Date Published: June 12, 2018
Publisher: Public Library of Science
Author(s): Jacqueline K. Olive, Peter J. Hotez, Ashish Damania, Melissa S. Nolan
Abstract: In a Policy Forum, Peter Hotez and colleagues discuss vaccination exemptions in US states and possible consequences for infectious disease outbreaks.
Partial Text: NME data were collected from all 18 states currently permitting philosophical-belief NMEs (Arkansas [AR], Arizona [AZ], Colorado [CO], Idaho [ID], Louisiana [LA], Maine [ME], Michigan [MI], Minnesota [MN], Missouri [MO], North Dakota [ND], Ohio [OH], Oklahoma [OK], Oregon [OR], Pennsylvania [PA], Texas [TX], Utah [UT], Washington [WA], and Wisconsin [WI]). Of note, MO permits philosophical-belief exemptions only for child care facilities, but not public schools. Sixteen of the 18 states also allow religious exemptions, except LA and MN: “The existing statute in Minnesota and Louisiana does not explicitly recognize religion as a reason for claiming an exemption; however, as a practical matter, the non-medical exemption may encompass religious beliefs” . VT, CA, MS, and WV were excluded from our analysis because they no longer have NMEs in their respective states. From our 18 included states, state-level data were collected from state health departments and/or the US Centers for Disease Control and Prevention (CDC)  and analyzed by school year from 2009–2010 to 2016–2017. The state NME rate is represented by the number of entering kindergarteners with a documented NME out of the total kindergarten enrollments in the state. Specifically, the data were obtained from CDC Morbidity and Mortality Weekly Report’s (MMWR) annual reports (AR, AZ, CO, ID, LA, ME, MI, MN, MO, ND, OH, OK, OR, PA, TX, UT, WA, and WI) and state health departments (AR, AZ, ID, LA, MI, MO, ND, OR, PA, and UT). CDC data from the 2010 to 2011 school year was not available for analysis; however, 10 of the 18 states individually provided data for the 2010 to 2011 school year. Because all data are represented as aggregated totals and not personally identifying, an exemption was obtained from the Baylor College of Medicine Institutional Review Board for this study.
Beyond the statewide data, many county-level NME rates were publicly available from state health departments for the school year 2016 to 2017. State- and county-level data included in our analysis have also been made publicly accessible (doi 10.6084/m9.figshare.6288968). County NME rate is defined as the number of enrolling kindergarteners with an NME out of the total kindergarten enrollments (public and private) in the county. Some data inconsistencies were present, including some missing county data for 3 states (AR, ND, OR), absent county data for 4 states (CO, LA, OH, and OK), and lacking data from the year 2016 to 2017 for 3 states (AR, PA, and TX). For AR, PA, and TX, we used data from the 2015 to 2016 school year. Missing data from NME-permitting states were either not collected by the state or publicly inaccessible.
Whereas measles was thought to have been eliminated from the US in 2000, we have seen local outbreaks of this vaccine-preventable disease and others, like measles and pertussis (whooping cough), in recent years due to inadequate immunization coverage in schools. For instance, a child with an NME from the measles, mumps, and rubella (MMR) vaccine is 35 times more likely to contract measles than is a vaccinated child . Moreover, a child without the diphtheria, tetanus, and acellular pertussis (DTaP) vaccine is 3 times more likely to contract pertussis than is a vaccinated child . NMEs weaken herd immunity that protects the population at large, particularly children who are unable to get vaccinated for medical reasons. The target vaccination coverage rate to achieve the ideal herd immunity is 90% to 95%, depending on the infectious agent . To evaluate the influence of NMEs on vaccine uptake, Spearman correlation was calculated between state NME rate (%) and MMR vaccination rate (%) for 20 states either allowing NMEs (OK was excluded due to lack of MMR vaccine data) or 3 control states prohibiting NMEs in the 2016 to 2017 school year (CA, MS, WV) (CDC MMWR annual report) using R programming language (version 3.4.2) with the “cor.test” function. As shown in Fig 4 and Table 3, there was a significant inverse association between state NME rate and MMR vaccination rate by Spearman correlation (P = 0.03; Fig 4) and beta regression (P = 0.007). Similarly, we calculated Spearman correlation between state NME rate and MMR rate for all 50 US states and the District of Columbia. States with no information for either NME rate or MMR vaccination rate were excluded (CO, IL, MN, MO, OK, and WY). From this analysis, we found a significant inverse association between state NME rate and MMR vaccination rate (P = 0.04) as compared to states allowing NMEs. Overall, states with more NME students exhibited lower MMR vaccination rates. In contrast, states that have banned NMEs—MS, CA, and WV—exhibit the highest MMR vaccine uptake and lowest incidence of vaccine-preventable diseases.
Our analysis reveals that, since 2009, NMEs have risen in 12 of the 18 states that currently allow philosophical-belief exemptions. A recent analysis found that the average annual change in state vaccine exemption rates in recent school years has begun to level off nationally, whereas it had been increasing in earlier years . In at least one-half of the 18 states allowing NMEs, the rates have begun to plateau over the last few years. However, it is important to note that NMEs continue to rise in at least one-third of the 18 states, with no signs of slowing in those rates. In addition, in those states with plateauing levels, the potential for outbreaks still exists.