Needle-free injection system delivery of ZyCoV-D DNA vaccine demonstrated improved immunogenicity and protective efficacy in Rhesus macaques against SARS-CoV-2.

The apprehension of needles related to injection site pain, risk of transmitting the blood borne pathogens and effective mass immunization have led to the development of needle free injection system (NFIS). Here, we evaluated the efficacy of the NFIS and needle injection system (NIS) for the delivery and immunogenicity of DNA vaccine candidate ZyCOV-D in Rhesus macaques against SARS-CoV-2 infection. Briefly, twenty rhesus macaques were divided into five groups (4 animals each) i.e., I (1 mg dose by NIS), II (2mg dose by NIS), III [1mg dose by NFIS], IV (2mg dose by NFIS) and V (phosphate-buffer saline). The macaques were immunized with the vaccine candidates/PBS intradermally on day 0, 28 and 56. Subsequently, the animals were challenged with live SARS-CoV-2 after 15 weeks of the first immunization. Blood, nasal swab, throat swab, and bronchoalveolar lavage fluid specimens were collected on 0, 1, 3, 5 and 7 days post infection from each animal to determine immune response and viral clearance. Amongst all the five groups, 2mg dose by NFIS elicited significant titers of IgG and neutralizing antibody after immunization with enhancement in their titers post virus challenge. Besides this, it also induced increased lymphocyte proliferation and cytokine response. The minimal viral load post-SARS-CoV-2 challenge and significant immune response in the immunized animals demonstrated efficiency of NFIS in delivering 2mg ZyCOV-D vaccine candidate. This article is protected by copyright. All rights reserved.