Immunization milestones: a more comprehensive picture of age-appropriate vaccination

Beyond Vaccination Coverage: Population-Based Measurement of Early Childhood Immunization Schedule Adherence

The immunization schedule recommended by the U.S. Advisory Committee on Immunization Practices (ACIP) provides a structure for how 10 different vaccine series should be administered to children in the first 18 months of life. Progress toward US early childhood immunization goals has largely focused on measuring vaccination coverage at age 24 months. However, standard vaccination coverage measures do not reflect whether children received vaccine doses by recommended ages, or whether vaccines were given concomitantly, per the schedule. In this paper, we describe innovations in population-level measurement of immunization schedule adherence through quantifying vaccination timeliness and undervaccination patterns. Measuring vaccination timeliness involves comparing when children received vaccine doses relative to ACIP age recommendations. To assess undervaccination patterns, children's vaccination histories are analyzed to determine whether they were vaccinated consistent with the ACIP schedule. Some patterns, such as spreading out vaccines across visits, are indicative of parental hesitancy. Other patterns, such as starting all recommended series but missing doses, are largely indicative of other immunization services delivery challenges. Since 2003, at least 12 studies have used National Immunization Survey-Child, immunization information system, or integrated health plan data to measure vaccination timeliness or undervaccination patterns at national or state levels. Moving forward, these novel measures can be leveraged for population-based surveillance of vaccine confidence, and for distinguishing undervaccination due to parental vaccine hesitancy from undervaccination due to other causes. Broader adoption of these measures can facilitate identification of targeted strategies for improving timely and routine early childhood vaccination uptake across the United States.

A National Cross-Sectional Study from the Republic of Kosovo on Lot Quality Assurance Sampling (LQAS) to Evaluate the Vaccination Status of Children Between 12 and 24 Months of Age During 2018 to 2020

BACKGROUND In the Republic of Kosovo, full vaccination status in children under age 2 years includes: 1 dose of Bacillus Calmette-Guerin (BCG) hepatitis B virus (HBV) vaccine; 3 doses of diphtheria, tetanus, pertussis, hepatitis B, polio, and Haemophilus influenzae type b (DTaP-HB-IPV-Hib) vaccine; 3 doses of inactivated polio vaccine (IPV); and 1 dose of measles, mumps, and rubella (MMR) vaccine. Lot quality assurance sampling (LQAS) is a method used to assess the performance of health quality indicators. MATERIAL AND METHODS A national cross-sectional study with children aged between 12 and 24 months from Kosovo was performed between 2018 and 2020. The vaccination status of children was assessed with lot quality assurance sampling (LQAS) using randomized samples. RESULTS Among 430 children, more than 90% had completed the full immunization schedule. Delays in children's immunizations were observed. Most vaccinations showed short delays of less than 1 month, followed by delays of up to 3 months. The main reason for vaccination delay was the COVID-19 pandemic, following by child's illness at the scheduled time of vaccination or the parents were too busy to take the child to the vaccination site. Meanwhile, child age was the only parameter that showed difference among non-vaccinated and fully vaccinated (P<0.001). CONCLUSIONS LQAS analysis showed that between 2018 and 2020 lack of full immunization was due to delay caused by the parent not taking the child to the vaccination site, which may be prevented by improving information given to parents and the use of vaccination reminders.

Timeliness of Early Childhood Vaccinations and Undervaccination Patterns in Montana

INTRODUCTION

Early childhood vaccination rates are lower in rural areas than those in urban areas of the U.S. This study's objective is to quantify vaccine timeliness and the prevalence of undervaccination patterns in Montana and to measure the associations between timeliness and series completion by age 24 months.

METHODS

Using records from January 2015 to November 2019 in Montana's centralized immunization information system, days undervaccinated were calculated for the combined 7-vaccine series. Undervaccination patterns indicative of certain barriers to vaccination, including parental vaccine hesitancy, were identified. Using multivariable log-linked binomial regression, the association between timing of vaccine delay and not completing the combined 7-vaccine series by age 24 months was assessed. Analyses were conducted in March 2020-August 2020.

