Demographic changes significantly influence the vulnerability of societies to pandemics by shaping patterns of exposure, transmission, susceptibility, and response capacity. In the context of population and sustainable development, demographic dynamics such as population growth, ageing, urbanization, migration, changes in household structure, and population density interact with economic, social, and environmental factors to increase the risks and impacts of pandemics. Understanding these linkages is essential for designing sustainable and resilient public health systems. One of the most important demographic factors is population growth. Rapid population growth, particularly in low- and middle-income countries, places immense pressure on health systems, housing, sanitation, water supply, and other basic services. When the size of the population increases faster than the expansion of infrastructure, overcrowded living conditions become common, especially in urban slums and informal settlements. Such environments facilitate the rapid spread of infectious diseases due to close physical proximity, shared sanitation facilities, and limited access to clean water. During a pandemic, the high density of susceptible individuals in confined areas accelerates community transmission and overwhelms health services. Urbanization is another major demographic trend that heightens vulnerability. The world is increasingly urban, with a significant proportion of the population living in cities. While urban areas offer better access to health care and economic opportunities, they also serve as hubs of intense social interaction and mobility. High population density in cities, extensive use of public transport, crowded markets, and large workplaces create ideal conditions for infectious agents to spread. Megacities connected through global travel networks act as gateways for pathogens, enabling local outbreaks to become global pandemics in a short period. Unplanned urban growth, inadequate housing, and environmental degradation further compound these risks. Population ageing also plays a critical role in pandemic vulnerability. Many countries are experiencing a demographic transition characterized by declining fertility and increasing life expectancy, leading to a higher proportion of elderly individuals. Older populations are generally more susceptible to severe outcomes from infectious diseases due to weakened immune systems and a higher prevalence of chronic conditions such as diabetes, cardiovascular diseases, and respiratory illnesses. Pandemics like COVID-19 have demonstrated that countries with a large elderly population experience higher mortality rates. Moreover, long-term care facilities and nursing homes, where many elderly people reside in close quarters, can become hotspots for infection. At the same time, countries with a youthful population face different but equally important challenges. In such contexts, large numbers of young people may live in densely populated households, attend schools, or work in informal sectors where social distancing is difficult. Young populations often have higher mobility rates and may act as carriers of infection, even if they experience milder symptoms. In addition, limited awareness