Examining the spatiotemporal evolution of vaccine refusal: nonmedical exemptions from vaccination in California, 2000-2013

Association of Type of Vaccination Center With Time to Emergency Department Presentation for Acute COVID-19 Infection: An Exploratory Analysis

Objective The objective of this study was to identify potential associations between coronavirus disease 2019 (COVID-19) vaccination center reception location and time to presentation to the emergency department for acute COVID-19 infection. The a priori hypothesis was that there are significant differences in the outcome based on vaccination administration center type. Methods This was a cross-sectional, observational study conducted within a hospital in Lakeland, Florida, between October 2021 and May 2022. Participants were at least 18 years old with confirmed severe acute respiratory syndrome coronavirus 2 (SARS‑CoV‑2) infection and at least two COVID-19 symptoms at enrollment. Patients with prior confirmed COVID-19 diagnosis and hospitalization within 10 days of screening were excluded. Participants were sampled from within the emergency department of the institution. The primary outcome was time to presentation to the emergency department for acute COVID-19 infection since the last vaccination dose from each sampled COVID-19 vaccination center location. Results A total of 93 participants were analyzed. Of these, 48 (52%) participants received COVID-19 vaccination. Participants vaccinated at vaccine clinics demonstrated a significantly longer mean survival time (288.2 (29.9)) compared to other sites. Significant predictors of hospitalization were age (aOR, 1.09, 95%CI 1.02-1.16, p < 0.01), sex (aOR: 10.05, 95%CI 1.52-66.54, p < 0.05), physical function (aOR, 0.90, 95%CI 0.83-0.97, p < 0.01) and number of medications (aOR, 1.34, 95%CI 1.14-1.58, p < 0.001).  Conclusions This exploratory analysis highlights the need for further investigation into both characteristics of healthcare institutions and individual-level factors that may play a role in the prolonged prevention of emergency department presentations due to COVID-19 infection. Increased transparency of data regarding practices related to the administration of COVID-19 vaccines across various institutions may be beneficial in further understanding the role of COVID-19 vaccinations in preventing symptomatic disease across local and global communities.

Exploring the impact of the New York State repeal of nonmedical vaccination exemptions on student enrollment, absenteeism, and school workload: Perspectives from a survey of school administrators

In June 2019, New York State (NYS) adopted Senate Bill 2994A eliminating nonmedical vaccine exemptions from school entry laws. Since student noncompliance with the law required school exclusion, we sought to evaluate the law's effects on student enrollment and absenteeism, and school workloads related to its implementation. In November 2019, we sent an electronic survey to NYS (excluding New York City) schools. Due to the COVID-19 pandemic, outreach was curtailed in March 2020 with 525 (14%) of 3,759 eligible schools responding. To account for non-response, results were analyzed using inverse probability weighting. After weighting, 39% (95% CI: 34%, 44%) of schools reported enrollment changes and 31% (95% CI: 26%, 36%) of schools reported absenteeism related to the law. In addition, 95% (95% CI: 93%, 98%) of schools reported holding meetings and/or preparing correspondence about the law, spending a mean of 14 (95% CI: 11, 18) hours on these communication efforts. Schools in the highest pre-mandate nonmedical exemption tertile (vs. lowest) were more likely to report enrollment and absenteeism changes, and higher workloads. While our results should be interpreted with caution, changes in student enrollment, absenteeism, and school workloads may represent important considerations for policymakers planning similar legislation.

State Policy Removing the Personal Belief Exemption for Measles, Mumps, and Rubella (MMR) School Immunization Requirement, Washington State, 2014-2022

Objectives. To assess the impact of Washington State's 2019 Engrossed House Bill (EHB) 1638-which removed measles, mumps, and rubella (MMR) personal belief exemptions-on MMR vaccine series completion and exemption rates in K-12 students. Methods. We used interrupted time-series analyses to examine changes in MMR vaccine series completion rates before and after EHB 1638 was passed and the χ2 test for differences in exemption rates. Results. EHB 1638 implementation was associated with a 5.4% relative increase in kindergarten MMR vaccine series completion rates (95% confidence interval = 3.8%, 7.1%; P ≤ .001), and results were similar with Oregon as a control state (no change observed in Oregon; P = .68). MMR exemptions overall decreased 41% (from 3.1% in 2018-2019 to 1.8% in 2019-2020; P ≤ .001), and religious exemptions increased 367% (from 0.3% to 1.4%; P ≤ .001). Conclusions. EHB 1638 was associated with an increase in MMR vaccine series completion rates and a decrease in any MMR exemption. However, effects were partially offset by an increase in religious exemption rates. Public Health Implications. Removal of personal belief exemptions for the MMR immunization requirement only may be an effective approach to increase MMR vaccine coverage rates statewide and among underimmunized communities. (Am J Public Health. 2023;113(7):795-804. https://doi.org/10.2105/AJPH.2023.307285).

