Diphtheria / Tetanus / Pertussis (acellular component) vaccine (adsorbed) injection pre-filled syringes / Haemophilus type b conjugate vaccine injection vials

BackgroundArmed conflict disrupts health systems and undermines routine immunization, contributing to excess morbidity and mortality. This systematic review examines empirical evidence on the impact of armed conflict on vaccination services and coverage, identifying patterns of disruption across geographic settings and conflict types.MethodsThis study followed PRISMA guidelines and was registered in PROSPERO (CRD420251064804). We searched seven databases for peer-reviewed and grey literature (1985-2025) reporting quantitative comparisons of vaccination coverage before and after conflict onset, or between conflict-affected and unaffected populations. Screening and data extraction followed standardized systematic review protocols, with dual validation of a subset of studies. Due to methodological heterogeneity across studies, a meta-analysis was not conducted.ResultsOf 8,043 citations screened, 33 met the inclusion criteria. Most focused on child immunization in settings across the Eastern Mediterranean (15, 45%) and African (12, 36%) regions. Data sources included household surveys (22, 67%) and health system records (8, 24%). Conflict exposure was most commonly measured using battle-related deaths (15, 45%). Analyses employing individual-level data were most common (10, 30%), followed by subnational administrative data (9, 27%). Nearly all studies (31, 94%) were observational or quasi-experimental. In 28 (85%) studies, conflict was associated with reduced vaccination coverage, sometimes exceeding 20% points for vaccines such as BCG, DTP, and polio. Declines were most pronounced in settings with civil war and moderate to high conflict intensity. Two studies reported localized increases in vaccination coverage, possibly due to targeted humanitarian interventions. Effect estimates were larger in studies using national or administrative-level data compared to those using household-level data, underscoring methodological variation as a key contributor to heterogeneity in reported impacts.ConclusionsArmed conflict is consistently associated with substantial declines in childhood vaccination coverage, most pronounced in civil war and military occupation settings and across conflicts with moderate-to-high annual BRDs. Regional disruptions were especially severe in the Eastern Mediterranean and sub-Saharan African regions. We found substantial variation in estimated effect sizes across analytic units (individual, household, region, country), suggesting that more aggregated data may better capture the broader impact of conflict on vaccination rates. Future research should incorporate standardized conflict and vaccination metrics to improve the generalizability of findings.

Abstract licence: CC BY

Background: Co-administration of vaccines can impact the immune response and safety. We aim to systematically review the current scientific literature and find evidence regarding the immunogenicity and safety of pneumococcal vaccines co-administered with common vaccines that are recommended for travelers, including hepatitis A, hepatitis B, yellow fever, tetanus, diphtheria, and acellular pertussis (Tdap), Japanese encephalitis, rabies, typhoid, or meningococcal (MCV) vaccine in adults (18 years or older). Methods: We followed the PRISMA 2020 guidelines and used the PICOS process to select the keywords. We searched PubMed, Web of Science, Scopus, EMBASE, and Google from 1 January 2000 to 30 June 2024. We included randomized controlled trials, non-randomized controlled trials, observational studies, case series, and case reports in adults, all published in English. Results: Out of 598 articles screened, 6 studies were included in our study. Three studies involved immunocompetent individuals, and three involved immunocompromised individuals. Co-administration of pneumococcal vaccine with Tdap or Hepatitis A in immunocompetent individuals was safe and immunogenic. Similar findings were reported for immunocompromised individuals when pneumococcal vaccines were co-administered with Tdap, hepatitis A, and hepatitis B. However, no reports investigated the co-administration of yellow fever, rabies, Japanese encephalitis, and typhoid. Two non-randomized studies in immunocompromised individuals had a high risk of bias. Conclusions: The studies collectively indicate that the co-administration of pneumococcal vaccines with Hepatitis A and Tdap vaccines in adult immunocompetent and immunocompromised individuals is safe and immunogenic. However, a knowledge gap remains, and further high-quality studies are needed, particularly due to the limited number of studies and the potential risk of bias.

