Missed opportunities for simultaneous administration of the fourth dose of DTaP among children in the United States

Completion of multidose vaccine series in early childhood: current challenges and opportunities

PURPOSE OF REVIEW

Completion of all doses in multidose vaccine series provides optimal protection against preventable infectious diseases. In this review, we describe clinical and public health implications of multidose vaccine series noncompletion, including current challenges to ensuring children receive all recommended vaccinations. We then highlight actionable steps toward achieving early childhood immunization goals.

RECENT FINDINGS

Although coverage levels are high for most early childhood vaccinations, rates of completion are lower for vaccinations that require multiple doses. Recent research has shown that lower family socioeconomic status, a lack of health insurance coverage, having multiple children in the household, and moving across state lines are associated with children failing to complete multidose vaccine series. These findings provide contextual evidence to support that practical challenges to accessing immunization services are impediments to completion of multidose series. Strategies, including reminder/recall, use of centralized immunization information systems, and clinician prompts, have been shown to increase immunization rates. Re-investing in these effective interventions and modernizing the public health infrastructure can facilitate multidose vaccine series completion.

SUMMARY

Completion of multidose vaccine series is a challenge for immunization service delivery. Increased efforts are needed to address remaining barriers and improve vaccination coverage in the United States.

Missed opportunities for vaccination at point of care and their impact on coverage and urban-rural coverage inequity in the Gambia

INTRODUCTION

Identifying actionable targets is crucial to improve overall and equity in vaccination coverage, and in line with the global Immunization Agenda 2030. Therefore, this study seeks to assess the prevalence of missed opportunities for simultaneous vaccination (MOSVs) and their impact on vaccination coverage and urban-rural inequity in The Gambia.

METHODS

We used data of children aged 12-23 months from The Gambia 2019/2020 demographic and health survey (weighted n = 1355) with seen vaccination cards. We analyzed: the frequency of MOSVs; percentage point coverage reduction attributable to MOSVs for 18 vaccine doses and full basic vaccination; and MOSVs' contribution to urban-rural coverage inequity through Blinder-Oaxaca decomposition.

RESULTS

Sixty percent of children experienced MOSVs, in both urban and rural areas, but urban MOSVs were more seldom corrected (35.9 % vs 45.3 %). All eighteen vaccine doses assessed could have achieved between one to eleven percentage points higher coverage if MOSVs had been avoided, with full basic vaccination gaining even more. While MOSV correction did not impact overall urban-rural coverage inequity, it did exacerbate (explained coefficient = -0.1007; P = 0.002) inequities among children who experienced MOSVs, explaining 95 % of the observed difference.

CONCLUSION

Our study highlights the prevalence and negative impact of MOSVs on overall vaccination coverage. Although MOSVs did not contribute significantly to the total urban-rural inequity in coverage, they have detrimental effects on vaccination coverage and urban-rural inequity among children who had experienced MOSVs. Addressing MOSVs, can enhance coverage and reduce the risk of under-vaccination, aligning with global initiatives.

Factors Contributing to the Delayed Vaccination Among Children in Riyadh City, Saudi Arabia: A Cross-Sectional Study

Background Immunizations protect children from deadly infectious diseases. The timeliness of vaccinating children is crucial to ensure effective immunization and to decrease the burden of many infectious diseases. Therefore, this study assessed the prevalence and determinants of vaccination delay among children in Riyadh City, Saudi Arabia. Methods This cross-sectional study was conducted at the primary healthcare centers in Riyadh City, Saudi Arabia, on 593 parents with children of two years of age or below. It used a self-administered questionnaire inquiring about socio-demographic characteristics and assessing the vaccination statuses of their children and the causes of delayed vaccinations. Results The results showed that 7.1% of children had a delay in the previous vaccination. Of those delays, collectively, 77.5% were delays in inactivated poliovirus vaccine (IPV), oral poliovirus vaccine (OPV), and meningococcal vaccine (MCV) vaccines. The delay was mostly caused by an illness of the child on vaccination day, carelessness of parents, or long postponement. After adjusting for confounders, the father's high school or bachelor's education level (OR = 1.18, 95% CI: 1.03, 1.36) (p<0.05), child's mix-type nutrition (OR = 1.06, 95% CI: 1.02, 1.10) (p=0.001), and the belief that multiple vaccines are harmful to the child (POR = 1.03, 95% CI: 1.01, 1.06) (p=0.005) were positively associated with vaccination delay, while prematurity was negatively associated with vaccination delay (OR = 0.96, 95% CI: 0.93, 0.99) (p=0.031). Conclusion The study found the prevalence of vaccination delay was lower than in previous COVID-19-era studies. The child's illness was the main reason for the delay. Factors like parental education, nutrition type, and vaccine beliefs contributed to delays, while prematurity reduced delays. Measures should be strengthened to increase vaccination coverage for children.

