Measure Vaccination Coverage Research Articles

Measuring vaccination coverage and concerns of vaccine holdouts from web search logs

To design effective vaccine policies, policymakers need detailed data about who has been vaccinated, who is holding out, and why. However, existing data in the US are insufficient: reported vaccination rates are often delayed or not granular enough, and surveys of vaccine hesitancy are limited by high-level questions and self-report biases. Here we show how search engine logs and machine learning can help to fill these gaps, using anonymized Bing data from February to August 2021. First, we develop a vaccine intent classifier that accurately detects when a user is seeking the COVID-19 vaccine on Bing. Our classifier demonstrates strong agreement with CDC vaccination rates, while preceding CDC reporting by 1–2 weeks, and estimates more granular ZIP-level rates, revealing local heterogeneity in vaccine seeking. To study vaccine hesitancy, we use our classifier to identify two groups, vaccine early adopters and vaccine holdouts. We find that holdouts, compared to early adopters matched on covariates, are 67% likelier to click on untrusted news sites, and are much more concerned about vaccine requirements, development, and vaccine myths. Even within holdouts, clusters emerge with different concerns and openness to the vaccine. Finally, we explore the temporal dynamics of vaccine concerns and vaccine seeking, and find that key indicators predict when individuals convert from holding out to seeking the vaccine.

Improved vaccine coverage for First Nations children receiving first dose on-reserve: a retrospective cohort study in western Canada

IntroductionFragmentation in immunisation reporting systems pose challenges in measuring vaccine coverage for First Nations children in Canada. Some Nations have entered into data-sharing agreements with the province of Alberta’s health...

92 Trends in COVID-19 Vaccination Coverage among Children <5 Years of Age in Canada

Abstract Introduction/Background COVID-19 vaccinations for those aged 6 months to 5 years were announced in the summer of 2022. Specifically, Moderna Spikevax and Pfizer-BioNTech Comirnaty were authorized on July 14, 2022, and September 9, 2022, respectively. Given that this was the last age group to become eligible for vaccination against COVID-19, promoting and measuring vaccination coverage in this vulnerable population is of public health significance. Objectives This analysis describes and compares the trend in vaccination coverage (VC) over the initial weeks of eligibility in those 0-17 years old. Design/Methods Data were obtained from the Canadian COVID-19 Vaccination Coverage Surveillance System and were analyzed to describe and compare VC of those <5, 5-11, and 12-17-year-olds over the first 16 weeks of eligibility. VC is defined as the percent of the population that have received at least 1 dose of a COVID-19 vaccine. Results Sixteen weeks after those <5 years became eligible for vaccination, coverage was 10.9% in those aged 2-4 and 6.3% in those aged <2. Compared to other paediatric age groups, VC in those <5 is markedly lower, where, after 16 weeks of eligibility, coverage in those aged 5–11 was 54.4% and 81.5% in those 12-17. There was an immediate spike in coverage for both 5–11-year-olds and 12–17-year-olds over the first 4 weeks following eligibility, where VC was 40.1% and 63.3%, respectively. A similar increase was not observed 4 weeks following eligibility in those aged <5, where VC was 7.4% in those aged 2-4 and 4.0% in those <2. The weekly increase in VC decreased more rapidly as age groups decreased; weekly increase in VC slowed to less than 1% in 28 weeks, 20 weeks, and 16 weeks after eligibility in those aged 12-17, 5-11, and <5, respectively. Conclusion These data suggest that VC over time in the <5 population has been slow and has not followed the trajectory of other paediatric populations, when compared to the 5-11 and 12-17 age groups. Reasons for this may include but are not limited to parents and guardians’ knowledge, attitudes, and beliefs toward getting their infant children vaccinated, as well as pandemic fatigue, as eligibility for the infant population occurred after the other paediatric age groups.

