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Background GAVI’s focus on reducing inequities in access to vaccines, immunization, and GAVI funds, − both between and within countries - has changed over time. This paper charts that evolution. Methods A systematic qualitative review was conducted by searching PubMed, Google Scholar and direct review of available GAVI Board papers, policies, and program guidelines. Documents were included if they described or evaluated GAVI policies, strategies, or programs and discussed equity of access to vaccines, utilization of immunization services, or GAVI funds in countries currently or previously eligible for GAVI support. Findings were grouped thematically, categorized into time periods covering GAVI’s phases of operations, and assessed depending on whether the approaches mediated equity of opportunity or equity of outcomes between or within countries. Results Serches yielded 2816 documents for assessment. After pre-screening and removal of duplicates, 552 documents underwent detailed evaluation and pertinent information was extracted from 188 unique documents. As a global funding mechanism, GAVI responded rationally to a semi-fixed funding constraint by focusing on between-country equity in allocation of resources. GAVI’s predominant focus and documented successes have been in addressing between-country inequities in access to vaccines comparing lower income (GAVI-eligible) countries with higher income (ineligible) countries. GAVI has had mixed results at addressing between-country inequities in utilization of immunization services, and has only more recently put greater emphasis and resources towards addressing within-country inequities in utilization to immunization services. Over time, GAVI has progressively added vaccines to its portfolio. This expansion should have addressed inter-country, inter-regional, inter-generational and gender inequities in disease burden, however, evidence is scant with respect to final outcomes. Conclusion In its next phase of operations, the Alliance can continue to demonstrate its strength as a highly effective multi-partner enterprise, capable of learning and innovating in a world that has changed much since its inception. By building on its successes, developing more coherent and consistent approaches to address inequities between and within countries and by monitoring progress and outcomes, GAVI is well-positioned to bring the benefits of vaccination to previously unreached and underserved communities towards provision of universal health coverage.

Digital health interventions, such as electronic immunization registries (eIRs) and electronic logistic management information systems (eLMIS), have the potential to significantly improve immunization data management and vaccine logistics in low- and middle-income countries (LMICs). Despite their growing adoption, there is limited evidence of the financial and economic costs associated with their implementation compared to traditional paper-based systems. We aimed to measure the costs of implementing eIR and eLMIS systems in LMICs and to estimate their economic costs as compared to the previous paper-based registries. The study was conducted across four countries-Guinea, Honduras, Rwanda, and Tanzania-which implemented the tools in 2018, 2012, 2019, and 2014, respectively. A combination of primary and secondary data sources was used for the analysis. Retrospective cost data regarding the design, development, and implementation of the tools were directly obtained from implementers and National Immunization Program offices in all countries. Primary survey data were collected to gauge the operational expenses of immunization information systems, both with and without electronic tools, using an activity-based costing approach in 275 facilities. The annual cost of the immunization information system at the national level was then extrapolated and compared to national spending on immunization as a measure of affordability. Costs were reported in 2023 international dollars (I$). The total costs of designing, developing, and deploying eIR, eLMIS, or both were I$ 2.2, 6.4, 6.8, and 44.3 million in Guinea, Honduras, Rwanda, and Tanzania, respectively. Design costs were greatly affected by the degree of customization of the tool, whereas rollout costs were mostly driven by the costs of purchasing hardware and training health workers. Overall, the implementation of the electronic systems was associated with higher costs in Honduras (I$626 per facility, 95% CI 516-821) and Rwanda (I$399, 95% CI I$108-I$691), a cost reduction in Tanzania (-I$2539, 95% CI -I$4290 to -I$789) and no significant cost difference in Guinea. The percentage weight of the cost of managing data with the electronic systems over the total national immunization budgets was estimated at 0.7%, 7.7%, 3.3%, and 4.8% for Guinea, Honduras, Rwanda, and Tanzania, respectively. Digital health interventions such as eIR and eLMIS can potentially reduce costs and improve the efficiency of immunization data management and vaccine logistics in LMICs. However, the extent of cost savings depends on how effectively these digital systems replace traditional paper-based methods and the extent of their use in decision-making, especially at the facility level. Careful planning and investment are essential to unlocking the full economic potential of digital health in LMICs.

