State-Level Immunization Information Systems: Potential for Childhood Immunization Data Linkages

Approximate maximum likelihood estimation in cure models using aggregated data, with application to HPV vaccine completion

Research into vaccine hesitancy is a critical component of the public health enterprise, as rates of communicable diseases preventable by routine childhood immunization have been increasing in recent years. It is therefore important to estimate proportions of "never-vaccinators" in various subgroups of the population in order to successfully target interventions to improve childhood vaccination rates. However, due to privacy issues, it may be difficult to obtain individual patient data (IPD) needed to perform the appropriate time-to-event analyses: state-level immunization information services may only be willing to share aggregated data with researchers. We propose statistical methodology for the analysis of aggregated survival data that can accommodate a cured fraction based on a polynomial approximation of the mixture cure model log-likelihood function relying only on summary statistics. We study the performance of the method through simulation studies and apply it to a real-world data set from a study examining reminder/recall approaches to improve human papillomavirus (HPV) vaccination uptake. The proposed methods may be generalized for use when there is interest in fitting complex likelihood-based models but IPD is unavailable due to data privacy or other concerns.

Reliability of information recorded on the National Immunization Program Information System

OBJECTIVE

To analyze the reliability of records held on the National Immunization Program Information System (SI-PNI) in a subsample of children included in the national vaccination coverage survey in Brazilian state capitals and Federal District in 2020.

METHODS

This was a study of agreement between data recorded on vaccination cards (doses and dates) and on the SI-PNI for 4050 children with full coverage at 24 months.

RESULTS

Data on 3587 children were held on the SI-PNI, with losses of 11% (95%CI: 10;12). Total agreement between doses and dates in the two sources was 86% (95%CI: 86;87), however taking each dose and vaccine individually, variation was greater, with 32% of data in only one source.

CONCLUSION

Part of the information was not recorded, but the discrepancy can be considered small. Nonetheless, underrecording of doses and children can compromise vaccination coverage estimates, altering the numerator and denominator data.

MAIN RESULTS

Subsample of 4,050 children, among those completing the full schedule at 24 months studied in the national survey, 11% had not been recorded on the SI-PNI, 32% had unrecorded doses (doses or dates) and there was 8% disagreement between vaccination cards and SI-PNI records.

IMPLICATIONS FOR SERVICES

Recognizing the difficulties faced by the SI-PNI and the discrepancies between sources is essential for adopting initiatives to improve data quality, so as to avoid inaccurate estimates of childhood vaccination coverage.

PERSPECTIVES

This study is expected to contribute to improving the quality of records and the usability of data for monitoring vaccination coverage of the immunization program from the local to the national level.

Immunization Information Systems

Immunization (IZ) information systems (IISs) are confidential, computerized, population-based systems that collect and consolidate IZ data from vaccination providers. The American Academy of Pediatrics continues to support the development and implementation of IISs as a beneficial tool to provide quality health care for children. Since the last revision of the American Academy of Pediatrics policy statement on IISs in 2006, numerous public health events and new data demonstrate the importance and value of these systems in society and expand the functionality and benefits of IISs beyond the basic IZ database intended to improve childhood IZ rates. This policy statement update will describe additional functions and benefits of IISs, as well as persistent and novel challenges and barriers that these systems face and pose to practicing pediatricians. Pediatricians and other pediatric health care practitioners should be aware of the value of IISs to society, the incentives and barriers involved in incorporating IIS access into a medical practice, and the opportunities to improve IISs and their functionality and usability in daily pediatric practice.