Halting vaccine-derived poliovirus circulation: the novel type 2 oral vaccine might not be enough

Halting vaccine-derived poliovirus circulation: the novel type 2 oral vaccine might not be enough

Analysis of a Sabin-Strain Inactivated Poliovirus Vaccine Response to a Circulating Type 2 Vaccine-Derived Poliovirus Event in Sichuan Province, China 2019-2021

The Sabin-strain inactivated poliovirus vaccine (IPV) may be a tool for polio outbreak response in certain situations. To investigate the response to a type 2 vaccine-derived poliovirus (VDPV2) outbreak. This case series was conducted in China after a VDPV2 was detected in stool specimens from a child with acute flaccid paralysis (AFP) in Sichuan Province in 2019, 3 years after the global withdrawal of live, attenuated type 2 oral poliovirus vaccine (OPV). Investigation followed National Health Commission and World Health Organization guidance and included searching hospitals for unreported AFP cases; testing stool specimens from the child, his contacts, and local children; enhanced environmental surveillance for VDPV2s in wastewater; and measuring vaccination coverage. Sabin-strain IPV campaigns were conducted in a wide geographic area. Any VDPV2 detection after completion of the supplementary immunization activities. A 28-nucleotide-change VDPV2 was isolated from a young boy. Three VDPV2s were detected in healthy children; 2 were contacts of the original child, and none had paralysis. A search of 31 million hospital records found 10 unreported AFP cases; none were polio. No type 2 polioviruses were found in wastewater. Prior to the event, polio vaccine coverage was 65% among children younger than 5 years. Sabin-strain IPV campaigns reached more than 97% of targeted children, administering 1.4 million doses. No transmission source was identified. More than 1 year of enhanced poliovirus environmental and AFP surveillance detected no additional VDPVs. These findings suggest that the circulating VPDV2 outbreak in 2019 was associated with low vaccine coverage. An investigation discovered 3 infected but otherwise healthy children and no evidence of the virus in wastewater. Following Sabin-strain IPV-only campaigns expanding from county to prefecture, the poliovirus was not detected, and the outbreak response was considered by an expert panel and the World Health Organization to have been successful. This success suggests that the Sabin-strain IPV may be a useful tool for responding to circulating VDPV2 outbreaks when high-quality supplementary immunization activities can be conducted and carefully monitored in settings with good sanitation.

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.

Interplay between COVID-19 vaccines and social measures for ending the SARS-CoV-2 pandemic

Background: The development and authorization of COVID-19 vaccines has provided the clearest path forward to eliminate community spread and thus end the ongoing SARS-CoV-2 pandemic. However, the limited pace at which the vaccine can be administered motivates the question, to what extent must we continue to adhere to social intervention measures such as mask wearing and social distancing? Methods: We develop a mathematical model of COVID-19 spread incorporating both vaccine dynamics and socio-epidemiological parameters. We use this model to study two important measures of disease control and eradication, the effective reproductive number Rt and the peak intensive care unit (ICU) caseload, over three key parameters: social measure adherence, vaccination rate, and vaccination coverage. Results: Our results suggest that, due to the slow pace of vaccine administration, social measures must be maintained by a large proportion of the population until a sufficient proportion of the population becomes vaccinated for the pandemic to be eradicated. By contrast, with reduced adherence to social measures, hospital ICU cases will greatly exceed capacity, resulting in increased avoidable loss of life. We then investigate the threat of localized outbreaks in low-vaccinated populations that have removed all social intervention mandates, and show that such populations could remain highly susceptible to major outbreaks particularly in the face of more easily transmissible variants. Conclusions: These findings highlight the complex interplay involved between vaccination and social protective measures, and indicate the practical importance of continuing with extant social measures while vaccines are scaled up to allow the development of the herd immunity needed to end or control SARS-CoV-2 sustainably.

Added Value of Electronic Immunization Registries in Low- and Middle-Income Countries: Observational Case Study in Tanzania

