Misconceptions and fear have been fueling the anti-vaccination movement in recent years, particularly with regard to the measles, mumps, and rubella (MMR) vaccine. This is in part because a study published in The Lancet that linked the MMR vaccine to autism (Wakefield et al). In addition to rampant misinformation spread via the Internet, the Wakefield study continues to fuel public concern, despite thorough and unanimous scientific debunking by more than 20 studies (Poland), retraction by all but one of the authors – Wakefield himself — and retraction by The Lancet.
Unfortunately, despite overwhelming scientific evidence that the risks associated with the MMR vaccine are small and uncommon, particularly relative to the serious and more common risks associated with contracting the measles, some parents continue to refuse to immunize their children.
A report by the U.S. Centers for Disease Control and Prevention (CDC) not only underscores the significant risks associated with being unvaccinated for the measles, it also helps demonstrate the fallacious nature of many of the arguments against vaccination and highlights the importance of vaccination in protecting the community.
According to the CDC report, there were more measles cases reported in the U.S. in 2011 than in any of the prior 15 years. A total of 222 cases were reported, the majority of them in people less than 20 years of age. 65% of cases were in unvaccinated individuals, and another 21% of cases were in individuals whose vaccination status was unknown or not on record. Of those who were unvaccinated, a fraction (27 total cases) were under 12 months of age, and were therefore too young for the vaccine.
In light of this disturbing report, some common myths about measles…and the facts:
Myth: Measles is exceedingly rare in the U.S., as vaccination rates are generally high. Unless my children will be traveling to Europe or other parts of the world with higher measles rates, they don’t require measles protection.
Fact: While measles isn’t as common in the U.S. as it is elsewhere in the world (there were no U.S. cases in 2000, for instance), it’s imported from other countries (either by foreign travelers or by U.S. travelers returning from a measles-prone area) and can spread in the U.S., mainly due to unvaccinated individuals. Measles is contagious for about four days before any rash appears, meaning that travelers from foreign countries can bring the disease to the U.S. without being aware that they are doing so. The CDC notes that most cases of measles in the U.S. were brought in from Europe. Further, measles is so contagious that casual exposure to an infected individual (even one who doesn’t yet show signs of the disease) is very nearly 100% effective in transmitting the infection. Measles is spread through the air, meaning that it’s possible to get the disease without any physical contact with an infected individual.
Myth: Measles is a common, routine childhood illness, and there’s no reason to vaccinate for it.
Fact: Measles was common in the U.S. before the introduction of the vaccine in 1963. The disease is so contagious that essentially 100% of the population contracted it prior to the development of the vaccine. Simply because a disease was once common, however, does not mean it is “routine” or harmless. Measles complications are relatively common, and include severe dehydration and pneumonia. 32% of individuals who contracted measles in the U.S. in 2011 had to be hospitalized for complications. Thankfully, there were no deaths among these individuals. However, swelling of the brain and death are possible complications of the disease, occurring in about 3/1000 cases. Even among the individuals who do not require hospitalization, measles is a truly miserable experience. It comes with a high fever, which is accompanied by muscle aches, headache, and sensitivity to light. Unlike chicken pox, to which measles is sometimes erroneously compared because they both cause skin rashes, measles is respiratory and causes a dry cough and extremely sore throat, which contributes to dehydration. The rash can be very extensive (in many cases, it enters the mouth), and itches.
Myth: The MMR vaccine is more dangerous than the measles.
Fact: The MMR vaccine is associated with some mild side effects, including an innocuous and temporary rash in about 5% of vaccinated individuals. Moderate side effects, such as seizure, are very rare, occurring in about 1/3000 doses. Note that the moderate side effects (which are not life-threatening) are three times rarer than the risk of death from the measles. Serious side effects of the MMR vaccine, including death, are so rare that they can’t be statistically quantified. In other words, people die so rarely after getting an MMR that no one can be sure the death was due to the shot.
Myth: Since almost everyone in the U.S. is vaccinated against measles, my child will be protected.
Fact: The vast majority of U.S. citizens are vaccinated against measles. This means that measles won’t be able to take hold and spread across the country in the form of an epidemic, as it could have done before 1963. However, the disease can still spread from one individual to the next, particularly in areas of lower MMR compliance. The 222 cases of measles in the U.S. were primarily due to small outbreaks (there were 17 such outbreaks), where the average outbreak size was 6 individuals. Put another way, for every one case of measles brought into the country by a foreign traveler or returning U.S. citizen, five people who had never left the country got sick.
Myth: If I choose not to vaccinate my children, I’m not hurting anyone but my own family.
Fact: This is not so. To protect a group of people from a disease as effectively as possible, it’s important to keep the vaccination rate as high as possible. The fewer unvaccinated individuals in a population, the less likely that someone with measles will come into contact with an unvaccinated individual, which reduces the likelihood of an outbreak. Vaccines are highly effective — vastly more so than most other medical treatments — but they’re not 100%. This is especially true in children who have had only one of their MMR shots (the CDC recommends a booster at age 4-6). Maximizing the number of immunized individuals helps to protect those for whom vaccination may not be effective. There are also those, including babies under one year of age, who are not eligible for vaccination. Maximizing the vaccination rate among the eligible minimizes the risk to vulnerable members of the population.
If you vaccinate, do you worry about those who don’t? If you don’t vaccinate, what about it makes you uncomfortable?
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 hyperplasia, non-specific colitis, and pervasive developmental disorder in children [retracted in: Lancet. 2010;375(9713):445]. Lancet. 1998;351(1903):637-641.