Failure to Complete Multidose Vaccine Series in Early Childhood

BACKGROUND

Most early childhood immunizations require 3 to 4 doses to achieve optimal protection. Our objective was to identify factors associated with starting but not completing multidose vaccine series.

METHODS

Using 2019 National Immunization Survey-Child data, US children ages 19 to 35 months were classified in 1 of 3 vaccination patterns: (1) completed the combined 7-vaccine series, (2) did not initiate ≥1 of the 7 vaccine series, or (3) initiated all series, but did not complete ≥1 multidose series. Associations between sociodemographic factors and vaccination pattern were evaluated using multivariable log-linked binomial regression. Analyses accounted for the survey's stratified design and complex weighting.

RESULTS

Among 16 365 children, 72.9% completed the combined 7-vaccine series, 9.9% did not initiate ≥1 series, and 17.2% initiated, but did not complete ≥1 multidose series. Approximately 8.4% of children needed only 1 additional vaccine dose from 1 of the 5 multidose series to complete the combined 7-vaccine series. The strongest associations with starting but not completing multidose vaccine series were moving across state lines (adjusted prevalence ratio [aPR] = 1.45, 95% confidence interval [CI]: 1.18-1.79), number of children in the household (2 to 3: aPR = 1.29, 95% CI: 1.05-1.58; 4 or more: aPR = 1.68, 95% CI: 1.30-2.18), and lack of insurance coverage (aPR = 2.03, 95% CI: 1.42-2.91).

CONCLUSIONS

More than 1 in 6 US children initiated but did not complete all doses in multidose vaccine series, suggesting children experienced structural barriers to vaccination. Increased focus on strategies to encourage multidose series completion is needed to optimize protection from preventable diseases and achieve vaccination coverage goals.

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.

Evaluating vaccination coverage and timeliness in American Indian/Alaska Native and non-Hispanic White children using state immunization information system data, 2015-2017

Comprehensive estimates of vaccination coverage and timeliness of vaccine receipt among American Indian/Alaska Native (AI/AN) children in the United States are lacking. This study’s objectives were to quantify vaccination coverage and timeliness, as well as the proportion of children with specific undervaccination patterns, among AI/AN and non-Hispanic White (NHW) children ages 0–24 months in Montana, a large and primarily rural U.S. state. Data from Montana’s immunization information system (IIS) for children born 2015–2017 were used to calculate days undervaccinated for all doses of seven recommended vaccine series. After stratifying by race/ethnicity, up-to-date coverage at key milestone ages and the proportion of children demonstrating specific patterns of undervaccination were reported. Among n = 3,630 AI/AN children, only 23.1% received all recommended vaccine doses on-time (i.e., zero days undervaccinated), compared to 40.4% of n = 18,022 NHW children (chi-square p < 0.001). A greater proportion of AI/AN children were delayed at each milestone age, resulting in lower overall combined 7-vaccine series completion, by age 24 months (AI/AN: 56.6%, NHW: 64.3%, chi-square p < 0.001). As compared with NHW children, a higher proportion of AI/AN children had undervaccination patterns suggestive of structural barriers to accessing immunization services and delayed starts to vaccination. More than three out of four AI/AN children experienced delays in vaccination or were missing doses needed to complete recommended vaccine series. Interventions to ensure on-time initiation of vaccine series at age 2 months, as well initiatives to encourage completion of multi-dose vaccine series, are needed to reduce immunization disparities and increase vaccination coverage among AI/AN children in Montana.

Vaccine timeliness and prevalence of undervaccination patterns in children ages 0-19 months, U.S., National Immunization Survey-Child 2017

OBJECTIVES

Typically, early childhood vaccination coverage in the U.S. is measured as the proportion of children by age 24 months who completed recommended vaccine series. However, these measures do not reflect whether vaccine doses were received at the ages recommended by the U.S. Advisory Committee on Immunization Practices, or whether children received vaccines concomitantly, per the ACIP recommended schedule. This study's objective was to quantify vaccine timeliness and prevalence of specific patterns of undervaccination in U.S. children ages 0-19 months.

