Scientists have found that Covaxin may help control the virus load of SARS-CoV-2 and its variant, thereby reducing disease severity. It is a whole-virion inactivated vaccine that induces robust immune memory to SARS-CoV-2 and variants of concern that persist for at least 6 months after vaccination and induces memory T cells that can respond robustly against the variants.
Why are we studying Covaxin?
Covaxin or BBV152 vaccine is based on an Asp614Gly variant and formulated with a toll-like receptor (TLR) 7/8 agonist molecule (imidazoquinolin) adsorbed to alum. It was the first alum-imidazoquinolin adjuvanted vaccine produced in India and received emergency use authorization from WHO for use in a large population.
Although the clinical trial data were available for the vaccine efficacy, critical questions remained unanswered for the evidence-based policymaking, such as;
– Whether the vaccine induces immune memory,
– How long the vaccine-induced memory persists; and
– Whether these memory responses are able to sustain against the SARS-CoV-2 variants.
What does the study say?
The study found that the vaccine produces antibodies against Spike, RBD, and Nucleoprotein of the virus, just like in virus infection. However, analyses of both the binding and neutralizing antibodies revealed a reduced recognition of variants of concern like Delta (India), Beta (S. Africa), and Alpha (UK).
It shows that the vaccine is capable of inducing memory B cells and the team found this satisfying because antibodies may decline with time. Still, these memory B cells can replenish antibodies against the virus, whenever required.
Team Behind this study
The study was conducted by THSTI, Faridabad, AIIMS, New Delhi, ESIC Medical College, Faridabad, LNJP Hospital, New Delhi, LJI, LA Jolla, Dr. Nimesh Gupta and group in a multi-institutional collaboration at the National Institute of Immunology (NII), New Delhi.
The team investigated 97 SARS-CoV-2 unexposed individuals who had received the vaccine, up to 6 months after 2-dose vaccination. The vaccine-induced responses were compared with the immune memory in 99 individuals who recovered from mild COVID-19. It was also supported under the IRHPA-COVID-19 special call by the Science and Engineering Research Board, a statutory body of the Department of Science and Technology.