Missed Vaccination Opportunities Among U.S. Adolescents by Area Characteristics

INTRODUCTION

A total of 3 vaccines are recommended for U.S. adolescents: tetanus, diphtheria, and acellular pertussis; meningococcal conjugate; and human papillomavirus. To understand the disparities in vaccine availability and hesitancy, adolescent-, household-, and area-level characteristics associated with patterns of vaccine coverage are described.

METHODS

In 2020-2021, the authors generated national estimates among 8 possible combinations of vaccine coverage and identified the associated characteristics using 2015-2017 National Immunization Survey-Teen for male and female adolescents aged 13-17 years (N=63,299) linked to area (ZIP code) characteristics. Next, the factors associated with a missed opportunity for human papillomavirus vaccine (i.e., receipt of tetanus, diphtheria, and acellular pertussis and meningococcal conjugate only compared with coverage of all the 3 vaccines) were identified using logistic regression.

RESULTS

Most U.S. adolescents received all the 3 vaccines (42.9%) or tetanus, diphtheria, and acellular pertussis and meningococcal conjugate only (32.1%); fewer received no vaccines (7.7%) or tetanus, diphtheria, and acellular pertussis only (6.6%); and the remainder received some combination of 1-2 vaccines. Missed opportunities for human papillomavirus vaccination were more likely among adolescents who were male, were of White race, were uninsured, were in middle-income households, and were living in rural areas and were less likely among adolescents who were older, who were Medicaid insured, whose parents completed surveys in Spanish, who were in poverty-level households, and who were living in high-poverty areas.

CONCLUSIONS

A substantial number of U.S. adolescents are not fully vaccinated, and coverage varies by vaccine type, population, and place. Providers should routinely stock all the 3 vaccines and promote simultaneous, same-day vaccination to avoid missed vaccine opportunities. More research and interventions are needed to understand and modify patient, provider, payer, vaccine supply/storage, or other reasons for suboptimal coverage of all the recommended vaccines.

A pre-vaccine analysis using the Health Belief Model to explain parents' willingness to vaccinate (WTV) their children in the United States: implications for vaccination programs

BACKGROUND

This study uses the Health Belief Model (HBM) to explain parents' willingness-to-vaccinate (WTV) their children with COVID-19 vaccine in the United States (US). Analysis included determining if vaccination choice among parents statistically varied based on geography among the sample collected.

METHODS

A cross-sectional survey was administered November 2020. Multiple regression analysis was completed determining which HBM constructs to be most relevant to parents' WTV their children with COVID-19 vaccine. To determine "hot" and "cold" geographic spots for WTV, a hot spot analysis based on Getis-Ord Gi* statistics was executed.

RESULTS

Primary data collection included a convenience sample of US parents. Approximately 66% of parents surveyed were "likely/extremely likely" to vaccinate their children if the COVID-19 vaccine was provided free by the government. Results highlight HBM connections to WTV.

CONCLUSIONS

The relationship between parents' WTV their children with a COVID-19 vaccine and constructs within the theoretical framework of the HBM represents a necessary point in the development of efficacious COVID-19 vaccination programs among parents in the US. Interpreting differences in location and health beliefs toward vaccines merit in-depth investigation for local, state and federal level vaccination programs to be effective.

Spatial Clustering of Vaccine Exemptions on the Risk of a Measles Outbreak

OBJECTIVES

Areas of increased school-entry vaccination exemptions play a key role in epidemics of vaccine-preventable diseases in the United States. California eliminated nonmedical exemptions in 2016, which increased overall vaccine coverage but also rates of medical exemptions. We examine how spatial clustering of exemptions contributed to measles outbreak potential pre- and postpolicy change.

METHODS

We modeled measles transmission in an empirically calibrated hypothetical population of youth aged 0 to 17 years in California and compared outbreak sizes under the observed spatial clustering of exemptions in schools pre- and postpolicy change with counterfactual scenarios of no postpolicy change increase in medical exemptions, no clustering of exemptions, and lower population immunization levels.

