It Takes a Herd to Make A Difference

Vaccines are considered to be one of the greatest achievements in the history of public health. Smallpox was officially declared to be an eradicated disease in 1980 (the last recorded case was in Somalia in 1979) (1). Cases of poliomyelitis (polio) have dropped to only 22 reported cases in 2017 from nearly 350,000 cases in 1988 (2). These landmark achievements can be attributed to the success of modern vaccines.  Despite these huge successes, anti-vaccination movements have been around since Edward Jenner created the first smallpox vaccine in the early 1800s. Although times have changed, anti-vaccination movements have remained relatively consistent (3). Vaccine critics have expressed a wide variety of concerns, most of which are with regards to safety and efficacy (3,4).

“If vaccines are so effective, why are there so many people that refuse vaccines?”

The modern anti-vaccination movement can be traced back to the research of Andrew Wakefield in 1998. Wakefield claimed to have discovered a link between the measles, mumps, and rubella (MMR) vaccine and autism (5). Following it’s publishing in The Lancet, the media (and political figures) began citing this paper and ignited a public fear of vaccines. Years later, the General Medical Council in the UK found that Wakefield falsified the data in his report and had a huge financial conflict of interest. His research was funded by a law firm that was representing parents who believed vaccines harmed their children. In February of 2010, Wakefield lost his medical license and The Lancet retracted his paper. A large number of extensive research studies have since assessed the safety of the MMR vaccine. None of these studies have found a link between the MMR vaccine and autism (6).

Although his paper was falsified and retracted, Andrew Wakefield’s study continues to be cited today and is still used to fuel anti-vaccination movements.

“But MY decision to refuse vaccines won’t affect anyone else.”

This couldn’t be further from the truth. In reality, the decision to refuse vaccines for yourself (or your children) actually affects a huge proportion of the population. Some people, like those with allergies or those that are immunocompromised, literally cannot receive vaccines. This is where something called “herd immunity” kicks in. Infectious diseases can travel quickly from person to person. If enough people in a community are vaccinated, the disease will be less likely to spread and the entire community is less likely to get sick. For every infectious disease out in the world, there needs to be a certain percentage of people that are vaccinated against the disease in order to protect unvaccinated people from infection. In the case of measles, ~90-95% of the entire population needs to be vaccinated in order to achieve herd immunity. The remaining 5% of the population that doesn’t need to be vaccinated should really be reserved for those who can’t receive vaccines for legitimate health reasons (7).

“Even if I don’t get vaccinated, herd immunity will surely protect me.”

Let’s go back to the measles example: 90-95% of the entire population needs to be vaccinated to achieve herd immunity. The assumption for this is that vaccinated people are distributed equally amongst the population; this actually isn’t the case. The proportion of vaccinated to unvaccinated people is highly variable on a state, county, and even school level. So while 90-95% of the United States population might be vaccinated, your local population could be even lower (6). In late 2014, dozens of unvaccinated children were exposed to and, consequently, infected with the measles virus at Disneyland, California. This is a pretty big deal considering measles was declared eliminated from the United Stated in 2000 (8). It’s important to note that measles is endemic in certain areas of the world. Just because a certain disease has “disappeared” from the United States doesn’t mean that you don’t need to be vaccinated. International travel brings diseases to the United States all the time. Anyone who is healthy enough to get vaccinated should definitely do so.

With increased awareness, we can all help to reduce the prevalence of vaccine-preventable diseases across the globe. Staying up-to-date with booster shots and getting your annual (and usually free!) flu shot are great ways to stay happy and healthy while protecting your peers as well!

 

 

 

To learn more about vaccines and vaccine-preventable diseases, go to https://vaccines.gov .

To donate to the global polio eradication initiative, go to https://www.endpolio.org/donate . All donations are matched 2:1 by the Bill and Melinda Gates Foundation!

  1. “Smallpox.” World Health Organization, World Health Organization, www.who.int/csr/disease/smallpox/en/.
  2. “Poliomyelitis.” World Health Organization, World Health Organization, www.who.int/mediacentre/factsheets/fs114/en/.
  3. “History of Anti-Vaccination Movements.” History of Vaccines, www.historyofvaccines.org/content/articles/history-anti-vaccination-movements.
  4. McKee, Chephra, and Kristin Bohannon. “Exploring the Reasons Behind Parental Refusal of Vaccines.” The Journal of Pediatric Pharmacology and Therapeutics : JPPT 21.2 (2016): 104–109. PMC. Web. 11 Apr. 2018.
  5.  Wakefield AJ et al. Ileal-lymphoid-nodular hyperplasia, non-specific colitis, and pervasive developmental disorder in children. Lancet. 1998;351:637–41.
  6. “Vaccine Myths Debunked.” PublicHealth.org, 12 Dec. 2017, www.publichealth.org/public-awareness/understanding-vaccines/vaccine-myths-debunked/.
  7. U.S. Department of Health and Human Services. “Vaccines Protect Your Community.”Vaccines.gov, U.S. Department of Health and Human Services, 11 Oct. 2006, www.vaccines.gov/basics/work/protection/index.html.
  8. “Emergency Preparedness and Response.” Centers for Disease Control and Prevention, Centers for Disease Control and Prevention, emergency.cdc.gov/han/han00376.asp