BackgroundThere is growing interest and investment in electronic immunization registries (EIRs) in low- and middle-income countries. EIRs provide ready access to patient- and aggregate-level service delivery data that can be used to improve patient care, identify spatiotemporal trends in vaccination coverage and dropout, inform resource allocation and program operations, and target quality improvement measures. The Government of Tanzania introduced the Tanzania Immunization Registry (TImR) in 2017, and the system has since been rolled out in 3736 facilities in 15 regions.ObjectiveThe aims of this study are to conceptualize the additional ways in which EIRs can add value to immunization programs (beyond measuring vaccine coverage) and assess the potential value-add using EIR data from Tanzania as a case study.MethodsThis study comprised 2 sequential phases. First, a comprehensive list of ways EIRs can potentially add value to immunization programs was developed through stakeholder interviews. Second, the added value was evaluated using descriptive and regression analyses of TImR data for a prioritized subset of program needs.ResultsThe analysis areas prioritized through stakeholder interviews were population movement, missed opportunities for vaccination (MOVs), continuum of care, and continuous quality improvement. The included TImR data comprised 958,870 visits for 559,542 patients from 2359 health facilities. Our analyses revealed that few patients sought care outside their assigned facility (44,733/810,568, 5.52% of applicable visits); however, this varied by region; facility urbanicity, type, ownership, patient volume, and duration of TImR system use; density of facilities in the immediate area; and patient age. Analyses further showed that MOVs were highest among children aged <12 months (215,576/831,018, 25.94% of visits included an MOV and were applicable visits); however, there were few significant differences based on other individual or facility characteristics. Nearly half (133,337/294,464, 45.28%) of the children aged 12 to 35 months were fully vaccinated or had received all doses except measles-containing vaccine–1 of the 14-dose under-12-month schedule (ie, through measles-containing vaccine–1), and facility and patient characteristics associated with dropout varied by vaccine. The continuous quality improvement analysis showed that most quality issues (eg, MOVs) were concentrated in <10% of facilities, indicating the potential for EIRs to target quality improvement efforts.ConclusionsEIRs have the potential to add value to immunization stakeholders at all levels of the health system. Individual-level electronic data can enable new analyses to understand service delivery or care-seeking patterns, potential risk factors for underimmunization, and where challenges occur. However, to achieve this potential, country programs need to leverage and strengthen the capacity to collect, analyze, interpret, and act on the data. As EIRs are introduced and scaled in low- and middle-income countries, implementers and researchers should continue to share real-world examples and build an evidence base for how EIRs can add value to immunization programs, particularly for innovative uses.

Interplay between COVID-19 vaccines and social measures for ending the SARS-CoV-2 pandemic

Background: The development and authorization of COVID-19 vaccines has provided the clearest path forward to eliminate community spread and thus end the ongoing SARS-CoV-2 pandemic. However, the limited pace at which the vaccine can be administered motivates the question, to what extent must we continue to adhere to social intervention measures such as mask wearing and social distancing? Methods: We develop a mathematical model of COVID-19 spread incorporating both vaccine dynamics and socio-epidemiological parameters. We use this model to study two important measures of disease control and eradication, the effective reproductive number Rt and the peak intensive care unit (ICU) caseload, over three key parameters: social measure adherence, vaccination rate, and vaccination coverage. Results: Our results suggest that, due to the slow pace of vaccine administration, social measures must be maintained by a large proportion of the population until a sufficient proportion of the population becomes vaccinated for the pandemic to be eradicated. By contrast, with reduced adherence to social measures, hospital ICU cases will greatly exceed capacity, resulting in increased avoidable loss of life. We then investigate the threat of localized outbreaks in low-vaccinated populations that have removed all social intervention mandates, and show that such populations could remain highly susceptible to major outbreaks particularly in the face of more easily transmissible variants. Conclusions: These findings highlight the complex interplay involved between vaccination and social protective measures, and indicate the practical importance of continuing with extant social measures while vaccines are scaled up to allow the development of the herd immunity needed to end or control SARS-CoV-2 sustainably.

Influenza Vaccination in Patients With Congenital Heart Disease in the Pre-COVID-19 Era: Coverage Rate, Patient Characteristics, and Outcomes

BackgroundInfluenza vaccination is the most commonly recommended immune prevention strategy. However, data on influenza vaccination in patients with congenital heart disease (CHD) are scarce. In this study, our goals were to: (1) measure vaccination coverage rates (VCRs) for influenza in a large cohort of children, adolescents, and adults with CHD; (2) identify patient characteristics as predictors for vaccination; and (3) investigate the effect of influenza vaccination on hospitalization. MethodsA nationwide cohort study in Belgium included 16,778 patients, representing 134,782 vaccination years, from the Belgian Congenital Heart Disease Database Combining Administrative and Clinical Data (BELCODAC). Data over 9 vaccination years (2006-2015) were used, and patients were stratified into 5 age cohorts: 6 months to 4 years; 5-17 years; 18-49 years; 50-64 years; and 65 years and older. ResultsIn the respective age cohorts, the VCR was estimated to be 6.6%, 8.0%, 23.9%, 46.6%, and 72.8%. There was a steep increase in VCRs as of the age of 40 years. Multivariable logistic regression showed that higher anatomical complexity of CHD, older age, presence of genetic syndromes, and previous cardiac interventions were associated with significantly higher VCRs. Among adults, men had lower and pregnant women had higher VCRs. The association between influenza vaccination and all-cause hospitalization was not significant in this study. ConclusionsThe influenza VCR in people with CHD is low, especially in children and adolescents. Older patients, particularly those with complex CHD, are well covered. Our findings should inform vaccination promotion strategies in populations with CHD.