RESULTS

The elimination of nonmedical exemptions significantly reduced both average and maximal outbreak sizes, although increases in medical exemptions resulted in more than twice as many infections, on average, than if medical exemptions were maintained at prepolicy change levels. Spatial clustering of nonmedical exemptions provided some initial protection against random introduction of measles infections; however, it ultimately allowed outbreaks with thousands more infections than when exemptions were randomly distributed. The large-scale outbreaks produced by exemption clusters could not be reproduced when exemptions were distributed randomly until population vaccination was lowered by >6 percentage points.

CONCLUSIONS

Despite the high overall vaccinate rate, the spatial clustering of exemptions in schools was sufficient to threaten local herd immunity and reduce protection from measles outbreaks. Policies strengthening vaccine requirements may be less effective if alternative forms of exemptions (eg, medical) are concentrated in existing low-immunization areas.

Revisiting the 2014-15 Disneyland measles outbreak and its influence on pediatric vaccinations

The 2014-15 Disneyland measles outbreak that began at the California theme park in December 2014 sparked an international conversation regarding measles, vaccine hesitancy, and vaccine policies. The outbreak capped a year with the highest number of measles cases reported in two decades and came amidst increasing trends in nonmedical vaccine exemptions in California and elsewhere. Because of its sensational story line and spread among unvaccinated populations, the outbreak received a high level of media coverage that focused on vaccine hesitancy as a primary driver of the outbreak. This media coverage and the ostensible public support for vaccines that followed led some to hypothesize that the outbreak might have a "Disneyland effect," or a positive influence on the uptake of pediatric measles vaccine. This article reviews the facts of the outbreak and its context, and explores the evidence for the Disneyland outbreak causing an influence on U.S. pediatric vaccine-related beliefs and behaviors.

Evaluating Michigan's Administrative Rule Change on Nonmedical Vaccine Exemptions

OBJECTIVES

Vaccine hesitancy is a growing threat to health in the United States. Facing the fourth highest vaccine exemption rate in the United States in 2014, Michigan changed its state Administrative Rules, effective January 1, 2015, requiring parents to attend an in-person vaccine education session at their local health department before obtaining a nonmedical exemption (NME). In this article, we evaluate the longer-term impact of this policy change on the rate, spatial distribution, and sociodemographic predictors of NMEs in Michigan.

METHODS

Using school-level kindergarten vaccination data from Michigan from 2011 to 2018, we evaluated sociodemographic predictors of NMEs before and after this Administrative Rule change using Bayesian binomial regression. We measured the persistence and location of school district-level geographic clustering using local indicators of spatial association.

RESULTS

Immediately after the rule change, rates of NMEs fell by 32%. However, NME rates rebounded in subsequent years, increasing by 26% by 2018, although income disparities in NME rates decreased after the rule change. Philosophical, religious, and medical vaccine exemptions exhibited distinct geographic patterns across the state, which largely persisted after 2015, illustrating that NME clusters remain a concern despite this rule change.

CONCLUSIONS

Although Michigan's Administrative Rule change caused a short-term decline in NME rates, NME rates have risen dramatically in the following 4 years since the policy was implemented. Michigan's administrative effort to require parental education at the local health department before receiving an exemption did not cause a sustained reduction in the rate or spatial distribution of NMEs.

Spatial-temporal patterns of childhood immunization in New Zealand (2006-2017): an improving pattern but not for all?

BACKGROUND

Declining childhood immunization represents a serious public health problem globally and in New Zealand. To guide efforts to increase immunization coverage, this study monitors nationwide change in immunization coverage since the introduction of the National Immunisation Register (NIR) in 2005 and spatiotemporal patterns of immunization coverage from 2006 to 2017.

METHODS

The study population consisted of 4 482 499 individual immunization records that were obtained from the NIR (2005-2017). Data on yearly and average immunization coverage in census area units (CAUs) in New Zealand were calculated by milestone age (6/8/12/18/24/60/144 months). Data for 2005 were excluded due to missing records in the introductory period of the NIR. We analyzed spatial and spatiotemporal patterns using Gi* and SaTScan methods.

RESULTS

Immunization coverage improved since the introduction of the NIR in 2005, reaching a peak in 2014 and 2015 with a slight decrease in 2016 and 2017. Well and insufficiently immunized areas were identified with spatial autocorrelation analyses highlighting several hot- and cold-spots. Comparison of CAUs with neighbouring CAUs allowed for the identification of places where immunization coverage was significantly higher or lower than expected, over both time and space.

