine and autism. In his commentary, Poland emphasizes that there are more than 20 well-conducted studies that show no link between MMR and autism, and that scientific societies unilaterally agree that there is no reason to suspect such a link. Nevertheless, fear of autism and other serious adverse reactions to vaccines is having a significant impact upon public health in the United States. Indeed, just this week, inaccurate statements about the HPV vaccine causing mental retardation made the headlines.
As more and more children are withheld from vaccination, the risk of contracting the disease for which they were to be immunized increases. Last year, researchers determined that children whose parents refused the chickenpox vaccine have an 8-fold increased risk of catching the virus compared to fully immunized children.
One of the arguments used by opponents of vaccination is that the diseases for which children are routinely vaccinated aren’t serious, but the adverse reactions associated with vaccines are. U.S. Centers for Disease Control and Prevention (CDC) data, however, demonstrate otherwise. Measles is incredibly communicable — prior to the advent of vaccination, almost 100% of the U.S. population got the disease — and isn’t as innocuous as opponents of vaccination claim. As many as 20% of measles cases in the U.S. result in hospitalization, and six percent of total cases result in pneumonia, which is the major cause of measles-related death. Approximately three of every 1000 individuals infected with measles die.
Reactions to the MMR vaccine, on the other hand, are largely innocuous by comparison. While as many as one in six people vaccinated will experience a fever, these vaccine-related fevers are mild, short-lived, and have no lasting effects. Other mild reactions to the vaccine include a rash (about 5% of those vaccinated) and swelling of lymph nodes. Seizures as a result of the vaccine are considered a more serious consequence, but are very rare, at one in 3000 doses (or one ninth the risk of death from measles infection). Serious reactions include allergy, which happens in less than one in 1,000,000 vaccinations, and debilitating seizures or brain damage, which happen too rarely to quantify and, in fact, are so rare that there’s no way to be sure these events are the result of the vaccination at all. By the numbers, a given individual is many times more likely to die of the measles than to have even a moderate reaction to the vaccine.
The importance of the MMR vaccine, however, doesn’t end with self-interest and personal safety. Vaccines work in two ways: they help to protect the vaccinated individual from infection, and they reduce the likelihood that the disease in question can spread through a population by helping to produce herd immunity.
Because measles is so contagious, 96% of the population must be vaccinated to secure herd immunity, explains Poland. As anti-vaccination sentiment continues to spread, the United States is losing herd immunity, as evidenced by the measles cases reported in the early part of 2011 . In the first six months of this year alone, there have been three times as many measles cases reported as normally seen in an entire year in the U.S. Particularly at risk are babies too young to be vaccinated, as the first dose of MMR isn’t given until an infant is 12 months of age. To leave a vaccine-eligible individual unvaccinated doesn’t just threaten that individual; it threatens the entire community — especially the community’s most vulnerable individuals.
Interestingly enough, anti-vaccine sentiment isn’t new in a historical context. Anti-vaccination movements have gained popularity periodically since the very first laws requiring vaccination, including the Vaccination Act of 1853 that required inoculation of children in the United Kingdom. Public health officials and researchers have noticed that anti-vaccination movements often follow a pattern in which a researcher attempts to explain an otherwise poorly-understood medical phenomenon by tying it to vaccination. While these anti-vaccination studies are generally poorly conducted and irreproducible, they nevertheless ignite fear in the public when they’re reported, and lead to a reduction in vaccination rates. The disease for which vaccination rates have decreased then experiences a resurgence, which results in many avoidable deaths, until such time as the public regains confidence in the vaccine. Examples of epidemics produced as a result of this repeating pattern include the smallpox epidemic in Stockholm in 1873 , the pertussis epidemic in the 1970s in the U.K. , and the Netherlands measles epidemic of 1999 .
Poland suggests that vaccine denialist propaganda does a public disservice, and recommends that it may be time to consider legislating vaccinations for the public good, and to protect vulnerable members of the population. He notes that while anti-vaccination movements call for more research, continued investigation into vaccine safety — particularly with regard to the well-established MMR vaccine — represents a misallocation of limited research dollars, because of the incredible scientific consensus regarding vaccine safety.
- Poland. MMR Vaccine and Autism: Vaccine Nihilism and Postmodern Science. Mayo Clin Proc. 2011 Sep;86(9):869-71.
- Wakefield et al. Ileal-lymphoid-nodular hy- perplasia, non-specific colitis, and pervasive developmental disorder in children [retracted in: Lancet. 2010;375(9713):445]. Lancet. 1998;351(1903):637-641.
- Centers for Disease Control and Prevention (CDC). Measles: United States, January–May 20, 2011. MMWR Morb Mortal Wkly Rep. 2011 May 27;60(20):666-8.
- Nelson et al. The right to die? Anti-vaccination activity and the 1874 smallpox epidemic in Stockholm. Soc Hist Med. 1992 Dec;5(3):369-88.
- Gangarosa et al. Impact of anti-vaccine movements on pertussis control: the untold story. Lancet. 1998 Jan 31;351(9099):356-61.
- Centers for Disease Control and Prevention. Measles outbreak–Netherlands, April 1999-January 2000. MMWR Morb Mortal Wkly Rep. 2000 Apr 14;49(14):299-303.