Background Completion of multiple dose vaccine schedules is crucial to ensure a protective immune response, and maximise vaccine cost-effectiveness. While barriers and facilitators to vaccine uptake have recently been reviewed, there is no comprehensive review of factors influencing subsequent adherence or completion, which is key to achieving vaccine effectiveness. This study identifies and summarises the literature on factors affecting completion of multi-dose vaccine schedules by adolescents. Methods Ten online databases and four websites were searched (February 2014). Studies with analysis of factors predicting completion of multi-dose vaccines were included. Study participants within 9–19 years of age were included in the review. The defined outcome was completion of the vaccine series within 1 year among those who received the first dose. Results Overall, 6159 abstracts were screened, and 502 full texts were reviewed. Sixty one studies were eligible for this review. All except two were set in high-income countries. Included studies evaluated human papillomavirus vaccine, hepatitis A, hepatitis B, and varicella vaccines. Reported vaccine completion rates, among those who initiated vaccination, ranged from 27 % to over 90 %. Minority racial or ethnic groups and inadequate health insurance coverage were risk factors for low completion, irrespective of initiation rates. Parental healthcare seeking behaviour was positively associated with completion. Vaccine delivery in schools was associated with higher completion than delivery in the community or health facilities. Gender, prior healthcare use and socio-economic status rarely remained significant risks or protective factors in multivariate analysis. Conclusions Almost all studies investigating factors affecting completion have been carried out in developed countries and investigate a limited range of variables. Increased understanding of barriers to completion in adolescents will be invaluable to future new vaccine introductions and the further development of an adolescent health platform. PROSPERO reg# CRD42014006765.

Japanese encephalitis (JE) virus is the leading cause of vaccine-preventable encephalitis and a significant cause of disability in Asia and the western Pacific. Many countries have introduced JE vaccination programs, including several low resource countries following WHO's prioritization of JE vaccination in 2006. We sought to characterize the public health impact of JE vaccination programs. JE case data and vaccination coverage rates, were requested from country health officials in 23 JE endemic countries and Chinese Taipei. Additional data were extracted from meeting presentations and published literature. JE incidence was compared before and after vaccination using a minimum three year period pre and post program introduction or expansion. Data suitable for analysis were available for 13 JE-endemic countries and Chinese Taipei, for either all age groups or for children aged under 15 years only. Five countries and Chinese Taipei introduced vaccine prior to 2006 and the all-age JE incidence was reduced by 73-100% in about 5-20 years following introduction. Six countries have introduced JE vaccine since 2006, and JE incidence in children aged younger than 15 years has been reduced by 14-79% as of 2015-2021. JE-specific data were unavailable before introduction in Thailand and Vietnam, but vaccination programs reduced acute encephalitis incidence by 80% and 74%, respectively. Even in the programs with greatest impact, it took several years to achieve their results. JE vaccination has greatly reduced JE in 13 JE-endemic countries and Chinese Taipei. Highest impact has been observed in countries that introduced prior to 2006, but it often took roughly two decades and substantial resources to achieve that level of success. For greatest possible impact, more recently introducing countries and funding agencies should commit to continuous improvements in delivery systems to sustain coverage after initial vaccine introduction.

To improve uptake of influenza vaccine in pregnancy, it is important to understand the factors that predict prenatal vaccination. The aim of this study was to test the capability of the theory of planned behavior, augmented with information constructs, to predict and explain influenza vaccination uptake in a sample of 600 pregnant individuals in Canada. A baseline survey at the start of influenza season assessed beliefs, norms, perceived control, and information-seeking behavior related to influenza vaccination in pregnancy, as well as respondent demographics. A follow-up survey at the conclusion of influenza season assessed self-reported influenza vaccine uptake as well as infant vaccination intentions. Multivariable analysis indicated that attitudes toward influenza vaccination in pregnancy, subjective norms, information seeking, and past vaccination behavior predicted intentions to be vaccinated, and intentions predicted vaccine uptake. Neither perceived control nor demographics were significant predictors of intentions or vaccine uptake. These findings suggest that presumptive offering of vaccination in pregnancy by health care providers, as well as patient and public health educational interventions, may be effective in communicating norms and strengthening positive attitudes and intentions concerning influenza vaccination in pregnancy, resulting in higher vaccine coverage.

Abstract Background Ghana introduced a 2-dose schedule rotavirus vaccine, Rotarix, into childhood immunization in 2012 but switched to a 3-dose schedule vaccine, Rotavac, in 2020 on account of programmatic advantages offered by the latter, including lower cost per fully immunized child and lower cold chain volume requirement. The objective of the study was to assess the effect of the vaccine switch on the trends of rotavirus vaccine uptake and health facility outpatient department (OPD) attendance due to diarrhea among children aged 1–11 months. Methods A retrospective analysis was conducted on childhood immunization and diarrhea surveillance data for 2018–2022. The uptake of the different rotavirus vaccine products and the proportion of health facility OPD attendance attributed to diarrhea, respectively, were compared between the pre- and postswitch study periods. Results The uptake of rotavirus vaccine was sustained following the switch. There were no significant differences in vaccination coverages (rota1, Rotarix coverage [94.3%], vs rota1, Rotavac coverage [95.3%]; P = .757; rota2, Rotarix coverage [91.3%], vs rota2, Rotavac coverage [92.7%]; P = .789). The proportions of health facility OPD attendance due to diarrhea were comparable (preswitch [12.4%] vs postswitch [12.1%]; P = .838). Conclusions Ghana's rotavirus vaccine switch yielded expected programmatic benefits without any untoward effects. The trends of vaccine uptake and reduction in diarrhea morbidity were sustained. These experiences and lessons from the rotavirus vaccine switch are vital for potential switches for other vaccines in the current immunization schedule to mitigate the annual vaccine expenditure.