CONCLUSION

We provide the first spatiotemporal analysis of childhood immunization in New Zealand that utilizes a large sample of over 4.4 million individual immunization records. Our spatial analyses enable policymakers to understand the development of childhood immunization coverage and make more effective prevention strategies in New Zealand.

Measuring Multiple Dimensions and Indices of Nonvaccination Clustering in Michigan, 2008-2018

Michigan experienced a significant measles outbreak in 2019 amidst rising rates of nonmedical vaccine exemptions (NMEs) and low vaccination coverage compared with the rest of the United States. There is a critical need to better understand the landscape of nonvaccination in Michigan to assess the risk of vaccine-preventable disease outbreaks in the state, yet there is no agreed-upon best practice for characterizing spatial clustering of nonvaccination, and numerous clustering metrics are available in the statistical, geographical, and epidemiologic literature. We used school-level data to characterize the spatiotemporal landscape of vaccine exemptions in Michigan for the period 2008-2018 using Moran's I, the isolation index, the modified aggregation index, and the Theil index at 4 spatial scales. We also used nonvaccination thresholds of 5%, 10%, and 20% to assess the bias incurred when aggregating vaccination data. We found that aggregating school-level data to levels commonly used for public reporting can lead to large biases in identifying the number and location of at-risk students and that different clustering metrics yielded variable interpretations of the nonvaccination landscape in Michigan. This study shows the importance of choosing clustering metrics with their mechanistic interpretations in mind, be it large- or fine-scale heterogeneity or between- and within-group contributions to spatial variation.

[Geographic analyses as a foundation for evidence-based public health interventions: the example identification and typology of risk clusters for mumps, measles, and rubella]

BACKGROUND

Ideally, health services and interventions to improve immunization rates should be tailored to local target populations, such as spatial clusters. However, to date, little attention has been paid to spatial clusters of underimmunization and have instead been typified based on small-scale data.

AIM

Using the example of vaccination against measles, mumps, and rubella (MMR) in children, the present study aims to (1) identify the spatial distribution of insufficient MMR vaccination in Westphalia-Lippe on a small scale, (2) identify specific, spatial risk clusters with insufficient vaccination protection, and (3) describe spatial-neighborhood influencing factors of the different risk clusters as starting points for public health interventions.

MATERIAL AND METHODS

Account data from the Kassenärztliche Vereinigung Westfalen-Lippe (KVWL) were used as a basis. Birth cohorts 2013-2016 of children with statutory health insurance were formed and aggregated at postcode level (n = 410). Statistically significant, spatially compact clusters and relative risks (RRs) of underimmunization were identified. Local risk models were estimated in binary logistic regressions based on spatial-neighborhood variables.

RESULTS AND DISCUSSION

Two significant clusters of underimmunization were identified for each of the vaccination rates "at least one MMR vaccination" and "both MMR vaccinations." Significant risk factors for low immunization rates included age structure, socioeconomic variables, population density, medical coverage, and value attitude. The proposed methodology is suitable for describing spatial variations in vaccination behavior based on identified typologies for targeted evidence-based interventions.

In the Wake of a Pandemic: Revisiting School Approaches to Nonmedical Exemptions to Mandatory Vaccination in the US

Mandatory school vaccination policies with exclusion of unvaccinated students can be a powerful tool in ensuring high vaccination rates. Some parents may object to mandatory vaccination policies, claiming exemptions based on medical, religious, or philosophical reasons. Individual schools, school systems, or local or regional governments have different policies with respect to whether, and what kind of, exemptions may be allowed. In the setting of the current pandemic, questions regarding the acceptability of exemptions have resurfaced, as schools and local governments struggle with how to safely return children to school. Anticipating that school attendance will be facilitated by the development of a vaccine, school systems will face decisions about whether to mandate vaccination and whether to permit exemptions. The American Academy of Pediatrics promulgates policy favoring the elimination of nonmedical exemptions generally in schools. This discussion considers whether schools should eliminate nonmedical exemptions to vaccination as proposed in the American Academy of Pediatrics policy, ultimately concluding that broad elimination of exemptions is not justified and advocating a more nuanced approach that encourages school attendance while promoting vaccination and broader public health goals.