RESULTS

Among 31,422 children, 38.0% received all vaccine doses on time; 24.3% received all doses, but some were received late; and 37.7% had not completed the combined 7-vaccine series. Approximately 18.7% had an undervaccination pattern suggestive of parental vaccine hesitancy, and 19.7% started all series but were missing doses needed for multidose series completion. Although falling behind on vaccinations at any age was associated with failing to complete the combined 7-vaccine series, being late at age 12-15 months had the strongest association (adjusted prevalence ratio=3.73, 95% CI=3.56, 3.91) compared with being on time at age 12-15 months.

CONCLUSIONS

Fewer than 2 in 5 Montana children were fully vaccinated on time for the combined 7-vaccine series. To increase vaccination rates, initiatives to increase vaccine confidence and remind parents to complete vaccine series are needed.

Adherence to Timely Vaccinations in the United States

OBJECTIVES

To estimate (1) the proportion of children not adhering to the Advisory Committee on Immunization Practices (ACIP) recommended early childhood immunization schedule and (2) associations between schedule adherence, sociodemographic characteristics, and up-to-date immunization status by 19 to 35 months of age.

METHODS

We used 2014 National Immunization Survey provider-verified vaccination data to classify vaccination patterns as "recommended" (ie, in line with ACIP dose- and age-specific recommendations), "alternate" (ie, in line with either limiting the number of shots per visit or skipping at least 1 vaccine series), or "unknown or unclassifiable" (ie, not in line with ACIP recommendations or clearly limiting shots per visit or vaccine series). We evaluated the association between vaccination patterns and up-to-date status for all ACIP-recommended vaccinations (including rotavirus and hepatitis A vaccines) using Poisson regression.

RESULTS

The majority of children's patterns were classified as "recommended" (63%), with 23% and 14% following alternate or unknown or unclassifiable patterns, respectively; 58% of children were up-to-date with all ACIP-recommended immunizations by 19 to 35 months. Not being up-to-date was associated with alternate (prevalence ratio = 4.2, 95% confidence interval: 3.9-4.5) and unknown or unclassifiable (prevalence ratio = 2.4, 95% confidence interval: 2.2-2.7) patterns.

CONCLUSIONS

High vaccine coverage by 19 to 35 months of age may miss nonadherence to the recommended immunization schedule in the first 18 months of life, leaving children vulnerable to preventable diseases. With more than one-third of US children not following the ACIP schedule, targeted interventions are needed to minimize vaccine delays and disease susceptibility.

Compliance with vaccination schedules

Childhood immunization is amongst the most cost-effective public health interventions for reducing children's morbidity and mortality. Vaccination coverage is commonly used to assess the vaccination status of a community. Adherence to schedule is critical for providing maximum effectiveness against vaccine-preventable diseases in the community. This is of paramount importance for diseases that are continuously circulating because they can cause large outbreaks. All stakeholders (public health administrators and vaccination providers) should work together in order to increase both vaccination coverage and adherence to schedule. They have to improve the infrastructure used for delivering vaccines, train the health care professionals and finally raise the awareness of the importance of vaccines among parents.

Gaps in Well-Child Care Attendance Among Primary Care Clinics Serving Low-Income Families

BACKGROUND AND OBJECTIVES

It is unclear which specific well-child visits (WCVs) are most frequently missed and whether age-specific patterns of attendance differ by race or insurance type.

METHODS

We conducted a retrospective cohort study of children 0 to 6 years old between 2011 and 2016 within 2 health networks spanning 20 states. WCVs were identified by using International Classification of Diseases, Ninth and 10th Revisions and Current Procedural Terminology codes. We calculated adherence to the 13 American Academy of Pediatrics-recommended WCVs from birth to age 6 years. To address data completeness, we made 2 adherence calculations after a child's last recorded WCV: 1 in which we assumed all subsequent WCVs were attended outside the network and 1 in which we assumed none were.