Abstract licence: CC BY

BackgroundAcute lymphoblastic leukemia is the most prevalent childhood cancer and the leading cause of cancer mortality before the age of 20. Although therapeutic advances have significantly improved survival, children and adolescents treated for acute lymphoblastic leukemia remain vulnerable to infections, largely preventable by vaccination, due to humoral and cellular immune dysfunction induced by disease and treatment.Materials and methodsThis systematic review, based on electronic databases, aims to evaluate antibody levels associated with potential protective immunity against vaccine antigens for diphtheria, pertussis, tetanus, poliomyelitis, Haemophilus influenzae type b, measles, mumps, rubella, influenza, varicella-zoster virus, yellow fever, pneumococcal, and meningococcal diseases in children and adolescents treated for acute lymphoblastic leukemia after completion of chemotherapy.ResultsA total of twenty-four studies published between 1981 and 2023 were included, comprising 1110 children and adolescents. Protective antibody levels ranged from 11% to 97% for diphtheria, 0% to 90% for pertussis, 20% to 100% for tetanus, and 11% to 95% for poliomyelitis. Haemophilus influenzae type b, protection ranged from 16.7% to 100%. Viral vaccines also showed heterogeneous responses, with protection rates of 25-79% for mumps, 16-86% for measles, 35-98% for rubella, and 23-75% for varicella-zoster virus. Antibody responses to pneumococcal and meningococcal vaccines were consistently low, with protection rates of 5-38% for pneumococcal studies and 12% in a single meningococcal study.ConclusionsThis review found a consistent and clinically relevant loss of vaccine-induced immunity in children and adolescents treated for acute lymphoblastic leukemia. The recommendation of vaccine booster doses for this vulnerable population, irrespective of serological status, may represent a more practical approach to ensuring adequate post-chemotherapy treatment protection.

Abstract licence: CC BY

ObjectiveTo systematically review and critically appraise human evidence on potential health effects of aluminium adjuvanted vaccines.DesignSystematic review following PRISMA (preferred reporting items for systematic review and meta-analysis) 2020 guidelines.Data sourcesSix databases and trial registries were searched from inception to 3 March 2023 then updated to 27 November 2025. Reference lists of eligible studies were also screened.Eligibility criteria for selecting studiesHuman studies assessing health outcomes after aluminium adjuvanted vaccination, including randomised controlled trials, cohort studies, case series, and ecological studies. Investigational vaccines, case reports, and review articles were excluded.Data extraction and synthesisTwo reviewers screened studies (with AI assistance for the 2023-25 update), extracted data, and assessed risk of bias (using RoB 2.0, ROBINS-I, or an adapted tool for case series). Certainty of evidence was rated using GRADE (Grading of Recommendations Assessment, Development, and Evaluation).ResultsThe review included 59 studies (37 case series, 11 randomised controlled trials, nine cohort studies, two ecological studies). High quality evidence from randomised controlled trials and large cohorts consistently showed no association between aluminium adjuvanted vaccines and serious or long term health outcomes, such as asthma, autism spectrum disorders, or other chronic conditions. Studies on macrophagic myofasciitis were generally small and methodologically limited, and did not provide credible evidence of a causal association (very low certainty). Localised persistent nodules or granulomas were observed infrequently after diphtheria-tetanus-pertussis vaccines, consistent with delayed type hypersensitivity (ConclusionsCurrent evidence does not support causal associations between aluminium adjuvanted vaccines and serious or long term health outcomes. The most consistently documented reactions were persistent nodules or granulomas that are uncommon, local, and self-limited hypersensitivity reactions. These findings are broadly consistent with post-licensure surveillance findings. The predominance of methodologically limited studies for some outcomes highlights the need for higher quality research.Systematic review registrationPROSPERO CRD42023462831.

Abstract licence: CC BY-NC