Pairs of independent nationally representative vaccination coverage surveys conducted within one year of each other: A global overview covering 2000–2019

BackgroundPopulation-based surveys play an important role in measuring vaccination coverage. Surveys measuring vaccination coverage may be commissioned by the Expanded Programme on Immunization (EPI surveys) or part of multi-domain non-EPI surveys such as Demographic and Health Surveys (DHS) or Multiple Indicator Cluster Surveys (MICS). Surveys conducted too close in time to each other may not only be an inefficient use of resources but may also create problems for programme staff when results suggest inconsistent patterns of programme performance for similar time periods. ObjectiveTo summarize the occurrence of vaccination coverage surveys conducted close in time during 2000–2019 and compare results of EPI and non-EPI coverage surveys when the surveys were conducted within one year of each other. MethodsUsing a database of published national-level vaccination coverage survey results compiled by the World Health Organization (WHO) and the United Nations Children’s Fund (UNICEF), the authors abstracted information on survey field work dates, sample size, percentage of children with documented history of vaccination and the percent coverage, as well as published uncertainty intervals from DHS and MICS, for the first and third doses of diphtheria-tetanus toxoid-pertussis containing vaccine (DTP1, DTP3) and first dose of measles containing vaccine (MCV1). Survey results of EPI and non-EPI surveys were compared. ResultsThe authors identified 646 surveys with final reports and estimates of national-level vaccination coverage for DTP1, DTP3, or MCV1 from a total of 687 surveys with data collection start date from 2000 to 2019. Of the 140 countries with at least one vaccination coverage survey, a median of four surveys was observed. Most countries were Gavi-eligible and located in the WHO Africa Region. Sixty-six survey dyads were identified where an EPI survey occurred within one year of a non-EPI survey. For the 66 dyads, in 49 of 59 with information available, EPI surveys reported higher proportion of documented evidence of vaccination and EPI survey results tended to suggest higher levels of vaccination coverage compared to the non-EPI surveys; quite often, differences were substantial. Surveys that found higher proportions of children with documented vaccination evidence tended to also find higher proportions of children who had been vaccinated. SummaryOpportunities exist to improve overall planning of vaccination coverage measurement in population-based household surveys so that both EPI and non-EPI surveys are more comparable and survey coverage estimates are more appropriately spaced in time. When surveys occur too close in time, careful attention is warranted to ensure comparability and assess sources of documented evidence of vaccination and related coverage differences.

Effectiveness and Equity of Australian Vaccine Mandates.

* Abbreviations: NJNPlay — : No Jab No Play NJNPay — : No Jab No Pay In this issue of Pediatrics , Attwell et al1 assess the impact of two policy changes on childhood vaccination coverage in Australia. Conducting an interrupted time series analysis, the authors measure vaccination coverage of Australian children at 12 and 60 months at federal, state, and community levels after the implementation of (1) “No Jab, No Play” (NJNPlay), state-level policies denying unvaccinated children enrollment in preschool starting in 2014; and (2) “No Jab, No Pay” (NJNPay), a federal-level policy linking vaccination receipt to government family assistance payments enacted in 2016. This study is an important contribution to the vaccination policy literature and an intriguing study of behavioral theory and health equity. Psychology is an essential part of vaccine intervention design. In an exhaustive review, Brewer et al2 summarized the vaccination and psychology literature in 2017, finding 3 ways researchers have leveraged psychology to increase vaccination: (1) understanding and changing thoughts and feelings about infectious diseases and vaccines via direct communication, (2) leveraging social processes and norms to alter vaccination behaviors, and (3) facilitating direct behavior change … Address correspondence to Joshua T. B. Williams, MD, Denver Health Medical Center, 301 W 6th Ave, MC #1911, Denver, CO 80204. E-mail: joshua.williams{at}dhha.org

Complete human papillomavirus vaccination coverage over a 13-year period in a large population of privately insured U.S. patients.

