Characterization and Durability of COVID-19 Vaccine Induced Immune Responses in Healthcare/Frontline Workers

Rationale: Early in the covid-19 pandemic, it was unclear whether and how individuals and populations would develop protective and enduring immunity against SARS-CoV-2, either after infection or vaccination. It is still not clear what role might immune cellular responses play in the development of immunity to SARS-CoV-2 infection and what are the implications for vaccines? As T cells recognise and respond to viral antigens they produce many protective reactions and effector molecules. One such molecule is the cytokine interferon γ, secreted by CD4+ and CD8+ T cells and their memory cells. This can be measured means of documenting specific T cell responses to viral antigens. Published studies offered a strong evidence that T cell immune responses are sustained, even in the face of declining or undetectable antibodies, implying that some immunity persists. The evidence from new studies, interim results from phase III vaccine trials, and previous data from phase I and phase II trials support the notion that memory T cell responses to the vaccines, along with B cell antibody responses, should provide good and possibly enduring immunity to SARS-Cov-2. We propose to describe and characterize the humoral, innate and long-term adaptive immune responses and the neutralization potential generated by COVID-19 vaccination (Covaxin, Covishield) among healthcare and frontline workers.