Faculty Editor: Professor Heather Olins

Since they first made an appearance in medicine, vaccines have been some of the most effective tools for disease prevention worldwide.  However, in order for vaccines to be effective for an entire region, there must be a significant proportion of vaccinated individuals in the population.  In recent years, there has been a measurable increase in vaccine refusal in the United States, and the largest group of refusals is in children who are exempt from school immunizations for a nonmedical reason.1  We can also see evidence that geographic clustering of vaccine refusal correlates with disease outbreaks.2  Those who go unvaccinated put not only themselves in danger, but all of those around them, including such exceptionally vulnerable groups as infants too young to receive a vaccination, those whose health makes immunization an inviable option, and those whose immune system has not responded effectively to a vaccination.3

The association between a higher rate of vaccines and a decrease in disease prevalence over time is irrefutable.  When a large proportion of individuals are vaccinated, it results in a high resistance in the population overall. This is known as herd immunity, and basically eradicates the disease from the population.  In order to better ensure this immunity, vaccine requirements are often enacted by local or federal governments. The first such requirement in the United States was passed in Massachusetts in 1809 to control outbreaks of smallpox.4  Other states followed suit, and this procedure was accepted and successful until unorthodox medical professionals began advocating opposing theories.  Levels of vaccination decreased, and naturally, smallpox returned and vaccination rates rose again.5  This cycle of vaccine perception is one that can be seen time and again ever since.  In 1905, the Supreme Court case Jacobson v. Massachusetts endorsed state rights to pass and enforce compulsory vaccination laws.6  Record lows in the rate of vaccine-preventable diseases have been attributed to such policies as immunization requirements for school entry, which all states had by the beginning of the 1980’s.7  Unfortunately, an increase in enforcement of vaccine regulations is almost always followed by greater vaccine opposition.

The downside of living in a world in which vaccines have been around since before our time is that immunity to certain illnesses is often taken for granted.  Having never seen a high incidence rate of diseases that are now preventable by vaccines, the public is less aware of the severity of these diseases.8  Parents become less concerned about the effects that an illness like measles could have on their children, because it seems so improbable.  Instead, they redirect this worry towards the very real vaccines to which their children are subjected. One example of this comes from a later-discussed San Diego measles outbreak in 2008, during which 41 percent of parents who had previously declined the measles vaccination for their child accepted it once they saw other children becoming infected.9

Most states allow parents to opt their children out of mandatory vaccinations for various reasons; either philosophical, religious, or medical. Philosophical reasons include non-natural elements of the vaccine, and the most common religious objection is the use of fetal tissue in vaccine production.10  As of March 2008, all 50 states permitted medical exemptions, 48 states allowed religious exemptions, and 21 states allowed philosophical.11  Over the past few decades, the rate of such non-medical exemptions has increased across the United States, even in states whose mandatory vaccine exemption process is fairly complex and difficult to traverse.12  

  Certain vaccines, such as those protecting against the human papilloma virus, can also cause a moral dilemma with parents.  Parents who may approve of vaccinating their children against such illnesses as the mumps and measles could see this as an overreach.  Mother Deepi Brar from Oakland, California expressed her concerns, stating, “Since it’s not a communicable disease you can catch in a classroom setting, it’s not really the school’s place to tell parents that they must go out and have their children vaccinated.”13  Since the vaccine helps to prevent a sexually transmitted disease, religious groups often get involved as well, such as the Texas Eagle Forum, which flooded the governor’s office with calls protesting the mandate requiring this vaccine for high school females.14   Some were even concerned about gender discrimination since the burden to protect reproductive health would fall upon the female teenagers alone.15  Many parents prefer to put this vaccination off because of its association with STDs, which they are uncomfortable exposing their children to the idea of.  However, the vaccine has been proven more successful when given to someone who is not yet sexually active. HPV is the most commonly transmitted STD in the United States, and 2 of the 4 strains protected against by the vaccination are responsible for 70% of cervical cancer cases, which kill around 1/3 of infected females yearly.16  The personal belief behind vaccine opposition that seems to be the most reported on today, however, is the link between vaccination against measles, mumps, and rubella and the onset or diagnosis of autism in children.

Due to these qualms, several studies have been conducted to collect more information on the validity of suspected downsides of vaccines.  One such study took place in Denmark from January 1, 1991, to December 31, 1998 which tested the association between the MMR vaccine and autistic-spectrum disorders.  The vaccine from the study was the same one being used in the United States.17  Once the vaccinated children reached one year of age, they began follow-ups for autistic-spectrum disorders, which continued until there was a diagnosis, the individual moved or died, or the study ended.18  It is extremely likely that any severe cases of autism would be diagnosed and reported due to the comprehensive nature of health care surveillance for children in Denmark at this time.19  The study found the probability of a link between autistic-spectrum disorders and vaccinated children to be very low, and that for autistic disorder was even lower.20  No association with other variables like age when vaccinated were found.21  This study is able to conclusively provide strong evidence against any causality between or association of the MMR vaccine and autism.