Implementation of a provider-focused intervention for maximizing human papillomavirus (HPV) vaccine uptake in young cancer survivors receiving follow-up care in pediatric oncology practices: protocol for a cluster-randomized trial of the HPV PROTECT intervention

BACKGROUND

Childhood cancer survivors are at high risk for developing new cancers (such as cervical and anal cancer) caused by persistent infection with the human papillomavirus (HPV). HPV vaccination is effective in preventing the infections that lead to these cancers, but HPV vaccine uptake is low among young cancer survivors. Lack of a healthcare provider recommendation is the most common reason that cancer survivors fail to initiate the HPV vaccine. Strategies that are most successful in increasing HPV vaccine uptake in the general population focus on enhancing healthcare provider skills to effectively recommend the vaccine, and reducing barriers faced by the young people and their parents in receiving the vaccine. This study will evaluate the effectiveness and implementation of an evidence-based healthcare provider-focused intervention (HPV PROTECT) adapted for use in pediatric oncology clinics, to increase HPV vaccine uptake among cancer survivors 9 to 17 years of age.

METHODS

This study uses a hybrid type 1 effectiveness-implementation approach. We will test the effectiveness of the HPV PROTECT intervention using a stepped-wedge cluster-randomized trial across a multi-state sample of pediatric oncology clinics. We will evaluate implementation (provider perspectives regarding intervention feasibility, acceptability and appropriateness in the pediatric oncology setting, provider fidelity to intervention components and change in provider HPV vaccine-related knowledge and practices [e.g., providing vaccine recommendations, identifying and reducing barriers to vaccination]) using a mixed methods approach.

DISCUSSION

This multisite trial will address important gaps in knowledge relevant to the prevention of HPV-related malignancies in young cancer survivors by testing the effectiveness of an evidence-based provider-directed intervention, adapted for the pediatric oncology setting, to increase HPV vaccine initiation in young cancer survivors receiving care in pediatric oncology clinics, and by procuring information regarding intervention delivery to inform future implementation efforts. If proven effective, HPV PROTECT will be readily disseminable for testing in the larger pediatric oncology community to increase HPV vaccine uptake in cancer survivors, facilitating protection against HPV-related morbidities for this vulnerable population.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT04469569, prospectively registered on July 14, 2020.

Factors associated with HPV vaccination initiation among United States college students

Human papillomavirus (HPV) remains the most common sexually transmitted infection (STI) in the U.S. despite widespread availability of a safe, effective vaccine. Although young adults are at greatest risk of HPV infection, extensive vaccine promotion and intervention efforts has been directed toward 11-12-year-olds. College students represent an ideal audience for HPV vaccine "catch-up;" however, research indicates inconsistent HPV vaccination rates within this demographic. An online survey assessing HPV and HPV vaccine knowledge and behaviors was distributed to all undergraduate college students at a large, public university in the Deep South region of the U.S. The primary outcome was receipt of HPV vaccination (binary response options of Yes/No). Logistic regression analyses were performed to determine predictors of HPV vaccination. Of the 1,725 who completed the survey, 47.0% reported having received at least one dose of HPV vaccine; overall series completion (series = 3 doses for this population) was 17.4%. The primary outcome was HPV initiation among college students, defined as having received at least one dose of the HPV vaccine. Results indicated substantial gaps in participants' knowledge of their vaccination status. Provider and parental recommendations as well as social influences were shown to significantly impact student vaccination status, emphasizing the importance of incorporating these elements in future interventions, potentially as multi-level strategies. Future college interventions should address HPV and vaccination knowledge and the importance of provider and parental recommendations.

Area-Level Variation and Human Papillomavirus Vaccination among Adolescents and Young Adults in the United States: A Systematic Review

Understanding how human papillomavirus (HPV) vaccination coverage varies by geography can help to identify areas of need for prevention and control efforts. A systematic review of the literature was conducted using a combination of keywords (HPV vaccination, geography, neighborhoods, and sociodemographic factors) on Medline and Embase databases. Studies had to provide information on HPV vaccination by area-level variables, be conducted in the United States, and be published in English (analyzing data from January 2006 to February 2020). Conference abstracts and opinion pieces were excluded. Of 733 records identified, 25 were included for systematic review. Across studies, the average initiation rate was 40.5% (range, 6.3%-78.0%). The average rate of completion was 23.4% (range, 1.7%-55.2%). Geographic regions and area-level factors were associated with HPV vaccination, including zip code tabulation area-level poverty, urbanicity/rurality, racial/ethnic composition, and health service region characteristics. Only three studies utilized geospatial approaches. None accounted for geospatial-temporal associations. Individual-level and area-level factors and their interactions are important for characterizing HPV vaccination. Results demonstrate the need to move beyond existing multilevel methods and toward the adoption of geospatial approaches that allow for the mapping and detection of geographic areas with low HPV vaccination coverage.

