Nonmedical Exemptions From School Immunization Requirements: A Systematic Review

We summarized studies describing the prevalence of, trends in, and correlates of nonmedical exemptions from school vaccination mandates and the association of these policies with the incidence of vaccine-preventable disease.We searched 4 electronic databases for empirical studies published from 1997 to 2013 to capture exemption dynamics and qualitatively abstracted and synthesized the results. Findings from 42 studies suggest that exemption rates are increasing and occur in clusters; most exemptors questioned vaccine safety, although some exempted out of convenience. Easier state-level exemption procedures increase exemption rates and both individual and community disease risk.State laws influence exemption rates, but policy implementation, exemptors’ vaccination status, and underlying mechanisms of geographical clustering need to be examined further to tailor specific interventions.Childhood vaccinations are one of the most significant public health interventions of all time. They reduce the risk of contracting dangerous vaccine-preventable childhood diseases on the individual level and, when immunization coverage is high enough, confer herd immunity at the population level for those diseases that are contagious.1,2 Recognizing the public health importance of the childhood immunization schedule, all 50 US states require parents to provide documentation of immunization for admission to school and day care, a mandate that has been crucial for achieving widespread vaccination.1,2 However, all states also allow medical exemptions for those children unable to receive vaccines for medically contraindicated reasons.3 Exemption laws in all but 2 states (Mississippi and West Virginia) also provide for nonmedical exemptions (NMEs) on the basis of parents’ religious, philosophical, or personal beliefs. NMEs are considered an important mechanism to balance child welfare and the protection of public health with parental rights.4,5 Although some have argued that NMEs should not be allowed because parents who choose not to immunize their children put their own children and others at risk,6 others believe that the negative consequences of exemption are not sufficient to justify violating parental autonomy.As concerns about vaccine safety have increased over the past 15 years, more parents are choosing to refuse or delay vaccines.3,7 This increase in vaccine hesitancy can be seen at the point of school entry in the rising rates of NMEs. Furthermore, NMEs from school-entry immunization mandates are receiving increased policy and public health scrutiny because exemption rates within and across schools have significant epidemiological implications. Where NME rates are high enough to compromise herd immunity at the local level, the risk of vaccine-preventable disease outbreak increases. Understanding the spatial and social patterning of NMEs is therefore critical to infectious disease prevention and control efforts.Over the past decade, rising attention to vaccine hesitancy and NMEs has prompted several state legislatures to introduce, consider, and in some cases enact new exemption laws. In 2003, Arkansas, which previously only allowed medical and religious exemptions, started allowing philosophical exemptions on the condition that parents provided a notarized statement requesting an exemption, completed a vaccination education component, and signed a statement acknowledging the receipt of vaccination information.8,9 Similarly, in 2003, Texas also started to allow philosophical exemptions, requiring those who wanted to exempt to obtain a form from the Texas Department of Health and declare their objections in an affidavit.10 Conversely, Washington, Oregon, and California, all of which previously had lenient exemption policies and, particularly in the case of Washington and Oregon, very high exemption rates, recently made the process for claiming an exemption harder by requiring a signed statement from a health care practitioner that the parent had been informed of the risks and benefits of immunization. In the 2011–2012 legislative cycle, bills to tighten or eliminate NMEs were introduced in 3 states, whereas bills to expand or allow NMEs were proposed in another 10.11Continued increases in vaccine refusal and NME rates and the growing attention to NMEs in state legislatures underscore the importance of understanding the determinants of NMEs, the impact of state NME policies, and the epidemiological implications of NMEs for vaccine coverage, herd immunity, and disease outbreak risk. The goal of this systematic review, therefore, is to summarize the recent evidence on NMEs, including the prevalence of, trends in, and correlates of NMEs and the association of these exemptions and exemption policies with the incidence of vaccine-preventable disease.     