METHODS

Using 2017 National Immunization Survey-Child data, we calculated days undervaccinated for the combined 7-vaccine series and distinguished undervaccination patterns indicative of parental vaccine hesitancy, such as spreading out vaccines across visits ("shot-limiting") or starting some but not all recommended vaccine series ("selective vaccination"), from other non-hesitancy patterns, such as missing final vaccine doses or receiving all doses, with some or all late. We measured associations between demographic, socioeconomic and other characteristics with undervaccination patterns using multivariable log-linked binomial regression. Analyses accounted for the complex survey design.

RESULTS

Among n = 15,333 U.S. children, only 41.2% received all recommended vaccine doses on-time by age 19 months. Approximately 20.9% of children had an undervaccination pattern suggestive of parental vaccine hesitancy, and 36.2% had other undervaccination non-hesitancy patterns. Uninsured children and those with lower levels of maternal education were more likely to exhibit undervaccination patterns suggestive of parental hesitancy. Lower levels of maternal education were also associated with other non-hesitancy undervaccination patterns.

CONCLUSIONS

More than half of children in the U.S. are undervaccinated at some point by 19 months of age. Ongoing assessment of vaccine timeliness and immunization schedule adherence could facilitate timely and targeted public health interventions in populations with high levels of undervaccination.

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.

Improving childhood vaccination coverage rates: the case of fourth dose of DTaP

Based on the most recently available national data, vaccination coverage for the combined seven-vaccine series recommended by age 24 months remains substantially below the Healthy People 2020 target of 80%. One focus for improvement is the lack of timely administration of the fourth dose of DTaP vaccine. Based on the perspective of state and local immunization program managers, key strategies include tracking immunization patterns through immunization information systems and other data sources, working with health-care providers to address challenges to timely vaccination, and developing partnerships with daycares, payers, and health systems.

Neighbourhood influence on the fourth dose of diphtheria-tetanus-pertussis vaccination

OBJECTIVES

Using 542,159 vaccination records from children born between April 1, 2007, and March 31, 2012, in the Michigan Care Improvement Registry and data from the American Community Survey, we determine if neighbourhood-level characteristics at the Census tract level and block level are associated with low uptake of the fourth dose of diphtheria-tetanus-acellular pertussis vaccine (DTaP4).

STUDY DESIGN

This study was a cross-sectional study.

METHODS

We used exploratory factor analysis to determine important socio-economic factors at the Census block level and tract level. We then used generalised estimating equations to test the relationship between block- and tract-level socio-economic factors and DTaP4 uptake.

RESULTS

DTaP4 coverage was 88.6% (95% confidence interval [CI]: 88.4%-88.7%) in Michigan. At the Census tract level, two factors surfaced as important for DTaP4 vaccination: 'affluence' (Cronbach's alpha = 0.88) and 'socio-economic disadvantage' (Cronbach's alpha = 0.89). At the Census block level, one factor was important: 'affluence' (Cronbach's alpha = 0.90). Affluence may relate to knowledge about medical exemptions and antivaccination sentiment, while socio-economic disadvantage may indicate limited access to healthcare resources. Children in high-affluence tracts had 1.08% lower vaccination coverage (95% CI: -1.62% to -0.55%) than children in low affluence tracts. Children in low socio-economic disadvantage tracts had 2.92% higher coverage than children in high socio-economic disadvantage tracts (95% CI: 2.58%-3.26%).

CONCLUSIONS

This study articulates the need to further understand the contribution of neighbourhood-level characteristics, from both affluent and socioeconomically disadvantaged areas to low vaccination rates. Developing a better understanding of these social environmental factors will help determine useful community-level interventions to improve vaccination rates and reduce disease burden.

Impact of vaccine delays at the 2, 4, 6 and 12 month visits on incomplete vaccination status by 24 months of age in Quebec, Canada

BACKGROUND

Timeliness in the administration of recommended vaccines is often evaluated using vaccine delays and provides more information regarding the susceptibility of children to vaccine-preventable diseases compared with vaccine coverage at a given age. The importance of on-time administration of vaccines scheduled at the first visit is well documented, but data are scarce about the impact of vaccine delays at other visits on vaccination status by 24 months of age. Using vaccine delays for the first three doses of DTaP-containing vaccines and for the first dose of measles-containing vaccines as markers of timeliness at the 2, 4, 6 and 12 month visits, we estimated the proportion of incomplete vaccination status by 24 months of age attributable to a vaccine delay at each of these visits.