1511 Background: In the US, Human Papillomavirus (HPV) vaccination coverage is low, particularly in adolescents aged 13-15 years with respect to the Healthy People 2020 goal of 80%. There has been variability in the definition of measuring vaccination coverage in published studies. We examined complete HPV vaccination coverage in a population of privately insured individuals in the US. Methods: This retrospective study used IBM MarketScan Commercial Database, years 2006 to 2018. Inclusion criteria were ages 9 to 45 years and continuous enrollment from age 9 years or from 2006. Complete HPV vaccination coverage was defined as receipt of 2 doses (age 9-15 years) or 3 doses (age 16-45 years) within 12 months and stratified by year, demographics, and US region. Mean vaccination costs per dose were summarized by vaccine brand and health plan type. Results: The table summarizes complete HPV vaccination coverage by selected age groups for 2006 (n=12,221,938), 2010 (n=4,692,633), 2014 (n=2,808,132), and 2018 (n=1,662,148). From 2017 to 2018, the percentage of members who received HPV vaccine increased; for females ages 13-15 by 1% and 16-17 by 5% while for males ages 13-15 by 6% and 16-17 by 15%. In 2018, by region, the highest coverage was in females aged 18-26 at 53% and males aged 16-17 at 43% in the Northeast, and mean cost for each brand was $120 (-6% from 2017), $165 (-3%) and $220 (+5%) for Cervarix (n=151), Gardasil (n=8,201) and Gardasil 9 (n=139,356), respectively. The rate of utilization of Gardasil 9 increased from 33% (2015) to 94% (2018) of all vaccines. The lowest mean HPV vaccine cost by health plan type and brand was with Point-of-Service (POS) and Cervarix at $106, and the highest was with POS with Capitation and Gardasil 9 at $243. Conclusions: In a commercially insured US population, complete HPV vaccination coverage was lower than the Healthy People 2020 goal, but increased over time. Coverage varied according to health plan type and by region. In 2018, Gardasil 9 had the highest mean cost but was the most utilized vaccine, which may be related to broader coverage of HPV types. This study was limited by the transient nature of member enrollment and complexity of measuring complete vaccination coverage. These results should inform policy makers and practicing clinicians about the gap in vaccination coverage. [Table: see text]

Assessment of vaccination coverage of adolescents aged 16–18 years with an innovative electronic immunization record system

ObjectivesTo measure vaccine coverage among adolescents aged 16–18 years who participated in the National Defense Preparation Day in the Aquitaine region using the free electronic immunization record. Patients and methodsWe considered adolescents aged 16–18 years who participated in the National Defense Preparation Day in the Aquitaine region from April to October 2013. All participants received a letter explaining how to create an electronic immunization record. Those records were then validated by checking data against the copies of the vaccination cards brought by participants on the day they attended. Vaccination coverage was estimated for eight vaccinations according to the cumulative number of doses registered and vaccines recommended during childhood. ResultsAmong the 18,714 participants, 9636 agreed to create an electronic immunization record of which 2781 were validated. Vaccination coverage was˃90% for tuberculosis, diphtheria-tetanus-poliomyelitis, measles-mumps-rubella, and Haemophilus influenzae type B, and˂90% for pertussis, hepatitis B, meningococcal C disease, and human papillomavirus. These coverage rates were close to those reported in other available sources. ConclusionOur study calls attention to the insufficient vaccination of adolescents for pertussis, HBV, meningococcal C disease, and HPV. The absence of a system that routinely provides the vaccination status of this population is a major public health issue in France. The use of an electronic immunization record was innovative, but this tool is not extensively used in the general population and has been evaluated by Santé publique France (the French national public health agency).

Predictors of seasonal influenza vaccination among older adults in Thailand.

