• Anusreeraj R S
• Ankit Singh

The COVID-19 pandemic, caused by the SARS-CoV-2 virus, has been one of the most catastrophic global health crises of the 21st century. Since its emergence in late 2019, the disease has spread rapidly worldwide, resulting in immense morbidity, mortality, and socioeconomic disruption. The pandemic has placed an unprecedented strain on healthcare systems, economies, and daily life. Understanding its origin, spread, and impact is crucial for appreciating the significance of vaccination and serological studies in evaluating long-term immunity. The first cases of COVID-19 were reported in December 2019 in Wuhan, Hubei province, China. Initially identified as a cluster of pneumonia cases with unknown etiology, the disease was later confirmed to be caused by a novel coronavirus. On January 7, 2020, the virus was officially identified as SARS-CoV-2, and its genome was sequenced soon after. The rapid human-to-human transmission led to the disease spreading beyond China, with international cases being reported by mid-January 2020. The World Health Organization (WHO) declared COVID-19 a Public Health Emergency of International Concern (PHEIC) on January 30, 2020, emphasizing the need for global preparedness. Despite efforts to contain the virus, COVID-19 continued to spread, and by March 11, 2020, the WHO declared it a pandemic. By this time, multiple countries had reported significant outbreaks, and global travel restrictions, lockdowns, and emergency healthcare measures were being implemented. Virology and Pathogenesis of SARS-CoV-2. SARS-CoV-2 belongs to the family Coronaviridae and is closely related to other human coronaviruses, such as SARS-CoV (which caused the 2002-2003 SARS outbreak) and MERS-CoV (Middle East Respiratory Syndrome). The virus primarily infects human cells via the angiotensin-converting enzyme 2 (ACE2) receptor, which is highly expressed in the respiratory tract, gastrointestinal tract, and several other organs. The spike (S) protein of SARS-CoV-2 plays a crucial role in viral entry into host cells. This protein binds to ACE2 receptors, facilitating membrane fusion and viral replication. Once inside the host, the virus hijacks the cellular machinery to produce new virions, leading to widespread inflammation and an immune response. The severity of COVID-19 varies among

"The Durability of Vaccine-Induced Immunity: Navigating the Challenges of COVID-19 Variants and Future Pandemic Preparedness – A Systematic Review ", International Journal of Emerging Technologies and Innovative Research (www.jetir.org), ISSN:2349-5162, Vol.13, Issue 1, page no.e736-e739, January-2026, Available :http://www.jetir.org/papers/JETIR2601500.pdf

"The Durability of Vaccine-Induced Immunity: Navigating the Challenges of COVID-19 Variants and Future Pandemic Preparedness – A Systematic Review ", International Journal of Emerging Technologies and Innovative Research (www.jetir.org | UGC and issn Approved), ISSN:2349-5162, Vol.13, Issue 1, page no. ppe736-e739, January-2026, Available at : http://www.jetir.org/papers/JETIR2601500.pdf