The geographic distribution of un-immunized children in Ontario, Canada: Hotspot detection using Bayesian spatial analysis

BACKGROUND

In Ontario, Canada, little is currently known about the extent to which un-immunized children may cluster geographically. Our objectives were to: describe the geographic distribution of fully un-immunized children; identify geographic clusters (hotspots) of un-immunized children; and to characterize the contribution of spatial effects and covariates on hotspots, where found.

METHODS

Our analytic cohort consisted of Ontario students aged 7-17 years in the 2016-2017 school year. We defined students as un-immunized if they had zero doses of any vaccine and a non-medical exemption recorded in Ontario's registry. We calculated unadjusted proportions of un-immunized students by Census Subdivision (CSD) and then used a sequential approach to identify hotspots starting first with hotspot identification at the CSD level and then probed identified hotspots further by Dissemination Area (DA) and including covariates. Hotspots were identified using the Besag-York-Mollie Bayesian spatial model and were defined as areas with >95% probability of having two times the proportion of un-immunized students, relative to the province overall.

RESULTS

We identified 15,208 (0.94%) un-immunized children within our cohort consisting of more than 1.61 million students. Unadjusted proportions of un-immunized students varied greatly by geography, ranging from 0% to 21.5% by CSD. We identified 16 hotspot CSDs which clustered in five distinct areas, all of which were located in southern Ontario. The contribution of covariates and spatial effects on the risk of having un-immunized students varied greatly across hotspot areas.

CONCLUSIONS

Although the provincial proportion (0.94%) of un-immunized students is small, geographical clustering of such students is evident in Ontario and in some areas presents an important risk for future outbreaks. Further qualitative work within these hotspot areas would be a helpful next step to better characterize the factors associated with vaccine refusal in these communities.

Fine-scale spatial clustering of measles nonvaccination that increases outbreak potential is obscured by aggregated reporting data

The United States experienced historically high numbers of measles cases in 2019, despite achieving national measles vaccination rates above the World Health Organization recommendation of 95% coverage with two doses. Since the COVID-19 pandemic began, resulting in suspension of many clinical preventive services, pediatric vaccination rates in the United States have fallen precipitously, dramatically increasing risk of measles resurgence. Previous research has shown that measles outbreaks in high-coverage contexts are driven by spatial clustering of nonvaccination, which decreases local immunity below the herd immunity threshold. However, little is known about how to best conduct surveillance and target interventions to detect and address these high-risk areas, and most vaccination data are reported at the state-level-a resolution too coarse to detect community-level clustering of nonvaccination characteristic of recent outbreaks. In this paper, we perform a series of computational experiments to assess the impact of clustered nonvaccination on outbreak potential and magnitude of bias in predicting disease risk posed by measuring vaccination rates at coarse spatial scales. We find that, when nonvaccination is locally clustered, reporting aggregate data at the state- or county-level can result in substantial underestimates of outbreak risk. The COVID-19 pandemic has shone a bright light on the weaknesses in US infectious disease surveillance and a broader gap in our understanding of how to best use detailed spatial data to interrupt and control infectious disease transmission. Our research clearly outlines that finer-scale vaccination data should be collected to prevent a return to endemic measles transmission in the United States.

Current landscape of nonmedical vaccination exemptions in the United States: impact of policy changes

INTRODUCTION

In the United States, high childhood vaccination coverage has reduced the morbidity and mortality due to vaccine-preventable diseases. The success of vaccination programs in achieving this high coverage is due, in part, to vaccination mandates for school entry. All states have such mandates, but there is heterogeneity across the states in the allowance of non-medical exemptions (e.g. religious or personal belief exemptions) to these mandates.

AREAS COVERED

We examine historical trends in non-medical exemption prevalence in the US, discuss recent state-level policy changes that may impact non-medical exemption prevalence, and review recent studies on the association between non-medical exemptions and infectious disease outbreaks.

EXPERT COMMENTARY

State-level implementation of mandates, and related allowances for medical and non-medical exemptions, varies greatly across the United States. Non-medical exemption rates have increased over the last two decades, with an increased risk of disease outbreaks in clusters of children with non-medical exemptions due to differences in state laws. Recent efforts to address non-medical exemption rates range from incorporating additional administrative requirements for exemptions and disallowance of any non-medical exemptions. Continued monitoring is needed to evaluate the impact of these changes on exemption rates, to develop optimal childhood vaccination policy across the United States.