BackgroundIn advance of a large influenza vaccine effectiveness (VE) cohort study among older adults in Thailand, we conducted a population-based, cross-sectional survey to measure vaccine coverage and identify factors associated with influenza vaccination among older Thai adults that could bias measures of vaccine effectiveness.MethodWe selected adults ≥65 years using a two-stage, stratified, cluster sampling design. Functional status was assessed using the 10-point Vulnerable Elders Survey (VES); scores ≥3 indicated vulnerability. Questions about attitudes towards vaccination were based on the Health Belief Model. The distance between participants’ households and the nearest vaccination clinic was calculated. Vaccination status was determined using national influenza vaccination registry. Prevalence ratios (PR) and 95% confidence intervals (CIs) were calculated using log-binomial multivariable models accounting for the sampling design.ResultWe enrolled 581 participants, of whom 60% were female, median age was 72 years, 41% had at least one chronic underlying illness, 24% met the criteria for vulnerable, and 23% did not leave the house on a daily basis. Influenza vaccination rate was 34%. In multivariable models, no variable related to functional status was associated with vaccination. The strongest predictors of vaccination were distance to the nearest vaccination center (PR 3.0, 95% CI 1.7–5.1 for participants in the closest quartile compared to the furthest), and high levels of a perception of benefits of influenza vaccination (PR 2.8, 95% CI 1.4–5.6) and cues to action (PR 2.7, 95% CI 1.5–5.1).ConclusionDistance to vaccination clinics should be considered in analyses of influenza VE studies in Thailand. Strategies that emphasize benefits of vaccination and encourage physicians to recommend annual influenza vaccination could improve influenza vaccine uptake among older Thai adults. Outreach to more distant and less mobile older adults may also be required to improve influenza vaccination coverage.

Challenges in Estimating Vaccine Coverage in Refugee and Displaced Populations: Results From Household Surveys in Jordan and Lebanon.

Ensuring the sustained immunization of displaced persons is a key objective in humanitarian emergencies. Typically, humanitarian actors measure coverage of single vaccines following an immunization campaign; few measure routine coverage of all vaccines. We undertook household surveys of Syrian refugees in Jordan and Lebanon, outside of camps, using a mix of random and respondent-driven sampling, to measure coverage of all vaccinations included in the host country’s vaccine schedule. We analyzed the results with a critical eye to data limitations and implications for similar studies. Among households with a child aged 12–23 months, 55.1% of respondents in Jordan and 46.6% in Lebanon were able to produce the child’s EPI card. Only 24.5% of Syrian refugee children in Jordan and 12.5% in Lebanon were fully immunized through routine vaccination services (having received from non-campaign sources: measles, polio 1–3, and DPT 1–3 in Jordan and Lebanon, and BCG in Jordan). Respondents in Jordan (33.5%) and Lebanon (40.1%) reported difficulties obtaining child vaccinations. Our estimated immunization rates were lower than expected and raise serious concerns about gaps in vaccine coverage among Syrian refugees. Although our estimates likely under-represent true coverage, given the additional benefit of campaigns (not captured in our surveys), there is a clear need to increase awareness, accessibility, and uptake of immunization services. Current methods to measure vaccine coverage in refugee and displaced populations have limitations. To better understand health needs in such groups, we need research on: validity of recall methods, links between campaigns and routine immunization programs, and improved sampling of hard-to-reach populations.

Measuring vaccination coverage better will help achieve disease control.

Timely and accurate measurement of vaccination coverage is required to evaluate the success of vaccine programmes as well as identifying susceptible groups in order to better control disease. Estimating coverage requires knowledge of how many people are eligible for vaccination, and how many have received the vaccine. Achieving this presents a number of challenges in both high and low income settings. Investing in systems that record vaccination coverage better, as an integral part of vaccine strategies, will be a step towards better control of vaccine-preventable diseases.

Vaccination coverage and immunization timeliness among children aged 12-23 months in Senegal: a Kaplan-Meier and Cox regression analysis approach.