RESULTS

We included 152 418 children in our analysis. Most children were either publicly insured (77%) or uninsured (14%). The 2-, 4-, and 6-month visits were the most frequently attended (63% [assuming no outside care after the last recorded WCV] to 90% [assuming outside care]), whereas the 15- and 18-months visits (41%-75%) and 4-year visit (19%-49%) were the least frequently attended. Patients who were publicly insured and uninsured (versus privately insured) had higher odds of missing WCVs. Hispanic and Asian American (versus non-Hispanic white) patients had higher odds of attending WCVs.

DISCUSSION

The 15- and 18-month WCVs as well as the 4-year WCV are the least frequently attended WCVs. The former represent opportunities to identify developmental delays, and the latter represents an opportunity to assess school readiness.

Vaccination Timeliness at Age 24 Months in Michigan Children Born 2006-2010

INTRODUCTION

Delays in vaccination can stymie the development of herd immunity, and a large proportion of children in the U.S. are known not to receive vaccines on time. This study quantifies delays in vaccination, compares vaccination timeliness to the proportion of children vaccinated, and evaluates the impact of combination vaccine use and timely administration of hepatitis B vaccine birth dose on vaccine timeliness among Michigan children.

METHODS

This retrospective cohort study used data from the Michigan Care Improvement Registry-the state immunization information system-for children born 2006-2010. Children aged 24 months as of December 31, 2012, were included. The proportion of children with timely administration of vaccine doses was calculated, and the mean days of vaccination delay with SD were reported.

RESULTS

Among 620,592 Michigan children, 42.2% had received all vaccines, but only 13.2% were vaccinated on time by age 24 months. Children's vaccinations were delayed an average of 59.2 (SD=91.2) days by age 24 months for all recommended vaccine doses. Children who received a timely hepatitis B vaccine birth dose or who received a combination vaccine had less delay in vaccination.

CONCLUSIONS

Michigan children have high vaccination coverage based on standard measures but few receive these vaccines on time. Promoting use of combination vaccines may improve parental compliance with timely vaccination of children.

Immunization information systems to increase vaccination rates: a community guide systematic review

CONTEXT

Immunizations are the most effective way to reduce incidence of vaccine-preventable diseases. Immunization information systems (IISs) are confidential, population-based, computerized databases that record all vaccination doses administered by participating providers to people residing within a given geopolitical area. They facilitate consolidation of vaccination histories for use by health care providers in determining appropriate client vaccinations. Immunization information systems also provide aggregate data on immunizations for use in monitoring coverage and program operations and to guide public health action.

EVIDENCE ACQUISITION

Methods for conducting systematic reviews for the Guide to Community Preventive Services were used to assess the effectiveness of IISs. Reviewed evidence examined changes in vaccination rates in client populations or described expanded IIS capabilities related to improving vaccinations. The literature search identified 108 published articles and 132 conference abstracts describing or evaluating the use of IISs in different assessment categories.

EVIDENCE SYNTHESIS

Studies described or evaluated IIS capabilities to (1) create or support effective interventions to increase vaccination rates, such as client reminder and recall, provider assessment and feedback, and provider reminders; (2) determine client vaccination status to inform decisions by clinicians, health care systems, and schools; (3) guide public health responses to outbreaks of vaccine-preventable disease; (4) inform assessments of vaccination coverage, missed vaccination opportunities, invalid dose administration, and disparities; and (5) facilitate vaccine management and accountability.

CONCLUSIONS

Findings from 240 articles and abstracts demonstrate IIS capabilities and actions in increasing vaccination rates with the goal of reducing vaccine-preventable disease.

Vaccine Coverage for United States Infants at Milestone Ages: Missed Opportunities for Vaccination

We used a claims database to assess coverage for rotavirus (RV), diphtheria-tetanus-acellular pertussis, and pneumococcal conjugate vaccines among infants in the United States. Similar coverage was seen until 7 months of age, after which RV coverage lagged. Missed opportunities for vaccination at well-child visits were found to vary by age.

