Smallpox has been eradicated globally since 1980 due to a successful worldwide vaccination campaign led by the World Health Organization (WHO), and this eradication is also reflected in India. In contrast, diphtheria and chickenpox still occur in India, with diphtheria being a vaccine-preventable disease still reported among unvaccinated populations, and chickenpox being endemic due to low immunity levels in the population despite the availability of vaccines. Understanding the impact of immunization strategies and public health initiatives is crucial in tracing the disease landscape and status within a country for the UPSC Prelims context.