Practice-, provider- and patient-level facilitators of and barriers to HPV vaccine promotion and uptake in Georgia: a qualitative study of healthcare providers' perspectives

Georgia experiences higher human papillomavirus (HPV)-associated cancer burden and lower HPV vaccine uptake compared with national estimates. Using the P3 model that concomitantly assesses practice-, provider- and patient-level factors influencing health behaviors, we examined facilitators of and barriers to HPV vaccine promotion and uptake in Georgia. In 2018, we conducted six focus groups with 55 providers. Questions focused on multilevel facilitators of and barriers to HPV vaccine promotion and uptake. Our analysis was guided by the P3 model and a deductive coding approach. We found that practice-level influences included organizational priorities of vaccinations, appointment scheduling, immunization registries/records, vaccine availability and coordination with community resources. Provider-level influences included time constraints, role, vaccine knowledge, self-efficacy to discuss HPV vaccine and vaccine confidence. Patient-level influences included trust, experiences with vaccine-preventable diseases, perceived high costs, perceived side effects and concerns with sexual activity. Findings suggest that interventions include incentives to boost vaccine rates and incorporate appointment scheduling technology. An emphasis should be placed on the use of immunization registries, improving across-practice information exchange, and providing education for providers on HPV vaccine. Patient-provider communication and trust emerge as intervention targets. Providers should be trained in addressing patient concerns related to costs, side effects and sexual activity.

Redefining vaccination coverage and timeliness measures using electronic immunization registry data in low- and middle-income countries

Vaccine coverage is routinely used as a performance indicator for immunization programs both at local and global levels. For many national immunization programs, there are challenges with accurately estimating vaccination coverage based on available data sources, however an increasing number of low- and middle-income countries (LMICs) have begun implementing electronic immunization registries to replace health facilities’ paper-based tools and aggregate reporting systems. These systems allow for more efficient capture and use of routinely reported individual-level data that can be used to calculate dose-specific and cohort vaccination coverage, replacing the commonly used aggregate routine health information system data. With these individual-level data immunization programs have the opportunity to redefine performance measures to enhance programmatic decision-making at all levels of the health system. In this commentary, we discuss how measures for assessing vaccination status and program performance can be redefined and recalculated using these data when generated at the health facility level and the implications of the use and availability of electronic individual-level data.

Assessing the effectiveness of high-dose influenza vaccine in preventing hospitalization among seniors, and observations on the limitations of effectiveness study design

BACKGROUND

The availability of high-dose (HD) influenza vaccine for seniors should decrease influenza-related hospitalization. Studies to date show a range of mostly moderate increased HD vaccine effectiveness (VE). While a 'healthy vaccinee' phenomenon can inflate VE, for influenza and particularly an HD vaccine targeted at frailer adults, an 'at-risk vaccinee' bias may deflate VE estimates. We assessed senior HD vaccine effectiveness against influenza-related hospitalization by linking immunization registry records to hospitalizations. We also examined whether adding strata typically ignored in case-control matching schemas, such as residence areas, exact age, and provider biases, would increase VE.

METHODS

For the 2016-17 influenza season in the Portland metropolitan area, the differential VE for the HD vaccine in preventing PCR-confirmed influenza hospitalization was assessed by a nested series of models across matching strata. For an exact match for high-dose and standard-dose seniors, matching elements included exact age, gender, residence type, race-ethnicity, provider bias, and residence area (zipcode).

RESULTS

As a first step, a simple aggregate comparison of influenza-related hospitalization risk showed no added HD effectiveness. For the nested models, adding strata increased VE. In the final model, among 23,712 matched pairs of HD to SD vaccinated seniors, the HD vaccine was 30.7% (95%CI: 8-48%) more effective in preventing influenza-related hospitalization.