METHODS

We used the data from six cross-sectional coverage surveys conducted in the Province of Quebec from 2006 to 2016 which included 7183 children randomly selected from the universal health insurance database. A vaccine dose was considered delayed if received 30 days or more after the recommended age. The impact of new vaccine delays at each visit on incomplete vaccination status by 24 months of age was estimated with the attributable risk in the population.

RESULTS

The proportion of children with vaccine delay was 5.4% at 2 months, 13.3% at 4 months, 23.1% at 6 months and 23.6% at 12 months. Overall, 72.5% of all 2-year-old children with an incomplete status by 24 months were attributable with a vaccine delay, of which 16.1% were attributable with a first vaccine delay at 2 months, 10.6% at 4 months, 14.0% at 6 months and 31.8% at 12 months.

CONCLUSIONS

While great emphasis has been put on vaccine delays at the first vaccination visit, the prevalence of vaccine delays was greater with later visits and most children with an incomplete vaccination status by 24 months had a vaccine delay occurring during these later visits. Interventions to improve timeliness should address vaccine delays at each visit and not only focus on the first visit.

Impact of the addition of new vaccines in the early childhood schedule on vaccine coverage by 24 months of age from 2006 to 2016 in Quebec, Canada

CONTEXT

Between 2004 and 2016, in the province of Quebec (Canada), 4 new antigens were added in the early childhood vaccine schedule from birth to 18 months, increasing the number of injections or doses needed from 7 to 12. These additions may have decreased the proportion of children who had received all recommended vaccines.

OBJECTIVES

To assess the impact of the introduction of new vaccines to the childhood schedule on the 24-month vaccine coverage from 2006 to 2016 and identify factors associated with incomplete vaccination status by 24 months of age.

METHODS

We used the data from six cross-sectional vaccine coverage surveys conducted every two years which included a total of 3515 children aged 2 years old and randomly selected from the Quebec public health insurance database. Factors associated with an incomplete vaccine status by 24 months were identified with multivariable logistic regression.

RESULTS

Despite the addition of 4 new vaccine antigens since 2004, the vaccine coverage remained high from 2006 (82.4%) through 2016 (88.3%) for vaccines present in the schedule since 2006. In 2016, vaccine coverage was 78.2% for all vaccines included in the schedule. The vaccine coverage of new vaccines increases rapidly within 2 years of their introduction. For both new and older vaccines, incomplete vaccine status by 24 months of age is associated with a delay of 30 days or more in receiving the vaccines scheduled at 2 and 12 months of age.

CONCLUSIONS

Increasing to 12 the number of doses in the recommended schedule has slightly reduced the vaccine coverage by 24 months of age and the vaccine coverage of vaccines already in the schedule remained stable over the years. Future additions to the vaccine schedule may not be similarly accepted by the population and this will require continuing the monitoring of vaccine coverage.

Evaluation of potentially achievable vaccination coverage of the second dose of measles containing vaccine with simultaneous administration and risk factors for missed opportunities among children in Zhejiang province, east China

OBJECTIVES

This study aimed to evaluate the potential achievable coverage of the second dose of measles containing vaccine (MCV2) when the protocol of simultaneous administration of childhood vaccines was fully implemented. Risk factors for missed opportunity (MO) for simultaneous administration of MCV2 were also investigated.

METHODS

Children born from 1 January 2005 to 31 December 2014 and registered in Zhejiang provincial immunization information system were enrolled in this study. The MO of simultaneous administration of MCV2, the actual age-appropriate coverage (AAC) of MCV2 and the potentially achievable coverage (PAC) of MCV2 were evaluated and compared across different birth cohorts, by different socio-demographic variables. For the 2014 birth cohort, logistic regression model was used to detect the risk factors of MOs, from both socio-demographic and vaccination service providing aspects.

RESULTS

Compared to the AAC, the PAC of MCV2 increased significantly from 2005 birth cohort to 2014 birth cohort (p<0.001), with a median of 12.7 percentage points. Higher birth order of children, resident children, higher maternal education background, higher socio-economic development level of resident areas, less frequent vaccination service, and shorter vaccination service time were significant risk factors of MO for simultaneous administration of MCV2, with all p-value < 0.05.

CONCLUSION

The findings in this study suggest that fully utilization of all opportunities for simultaneous administration of all age-eligible vaccine doses at the same vaccination visit is critical for achieving the coverage target of 95% for MCV2. Future interventions focusing on the group with risk factors observed could substantially eliminate MOs for simultaneous administration of MCV2, further to improve the coverage of fully immunization of MCV, and finally achieve the goal of eliminating measles.