Immunologic Responses to Single and Double Doses of COVID-19 Vaccines in Egyptians

The recent Coronavirus Disease 2019 (COVID-19), has caused a global pandemic, and development of safe, effective vaccines is mandatory to return back to pre pandemic life. Many vaccines have been developed and requested by the authorities after the emergency license issued. The main mechanism of protection is through humoral and cell-mediated immune responses that might reduce the potential for disease development or severity. Cytotoxic T cells clear virus-infected host cells and contribute to control of infection. Preliminary data are now available indicating safty and effecacy of different vaccines . The vaccines were tolerated, with induction of neutralizing antibodies and antigen-specific T cells against the SARS-CoV-2 spike protein. The aim of this work is to evaluate the immune responses in adults, aged 25-65 years, up to 8 weeks after vaccination with a single and double doses live inactivated (Sinopharm), mRNA (Pfizer/ Biontech) and viral vector (Oxford/AZ- ChAdOx1 nCoV-19) vaccines. The Th1- response ( interferon-γ and tumor necrosis factor-α cytokine secretion by CD4+ T cells) and antibody production predominantly of IgG1 and IgG3 subclasses as well as CD8+ T cells mono, polyfunctional and cytotoxic phenotypes, will be also measured.