Vaccine Nonmedical Exemptions May Jeopardize Population Health, Study Finds

A new research study from the Baylor College of Medicine finds that vaccine nonmedical exemption (NME) rates are inversely associated with vaccine coverage—especially for measles, mumps, and rubella (MMR)—in certain geographic locations, which can increase the likelihood of preventable outbreaks in those regions.

According to the CDC, infant vaccination rates in the United States hovered around 72% in 2015 for 7 vaccines, including diphtheria, tetanus, pertussis, MMR, H. influenzae type b, hepatitis B, chicken pox, and pneumococcal conjugate vaccine. However, growing parental concerns with the safety of vaccines has resulted in parents seeking NME (based on their religious or philosophical beliefs) for their preschooler or kindergartener. In addition to medical exemptions—for children in whom medical reasons contraindicate vaccines—18 US states have an NME provision.

In their present study, published in PLoS Medicine,¹ the authors collected data from all 18 states that allow philosophical-based NMEs, of which only 16 allow religion-based NMEs. The authors sourced their state-level data from either CDC or the respective state health departments, starting in school year 2009—2010 up to 2016–2017.

Overall, the authors noted a significant (P <.05) upward trend in kindergarteners enrolling with NMEs since the year 2009 in 12 of the 18 states: Arizona, Arkansas, Idaho, Maine, Minnesota, Missouri, North Dakota, Ohio, Oklahoma, Oregon, Texas, and Utah. An accelerated rate of NMEs was specifically noted between 2009 and 2014, which plateaued for some states between 2014 and 2017. However, the authors note a steady rise in NMEs for Arkansas, North Dakota, Ohio, Oklahoma, Texas, and Utah to date.

A further granular view of county-level data identified several metropolitan areas as having high numbers of NMEs. The authors sorted them out geographically as:

• Northwest: Seattle (WA), Spokane (WA), and Portland (OR)
• Southwest: Phoenix (AZ), Salt Lake City (UT), Provo (UT), Houston (TX), Fort Worth (TX), Plano (TX), and Austin (TX)
• Midwest: Troy (MI), Warren (MI), Detroit (MI), and Kansas City (MO)
• Northwest: Pittsburgh (PA)

Pointing out the herd-immunity effect associated with vaccination, the authors write that these densely populated urban regions can be potential epicenters for “outbreaks of vaccine-preventable diseases.” Although measles was thought to have been eradicated in the United States, there have been reports of local outbreaks of the disease, along with pertussis, due to inadequate immunization coverage in schools. The target vaccination rate to achieve herd immunity is 90% to 95%, depending on the virus.

A child who has not received the diphtheria, tetanus, and acellular pertussis vaccine is 3 times more vulnerable to contract the pertussis virus² and a child who didn’t receive the MMR vaccine is 35 times more vulnerable to contract measles,³ both compared with a vaccinated child. Tapping further into the association of NMEs with vaccine uptake in 20 states—which excluded Oklahoma and included California, Mississippi, and West Virginia as the control states prohibiting NME&mdash;the researchers observed a significant inverse Spearman correlation (P = .03). States with more NME students exhibited lower MMR vaccination rates (P = .007), the authors write, while the 3 states that banned NMEs had the highest MMR vaccine uptake and lowest incidence of vaccine-preventable diseases.

New foci of antivaccine activities are being established in major metropolitan areas, rendering select cities vulnerable for vaccination-preventable diseases, the authors conclude from their findings.

References

1. Olive JK, Hotez PJ, Damania A, Nolan MS. The state of the antivaccine movement in the United States: A focused examination of nonmedical exemptions in states and counties. PLoS Med. 2018;15(6):e1002578. doi: 10.1371/journal.pmed.1002578.
2. Robison SG, Liko J. The timing of pertussis cases in unvaccinated children in an outbreak year: Oregon 2012. J Pediatr. 2017;183:159-163. doi: 10.1016/j.jpeds.2016.12.047.
3. Salmon DA, Haber M, Gangarosa EJ, Phillips L, Smith NJ, Chen RT. Health consequences of religious and philosophical exemptions from immunization laws: individual and societal risk of measles. JAMA. 1999;282(1):47-53. doi: 10.1001/jama.282.1.47.