Texture detection of simulated microcalcification susceptibility effects in magnetic resonance imaging of breasts

The presence, size, structure and clustering characteristics of microcalcifications can indicate breast cancer. The magnetic susceptibility of microcalcifications differs from soft biological tissues, leading to directional blurring effects that can be detected by statistical image processing methods. A study of the ability of statistical texture analysis to detect simulated localized blurring in magnetic resonance imaging (MRI) of dense breast is presented. This method can detect localized blurring with sensitivity of 88.89% to 94.44%, specificity of 99.72% to 100%, positive predictive value of 73.91% to 100% and negative predictive value of 99.91% to 99.95%. J. Magn. Reson. Imaging 2001;13:876-881.     

Adaptive anisotropic gaussian filtering to reduce acquisition time in cardiac diffusion tensor imaging

Diffusion tensor imaging (DTI) is used to quantify myocardial fiber orientation based on helical angles (HA). Accurate HA measurements require multiple excitations (NEX) and/or several diffusion encoding directions (DED). However, increasing NEX and/or DED increases acquisition time (TA). Therefore, in this study, we propose to reduce TA by implementing a 3D adaptive anisotropic Gaussian filter (AAGF) on the DTI data acquired from ex-vivo healthy and infarcted porcine hearts. DTI was performed on ex-vivo hearts [9-healthy, 3-myocardial infarction (MI)] with several combinations of DED and NEX. AAGF, mean (AVF) and median filters (MF) were applied on the primary eigenvectors of the diffusion tensor prior to HA estimation. The performance of AAGF was compared against AVF and MF. Root mean square error (RMSE), concordance correlation-coefficients and Bland–Altman’s technique was used to determine optimal combination of DED and NEX that generated the best HA maps in the least possible TA. Lastly, the effect of implementing AAGF on the infarcted porcine hearts was also investigated. RMSE in HA estimation for AAGF was lower compared to AVF or MF. Post-filtering (AAGF) fewer DED and NEX were required to achieve HA maps with similar integrity as those obtained from higher NEX and/or DED. Pathological alterations caused in HA orientation in the MI model were preserved post-filtering (AAGF). Our results demonstrate that AAGF reduces TA without affecting the integrity of the myocardial microstructure.     

Automated on-the-fly detection and correction procedure for EPR imaging data acquisition.

Fast and reliable data acquisition is a major requirement for successful and useful biological electron paramagnetic resonance imaging (EPRI) experiments. Even a technologically advanced and professionally supervised EPRI system can exhibit instabilities initiated by perturbations such as animal motion, microphonics, and temperature changes. As a result, part of an acquired data set may become corrupted with excessive noise and distortions, which in turn may degrade the quality of the reconstructed image. In this work an automated scheme to monitor the system performance and stability over the course of an experiment is demonstrated. This method ensures that the quality of the acquired data is maintained during the experiment. For this purpose, four parameters including noise content and integration of each acquired projection are quantified and measured against those of the zero-gradient (ZG) projection, which is set as a quality benchmark. Projections with parameter values that differ substantially from the expected values are identified as damaged and consequently are reacquired. Therefore, the proposed technique not only effectively monitors the quality of acquisition, it also saves a substantial amount of acquisition time because it eliminates the necessity of repeating the entire experiment in cases in which only a small fraction of the data are corrupted.     

Spontaneous regression of Friend murine leukemia virus-induced erythroleukemia. IV. Effects of radiation and athymia on leukemia regression in mice.

The spontaneous regression of the erythroleukemia induced by the regressing Friend murine leukemia virus (F-MuLV) complex was inhibited by irradiation of the animals prior to F-MuLV inoculation. This inhibition was proportional to the dose of radiation used. Treatment of the mice with the bone-seeking isotope 89Sr also inhibited erythroleukemia regression, which implicates the same effector mechanisms involved in the resistance to F-MuLV or F-MuLV-induced immunosuprression. Erythroleukemias induced in athymic nude mice by the regressing F-MuLV complex exhibited higher rates of lethality than did the leukemias in heterozygous or homozygous thymus gland-containing controls. These data suggested the involvement of the immune system in erythroleukemia regression and the specific participation of thymus cells and an 89Sr-susceptible function, perhaps marrow-dependent cells, in the process of regression.