Antimicrobial preservatives (APs) offer significant advantages when included in multi-dose vaccines (MDVs) and biologics. In addition to reducing medical waste and optimizing overall manufacturing efficiency, MDVs with APs increase global access to critical medicines and meet public health demands. Phenol, metacresol, benzyl alcohol, benzethonium chloride, thimerosal, and phenoxyethanol are currently the only APs included in FDA-approved biologics and WHO prequalified vaccines. The mechanisms of actions of these six APs, however, may limit their suitability for certain biologics, namely RNA-based vaccines. Novel antimicrobial agents, such as zinc salts and chitosan, may be considered for further investigation and potential use as alternative APs. Including APs in biologics gives rise to additional manufacturing considerations pertaining to drug product quality and stability. In addition, antimicrobial agents have not yet been tested or approved for use in RNA-based vaccines, which highlights important implications for access and shelf-life.
Melanoma has emerged as a major focus of cancer immunotherapy research because of its highly immunogenic nature and responsiveness to immune-based treatments. Therapeutic melanoma vaccines are designed to stimulate tumor-specific immune responses through the delivery of Tumor-Associated Antigens (TAAs), Tumor-Specific Antigens (TSAs), and personalized neoantigens. This narrative review provides an overview of current melanoma vaccine strategies, including peptide-based vaccines, dendritic cell vaccines, nucleic acid-based platforms such as mRNA, DNA, and viral vector vaccines. Recent advances in vaccine engineering and tumor genomics have accelerated the development of personalized neoantigen vaccines capable of targeting mutations unique to individual tumors. In parallel, Artificial Intelligence (AI) and Machine Learning (ML) are increasingly being incorporated into neoantigen identification pipelines to improve epitope prediction and optimize vaccine design. Combination strategies involving Immune Checkpoint Inhibitors (ICIs), particularly anti-PD-1 and anti-CTLA-4 therapies, have further enhanced interest in melanoma vaccines by helping overcome tumor-induced immune suppression and augment T-cell activation. In addition to reviewing vaccine mechanisms and emerging technologies, this manuscript examines the evolving clinical trial landscape through analysis of melanoma vaccine studies registered on ClinicalTrials.gov . Although many studies have reported encouraging safety and immunogenicity findings, challenges related to tumor heterogeneity, immune evasion, biomarker selection, and manufacturing complexity continue to limit widespread clinical implementation. Ongoing advances in computational immunology, biomaterial engineering, and precision oncology are expected to further refine melanoma vaccine development and improve therapeutic efficacy. Collectively, these innovations may help establish melanoma vaccines as an increasingly important component of future personalized cancer immunotherapy strategies.
Background:Persistent vaccination inequities affect Indigenous and hard-to-reach populations in Latin America and the Caribbean (LAC), yet evidence on effective interventions remains fragmented. Objectives:To synthesize evidence on the effectiveness and feasibility of interventions designed to improve vaccination coverage among Indigenous and hard-to-reach populations in LAC. Design:Systematic review and meta-analysis following PRISMA 2020 guidelines. Methods:We searched PubMed/MEDLINE, Scopus, Web of Science, Cochrane Library, Google Scholar, and PAHO/WHO repositories for studies published between January 2015 and March 2025. Eligible studies reported primary data on vaccination coverage among Indigenous, rural, migrant, or marginalized populations in LAC. Two independent reviewers performed screening, data extraction, and quality assessment (JBI tools). Random-effects meta-analysis was conducted for comparable outcomes, with subgroup analyses by population and intervention type. Feasibility was assessed across logistical, financial, and cultural domains using an implementation science framework. Results:Of 2750 records, 21 studies met inclusion criteria, representing 10 LAC countries. Interventions included community health worker (CHW) outreach (43%), mobile units (29%), school-based delivery (14%), digital reminders (10%), and culturally tailored campaigns (5%). Meta-analysis of 16 studies showed that individuals receiving interventions were 64% more likely to achieve complete vaccination (risk ratio (RR) = 1.64; 95% confidence interval (CI), 1.32-2.04). Effects were stronger for Indigenous populations (RR = 1.85; 95% CI, 1.42-2.25) than for other rural groups (RR = 1.45; 95% CI, 1.20-1.80). CHW outreach and mobile units showed the largest effects. Feasibility was highest for CHW and culturally adapted strategies due to community trust, low costs, and adaptability. Conclusion:Community-based, culturally grounded interventions, particularly those integrating CHW networks and Indigenous leadership, significantly improve vaccination coverage among hard-to-reach populations in LAC. These findings support scaling equity-centered models within national immunization policies.
Cervical cancer remains a primary cause of gynecologic oncology-related mortality globally, with a disproportionate burden in sub-Saharan Africa. The pathogenesis of the disease is fundamentally driven by persistent infection with high-risk human papillomavirus (HPV) genotypes, most notably HPV-16 and HPV-18. The evolution of prophylactic HPV vaccination has transformed preventive oncology, progressing from first-generation bivalent and quadrivalent formulations to the nonavalent vaccine, which extended protection to five additional oncogenic types. These vaccines, composed of L1 virus-like particles (VLPs), induce robust and durable humoral and cellular immune responses, leading to population-level reductions of up to 98% in vaccine-type infections and 80% in high-grade cervical lesions. To address persistent global health disparities, regionally produced, cost-effective alternatives such as Cecolin and Cervavac have been introduced to enhance accessibility within low- and middle-income countries. This shift toward broader coverage is further supported by the 2022 WHO recommendation for a single-dose schedule, aimed at optimizing resource-limited immunization programs. Current research is now pivoting toward next-generation candidates targeting the conserved L2 protein for pan-genotype protection, as well as therapeutic vaccines targeting E6 and E7 oncoproteins to clear established infections. However, achieving the WHO’s 2030 cervical cancer elimination targets remains contingent upon overcoming infrastructural, cultural, and informational barriers that hinder vaccine uptake. This review synthesizes the molecular composition and immunological mechanisms of current and emerging HPV vaccines, evaluating their clinical efficacy and the systemic strategies required to ensure equitable global access.