CONCLUSION

For this study, the high-dose influenza vaccine provided superior protection for seniors against influenza hospitalization. Including matching elements as exact year of age and residence zipcode all added to the calculation of VE. As a warning, non-matched or overly simple matched VE study designs may substantially under-estimate VE.

Assessing Potential Confounding and Misclassification Bias When Studying the Safety of the Childhood Immunization Schedule

OBJECTIVES

Some parents are concerned the childhood immunization schedule could increase risk for allergic disorders, including asthma. To inform future safety studies of this speculated association, a parent survey was conducted to examine the risk of misclassification of vaccination status in electronic health record data, and to assess the potential for confounding if asthma risk factors varied by vaccination status.

METHODS

A survey was conducted among parents of children 19 to 35 months old at 6 medical organizations within the Vaccine Safety Datalink. Parents of children in 4 vaccination groups were surveyed: 1) no vaccines by 12 months of age and a diagnosis of parental vaccine refusal; 2) consistent vaccine limiting (≤2 vaccines per visit); 3) not consistently vaccine limiting but otherwise undervaccinated with a vaccine refusal diagnosis; and 4) fully vaccinated with no delays and no vaccine refusal. Parents were surveyed about their child's vaccination status and whether asthma risk factors existed.

RESULTS

Among a survey sample of 2043 parents, 1209 responded (59.2%). For receiving no vaccines, the observed agreement between parent report and electronic health record data was 94.0% (κ = 0.79); for receiving all vaccines with no delays, the observed agreement was 87.3% (κ = 0.73). Although most asthma risk factors (allergic rhinitis, eczema, food allergies, family asthma history) reported by parents did not differ significantly between children in the vaccination groups studied, several factors (aeroallergen sensitivity, breastfeeding) differed significantly between groups.

CONCLUSIONS

Measurement and control of disease risk factors should be carefully considered in observational studies of the safety of the immunization schedule.

Assessing misclassification of vaccination status: Implications for studies of the safety of the childhood immunization schedule

BACKGROUND

To address public concern about the safety of the childhood immunization schedule, the Institute of Medicine recommended observational studies comparing adverse health outcomes of fully vaccinated children to children under-vaccinated due to parental choice. Misclassification of vaccination status could bias such studies.

OBJECTIVE

To assess risk of misclassification of vaccination status within the Vaccine Safety Datalink (VSD).

DESIGN/METHODS

A retrospective cohort study was conducted in three phases. In phase 1, electronic health record (EHR) data were used to identify patterns of under-vaccination during the first 24months of life potentially due to parental choice. In phase 2, a random sample of records of under-vaccinated children was manually reviewed. In phase 3, a separate sample of parents were surveyed to assess whether EHR data accurately reflected their child's vaccination status. Phases 1 and 2 were conducted at 6 VSD sites, phase 3 at 1 site.

RESULTS

The study cohort included 361,901 children born 2004 through 2012. By 24months of age, 198,249 (54.8%) were fully vaccinated with no delays, 84,698 (23.4%) experienced delays but were fully vaccinated by 24months of age, 4865 (1.3%) received no vaccines, 3789 (1.0%) delayed starting vaccination until ≥4months of age, 4781 (1.3%) had consistent vaccine-limiting (≤2 vaccines per visit), and the remaining 65,519 (18.1%) were missing vaccine series or doses. When a diagnosis code for vaccine refusal was present in EHR data, encounter notes confirmed vaccine refusal as the reason for under-vaccination for nearly 100% of sampled records. Parent surveys confirmed these findings. Parents of under-vaccinated children were more likely to report visiting an alternative medical provider than parents of fully vaccinated children.

CONCLUSIONS

Specific groups of children, under-vaccinated due to parental choice, can be identified with relatively low likelihood of misclassification of vaccination status using EHR-based vaccine data and diagnosis codes.