A similar study was run by The National Board of Health and National Public Health Institute in Europe in 1982.  Around 3 million MMR vaccines were administered, and not one vaccinated individual was diagnosed with autism.22

A nationwide retrospective study in the United States from 1985 to 1992 showed that children with vaccine exemptions were 35 times as likely to contract measles than those who were vaccinated.23  In Colorado, the county incidence of measles and pertussis, more commonly known as whooping cough, in vaccinated children from 1987 to 1998 was associated with the frequency of exemptions in that county, and at least 11 percent of children who acquired measles during this time were infected through contact with an exempt child.24   After nearly being eradicated, there were 64 cases and 5 outbreaks of measles from January 1st to April 25th of 2008.25  63 of the 64 infected individuals were unvaccinated or did not have vaccination records, and 67 percent of infected children had a non-medical exemption.26  Similar figures are seen time and again in comparable outbreaks and studies.

In the early 90’s the measles outbreaks that occurred in multiple countries were attributed to the suboptimal vaccine coverage in preschool aged children.27  In 2008, an unvaccinated 7 year old boy was infected with measles in Switzerland, and upon return to the United States, sparked the largest San Diego outbreak since 1991.28  75% of the resulting cases were in individuals who were intentionally unvaccinated.29  In 2014, a measles outbreak originated in Disneyland in Anaheim, California.  Around half of the 111 cases were among those who were eligible but intentionally unvaccinated.30  Since January 1st, 2000, 56.8% of reported measles cases involved individuals who had no history of a measles vaccination, and unvaccinated patients represented a larger proportion of total cases in earlier weeks of an outbreak.31  On top of that, in the five largest recent statewide pertussis outbreaks, 28-45% were vaccinated less than reccommended, with risk being proportional to the number of the 3 vaccinations given.32  At least 6 observational studies are able to show a correlation between an increased risk of pertussis in that community or state and vaccine exemption rates, and states with simpler vaccine exemption rates are up to 1.5 times more likely to have an elevated rate of pertussis.33  There are countless other examples with similar results.

Clustering of vaccine refusals can be caused by cultural issues, socioeconomic status, level of educational, the beliefs of local health care providers, or local media coverage.34  Parents may also be hesitant due to their own waning confidence in medical professionals, corporations, and even the healthcare system as a whole.35  Studies have shown that in recent years, unvaccinated children are more often white, male, and from families who believe their children have a low susceptibility to the diseases in question.  These families are more likely to have a with a high income, married mother with a college education, and four or more children.36  This is a shift from the 1980’s and 1990’s, when under- and unvaccinated children were most likely to live in impoverished inner-cities, be ethnic or racial minorities, and have mothers with low levels of education, all contributing to diminished access to proper health care.38  69% of parents who choose to exempt their children from vaccinations do so because of concerns regarding the harmful effects of said vaccines, and the majority of parents have similar opinions of vaccines to that of their child’s primary care physician.37  

It is known that young children are more susceptible to illness and death from infectious diseases, and data show that vaccine rates decline unless the vaccination is mandated.39  In order to decrease the rate of vaccine exemptions, research should be done on the production of vaccines with different ingredients that may be more appealing to all lifestyles.  Parents have revealed that the source they most frequently receive immunization information from is a health care provider.40  Thankfully for children who would suffer from exposure to unvaccinated children, 40% of pediatricians said they would refuse care to a family that refused all vaccines, and 28% said they would refuse care to a family that refused some vaccines.41  However, there is obviously room for improvement in these numbers.  As individuals in charge of the health and well-being of each and every member of society, it is important that healthcare professionals as a whole accept the facts that well-designed studies have proven, and teach parents the importance of vaccinations for the sake of their both children and their community.  Recently in the United Kingdom, measles became an endemic disease again after reaching eradicated-status.42  Hopefully we are able to enact some of these measures before the same happens in the United States.


  1. https://www.nejm.org/doi/full/10.1056/nejmoa021134 [17] [18] [19] [20] [21]
  2. https://www.thelancet.com/journals/lancet/article/PIIS0140-6736(98)24018-9/fulltext?code=lancet-site [22]
  3. https://www.thelancet.com/journals/lancet/article/PIIS0140-6736(07)60475-9/fulltext?code=lancet-site&dgcid=recommender_referral_trendmd [13] [14] [15] [16] [39]
  4. https://www.nejm.org/doi/full/10.1056/nejmsa0806477 [1] [2] [3] [4] [5] [6] [7] [8] [11] [23] [24] [25] [26] [34] [36] [37] [39] [41]
  5. https://jamanetwork.com/journals/jama/fullarticle/2503179?tab=cme [10] [12] [27] [30] [31] [32] [33] [35] [40]
  6. http://pediatrics.aappublications.org/content/early/2010/03/22/peds.2009-1653.short [9] [28] [29] [38] [42]

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