IntroductionExpanded programme on immunizations in resource-limited settings currently measure vaccination coverage defined as the proportion of children aged 12-23 months that have completed their vaccination. However, this indicator does not address the important question of when the scheduled vaccines were administered. We assessed the determinants of timely immunization to help the national EPI program manage vaccine-preventable diseases and impact positively on child survival in Senegal.MethodsVaccination data were obtained from the Demographic and Health Survey (DHS) carried out across the 14 regions in the country. Children were aged between 12-23 months. The assessment of vaccination coverage was done with the health card and/or by the mother’s recall of the vaccination act. For each vaccine, an assessment of delay in age-appropriate vaccination was done following WHO recommendations. Additionally, Kaplan-Meier survival function was used to estimate the proportion vaccinated by age and cox-proportional hazards models were used to examine risk factors for delays.ResultsA total of 2444 living children between 12–23 months of age were included in the analysis. The country vaccination was below the WHO recommended coverage level and, there was a gap in timeliness of children immunization. While BCG vaccine uptake was over 95%, coverage decreased with increasing number of Pentavalent vaccine doses (Penta 1: 95.6%, Penta 2: 93.5%: Penta 3: 89.2%). Median delay for BCG was 1.7 weeks. For polio at birth, the median delay was 5 days; all other vaccine doses had median delays of 2-4 weeks. For Penta 1 and Penta 3, 23.5% and 15.7% were given late respectively. A quarter of measles vaccines were not administered or were scheduled after the recommended age. Vaccinations that were not administered within the recommended age ranges were associated with mothers’ poor education level, multiple siblings, low socio-economic status and living in rural areas.ConclusionA significant delay in receipt of infant vaccines is found in Senegal while vaccine coverage is suboptimal. The national expanded program on immunization should consider measuring age at immunization or using seroepidemiological data to better monitor its impact.

Pertussis vaccination coverage among French parents of infants after 10 years of cocoon strategy

ObjectivesThe cocoon strategy against pertussis has been recommended in France since 2004 to indirectly protect young infants who are not yet vaccinated. We aimed to measure vaccination coverage among French parents of infants. MethodsA representative sample of 300 mothers and 200 fathers of infants aged <12 months completed a self-administered online questionnaire. They all provided their own vaccination records. ResultsOverall, 87% of mothers believed vaccination against pertussis to be important; 83% reported being immunized against pertussis but their vaccination records showed that a third of them was wrong (34%). On the basis of our sample, the 2009–2014 vaccination coverage against pertussis among mothers increased from 22 to 61% (P<0.005); over the same period of time, vaccination coverage against diphtheria, tetanus, and polio remained stable (80%). Vaccination coverage against pertussis among fathers increased from 21 to 42% between 2010 and 2013 (P=0.009). In 2013, one couple out of four (26%) was adequately immunized against pertussis. ConclusionThe cocoon strategy was implemented 10years ago in France but vaccination coverage remains suboptimal among parents of young infants. Healthcare professionals must recommend vaccination against pertussis to young adults and check that their vaccination status is up to date.

Validation of infant immunization billing codes in administrative data

Ontario has a single payer provincial health insurance program. Administrative data may provide a potentially robust source of information for post-marketing vaccine studies. Vaccine-specific immunization billing codes were introduced in 2011. Our objective was to validate Ontario's universal health care administrative datasets to assess infant immunization status. Electronic medical record data from the Electronic Medical Record Administrative data Linked Database (EMRALD) was used as the reference standard to calculate performance characteristics of the Ontario Health Insurance Plan (OHIP) database vaccine-specific and general immunization codes for 4 primary infant immunizations: diphtheria, tetanus, acellular pertussis, inactivated polio, Haemophilus influenzae type B (DTaP-IPV-Hib) combination vaccine, pneumococcal conjugate vaccine, measles, mumps, rubella (MMR) vaccine, and meningococcal conjugate serogroup C vaccine. OHIP billing claims had specificity ranging from 81% to 92%, sensitivity 70% to 83%, positive predictive value (PPV) 97% to 99%, and negative predictive value (NPV) 13% to 46% for identifying the various specific vaccines in administrative data. For cohorts vaccinated in the new code introduction phase, using both the vaccine-specific and general codes had higher sensitivity than the vaccine-specific codes alone. In conclusion, immunization billing claims from administrative data in Ontario had high specificity and PPV, moderate sensitivity, and low NPV. This study identifies some of the applications of utilizing administrative data for post-marketing vaccine studies. However, limitations of these data decrease their utility for measuring vaccine coverage and effectiveness. Therefore, the establishment of a comprehensive and linkable immunization registry should be a provincial priority.