Journal of Vaccine Research 2024, Vol.14, No.4, 170-182 http://medscipublisher.com/index.php/jvr 177 populations. Furthermore, maintaining the cold chain for live-attenuated vaccines like Dengvaxia is critical, as any break in this chain can compromise vaccine efficacy. Additionally, the requirement for multiple doses, as seen with Dengvaxia’s three-dose schedule, complicates adherence and full vaccination coverage (Flasche et al., 2016). Public perception also poses a significant challenge to vaccine deployment. The controversy surrounding Dengvaxia, where adverse events led to increased cases of severe dengue in seronegative individuals, has led to vaccine hesitancy and distrust in several countries. This issue is particularly pronounced in the Philippines, where the initial enthusiasm for Dengvaxia was followed by public outcry and legal actions when safety concerns emerged. This situation has made it difficult to gain public trust in subsequent dengue vaccination efforts and has highlighted the importance of clear communication about vaccine risks and benefits (Wichmann et al., 2017). 6.2 Impact on dengue incidence Despite the challenges, data from vaccination programs have shown a significant impact on dengue incidence and hospitalization rates in regions where the vaccine has been effectively implemented. In countries where Dengvaxia has been administered to seropositive individuals, studies have reported reductions in the number of symptomatic dengue cases and severe outcomes. For instance, in Brazil and Mexico, the introduction of Dengvaxia led to a noticeable decrease in hospitalization rates for dengue, particularly in the age groups targeted by the vaccination program (Hadinegoro et al., 2015). Moreover, the ongoing trials for TAK-003 have shown promising results, suggesting that widespread use of this vaccine could lead to a broader reduction in dengue incidence across diverse populations. The observed efficacy in both seropositive and seronegative individuals suggests that TAK-003 might offer a more universally applicable solution to reducing the dengue burden globally (Biswal et al., 2021). 6.3 Economic considerations The cost-effectiveness of dengue vaccination programs is a critical consideration for public health authorities, particularly in resource-limited settings where healthcare budgets are constrained. Economic evaluations of Dengvaxia have shown that, when used appropriately in seropositive individuals, the vaccine can be cost-effective by reducing the incidence of severe dengue and the associated healthcare costs. For example, studies in Southeast Asia and Latin America have indicated that targeted vaccination of seropositive individuals can lead to significant savings in healthcare costs by preventing hospitalizations and the long-term health impacts of severe dengue (Flasche et al., 2016). However, the initial costs of vaccine procurement and the challenges in achieving high coverage rates can be barriers to implementation, especially in countries with large, diverse populations. The cost-effectiveness of TAK-003, which has demonstrated broader applicability across different serostatus groups, may be more favorable, particularly if the vaccine can be integrated into existing immunization programs for children and adolescents. Ongoing economic analyses are essential to determine the long-term value of dengue vaccination programs and to support their integration into national immunization schedules (Prompetchara et al., 2020). 6.4 Case studies of implementation In the Philippines, the initial rollout of Dengvaxia was met with high coverage rates and public support. However, following the emergence of safety concerns, particularly regarding the increased risk of severe dengue in seronegative children, the program faced significant backlash, leading to a suspension of the vaccine's use and widespread public distrust in vaccination programs overall (Santos et al., 2021). This case highlights the importance of rigorous pre-vaccination screening and clear communication to manage public expectations and concerns (Wichmann et al., 2017). In contrast, Brazil’s more cautious approach, where Dengvaxia was introduced with stringent guidelines recommending its use only in individuals with confirmed prior dengue infection, has been more successful (Kallas et al., 2020). This targeted approach has led to a reduction in severe dengue cases and maintained public confidence in the vaccination program. Brazil's experience demonstrates the importance of aligning vaccine
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