Impact of Covishield Vaccination in Terms of SARS CoV-2 Neutralizing Antibody Expression

The vaccination efficacy can indirectly be assessed through the quantification of neutralizing antibodies. Very few data are available on Covishield efficacy in terms of neutralizing antibody expression upon vaccination. This study is focused on profiling of neutralizing antibody expression during and after the Covishield two shot vaccination and observing COVID-19 infection in vaccinated participants during the period. SARS CoV-2 neutralizing antibody concentrations in samples were estimated using electrochemiluminescence immunoassay kit for Lifotronics eCL8000. The sampling had been done sequentially at 45th, 85th day after 1st dose and 15th day after 2nd dose Covishield vaccination. Parallelly, in order to confirm the total SARS CoV-2 IgG response in COVID-19 infection, measured the IgG using SARS CoV-2 IgG lateral flow immunoassay test kit. The subjects previously infected with COVID-19 before 1st dose vaccination demonstrated high neutralizing antibody (> 10AU/ml). In COVID-19 uninfected subjects, there was a sudden incline in neutralizing antibody after the 2nd dose. Infection with SARS CoV-2 between 1st and 2nd dose of Covishield vaccination implicate that the level of neutralizing antibody in serum after 1st dose was not adequate to combat the virus and prevent infection. We observed COVID-19 infection in participants even after 2nd dose of vaccination. Interestingly, there was no protection against SARS CoV-2 even with a high neutralizing antibody expression of 188.5 AU/mL after the 2nd dose. Findings of Covishield efficacy in different cohort samples before and after 2 doses of Covishield vaccination provide impetus for improvement or development of next generation vaccines.