Vaccinating my way--use of alternative vaccination schedules in New York State

OBJECTIVE

To identify children vaccinated following an alternative vaccine schedule using immunization information system data and determine the impact of alternative schedule use on vaccine coverage.

STUDY DESIGN

Children born in New York State, outside New York City, between January 1, 2009 and August 14, 2011 were assessed for vaccination patterns consistent with use of an alternative schedule. Children who by 9 months of age had at least 3 vaccination visits recorded in the statewide mandatory immunization information system after 41 days of age were classified as either attempting to conform to the Centers for Disease Control and Prevention published recommended vaccination schedule or an alternative schedule. The number of vaccination visits and up-to-date status at age 9 months were compared between groups.

RESULTS

Of the 222 628 children studied, the proportion of children following an alternative schedule was 25%. These children were significantly less likely to be up-to-date at age 9 months (15%) compared with those conforming to the routine schedule (90%, P < .05). Children following an alternative schedule on average had about 2 extra vaccine visits compared with children following a routine schedule (P < .05).

CONCLUSIONS

Almost 1 in 4 children in this study appear to be intentionally deviating from the routine schedule. Intentional deviation leads to poor vaccination coverage leaving children vulnerable to infection and increasing the potential for vaccine-preventable disease outbreaks.

Evaluation of the frequency of immunization information system use for public health research

Immunization information systems (IIS) have been useful for consolidating immunization data and increasing coverage, and have the potential to be a valuable resource for immunization research, but the extent which IIS data are used for research purposes has not been evaluated. We reviewed studies conducted using data from federally supported state and city immunization program IIS, and categorized research type based on study objectives to evaluate patterns in the types of research conducted. Research papers using IIS data published between 1999 and July 3, 2012 were identified by searching the CDC IIS publication database and PubMed. These searches produced 304 and 884 papers, respectively, 44 of which were eligible to be included in this evaluation. The most common research category was evaluation of factors associated with vaccine coverage and vaccine coverage estimates (n = 20). This study shows that IIS may not be used to their full potential with regards to research. Further research is needed to determine barriers to using IIS data for research purposes.

Incomplete Early Childhood Immunization Series and Missing Fourth DTaP Immunizations; Missed Opportunities or Missed Visits?

The successful completion of early childhood immunizations is a proxy for overall quality of early care. Immunization statuses are usually assessed by up-to-date (UTD) rates covering combined series of different immunizations. However, series UTD rates often only bear on which single immunization is missing, rather than the success of all immunizations. In the US, most series UTD rates are limited by missing fourth DTaP-containing immunizations (diphtheria/tetanus/pertussis) due at 15 to 18 months of age. Missing 4th DTaP immunizations are associated either with a lack of visits at 15 to 18 months of age, or to visits without immunizations. Typical immunization data however cannot distinguish between these two reasons. This study compared immunization records from the Oregon ALERT IIS with medical encounter records for two-year olds in the Oregon Health Plan. Among those with 3 valid DTaPs by 9 months of age, 31.6% failed to receive a timely 4th DTaP; of those without a 4th DTaP, 42.1% did not have any provider visits from 15 through 18 months of age, while 57.9% had at least one provider visit. Those with a 4th DTaP averaged 2.45 encounters, while those with encounters but without 4th DTaPs averaged 2.23 encounters.

A brief review of vaccination coverage in immunization registries

Immunization registries are effective electronic tools for assessing vaccination coverage, but are only as good as the information reported to them. This review summarizes studies through August 2010 on vaccination coverage in registries and identifies key characteristics of successful registries. Based on the current state of registries, paper-based charts combined with electronic registry reporting provide the most cohesive picture of coverage. To ultimately supplant paper charts, registries must exhibit increased coverage and participation.