A systematic review on vaccine developmental approaches: Evaluating efficacy, and addressing challenges of infectious diseases in the post-COVID-19 era.

Vaccination prevents millions of fatalities annually and works as one of the most effective and cost-efficient public health interventions. This systematic review critically evaluates vaccine development strategies in the post-COVID-19 era, focusing on platform technologies, delivery systems, and the regulatory and societal challenges that shape vaccine efficacy and accessibility. The COVID-19 pandemic redefined expectations for vaccine science, compressing traditional development timelines, and accelerating the adoption of novel platforms, such as mRNA and viral vectors. While these innovations significantly reduced global morbidity and mortality, they also exposed persistent barriers, including unequal distribution and widespread vaccine hesitancy fuelled by misinformation. This review evaluates the biochemical foundations of vaccine design, including antigen selection, adjuvant use, and delivery optimisation, alongside the emerging formulation strategies and vaccine-platforms integration. The review emphasises the need for continuous alignment between scientific progress and equitable access. By integrating historical context, technical advancement, and social determinants, this review highlights the imperatives for future vaccine strategies to be not only scientifically robust, but also globally inclusive and implementation ready. By positioning recent advancements within the historical timeline of vaccine science, this review argues that the post-COVID-19 era represents an acceleration of progress where speed, adaptability and global equity are essential for safeguarding the populations against current and emerging threats from the pandemics and localized infectious challenges in medical emergencies.