Although myocarditis/pericarditis (MP) has been identified as an adverse event following smallpox vaccine (SPX), the prospective incidence of this reaction and new onset cardiac symptoms, including possible subclinical injury, has not been prospectively defined. The study's primary objective was to determine the prospective incidence of new onset cardiac symptoms, clinical and possible subclinical MP in temporal association with immunization. New onset cardiac symptoms, clinical MP and cardiac specific troponin T (cTnT) elevations following SPX (above individual baseline values) were measured in a multi-center prospective, active surveillance cohort study of healthy subjects receiving either smallpox vaccine or trivalent influenza vaccine (TIV). New onset chest pain, dyspnea, and/or palpitations occurred in 10.6% of SPX-vaccinees and 2.6% of TIV-vaccinees within 30 days of immunization (relative risk (RR) 4.0, 95% CI: 1.7-9.3). Among the 1081 SPX-vaccinees with complete follow-up, 4 Caucasian males were diagnosed with probable myocarditis and 1 female with suspected pericarditis. This indicates a post-SPX incidence rate more than 200-times higher than the pre-SPX background population surveillance rate of myocarditis/pericarditis (RR 214, 95% CI 65-558). Additionally, 31 SPX-vaccinees without specific cardiac symptoms were found to have over 2-fold increases in cTnT (>99th percentile) from baseline (pre-SPX) during the window of risk for clinical myocarditis/pericarditis and meeting a proposed case definition for possible subclinical myocarditis. This rate is 60-times higher than the incidence rate of overt clinical cases. No clinical or possible subclinical myocarditis cases were identified in the TIV-vaccinated group. Passive surveillance significantly underestimates the true incidence of myocarditis/pericarditis after smallpox immunization. Evidence of subclinical transient cardiac muscle injury post-vaccinia immunization is a finding that requires further study to include long-term outcomes surveillance. Active safety surveillance is needed to identify adverse events that are not well understood or previously recognized.

Immunization Information Systems (IIS) and surveillance data are essential for public health interventions and programming; however, missing data are often a challenge, potentially introducing bias and impacting the accuracy of vaccine coverage assessments, particularly in addressing disparities. This study aimed to evaluate the performance of 3 multiple imputation methods, Stata's (StataCorp LLC) multiple imputation using chained equations (MICE), scikit-learn's Iterative-Imputer, and Python's miceforest package, in managing missing race and ethnicity data in large-scale surveillance datasets. We compared these methodologies in their ability to preserve demographic distribution, computational efficiency, and performed G-tests on contingency tables to obtain likelihood ratio statistics to assess the association between race and ethnicity and flu vaccination status. In this retrospective cohort study, we analyzed 2021-2022 flu vaccination and demographic data from the West Virginia Immunization Information System (N=2,302,036), where race (15%) and ethnicity (34%) were missing. MICE, Iterative Imputer, and miceforest were used to impute missing variables, generating 15 datasets each. Computational efficiency, demographic distribution preservation, and spatial clustering patterns were assessed using G-statistics. After imputation, an additional 780,339 observations were obtained compared with complete case analysis. All imputation methods exhibited significant spatial clustering for race imputation (G-statistics: MICE=26,452.7, Iterative-Imputer=128,280.3, Miceforest=26,891.5; P<.001), while ethnicity imputation showed variable clustering patterns (G-statistics: MICE=1142.2, Iterative-Imputer=1.7, Miceforest=2185.0; P: MICE<.001, Iterative-Imputer=1.7, Miceforest<.001). MICE and miceforest best preserved the proportional distribution of demographics. Computational efficiency varied, with MICE requiring 14 hours, Iterative Imputer 2 minutes, and miceforest 10 minutes for 15 imputations. Postimputation estimates indicated a 0.87%-18% reduction in stratified flu vaccination coverage rates. Overall estimated flu vaccination rates decreased from 26% to 19% after imputations. Both MICE and Miceforest offer flexible and reliable approaches for imputing missing demographic data while mitigating bias compared with Iterative-Imputer. Our results also highlight that the imputation method can profoundly affect research findings. Though MICE and Miceforest had better effect sizes and reliability, MICE was much more computationally and time-expensive, limiting its use in large, surveillance datasets. Miceforest can use cloud-based computing, which further enhances efficiency by offloading resource-intensive tasks, enabling parallel execution, and minimizing processing delays. The significant decrease in vaccination coverage estimates validates how incomplete or missing data can eclipse real disparities. Our findings support regular application of imputation methods in immunization surveillance to improve health equity evaluations and shape targeted public health interventions and programming.