The researchers found that Covaxin, an inactivated whole-virion vaccine, induces strong immune memory against SARS-CoV-2 and variants of concern that persists for at least 6 months after vaccination, and induces memory T cells that can robustly respond to variants. This can help control the viral load and thereby reduce the severity of the disease. The BBV152/Covaxin vaccine is based on the Asp614Gly variant and is formulated with a Toll-like receptor (TLR) 7/8 (imidazoquinoline) agonist molecule adsorbed onto alum. It was the first alum-imidazoquinoline adjuvanted vaccine manufactured in India and received emergency use authorization from the WHO for use in a large population.
Although data from clinical trials on vaccine efficacy were available, important questions remained unanswered, particularly regarding evidence-based policy making. These included whether the vaccine induces immune memory, how long vaccine-induced memory persists, and whether these memory responses are able to persist against SARS-CoV-2 variants.In multi-institutional collaboration with THSTI, Faridabad, AIIMS, New Delhi, ESIC Medical College, Faridabad, LNJP Hospital, New Delhi, LJI, LA Jolla, Dr. Nimesh Gupta and group at the National Institute of Immunology (NII), New Delhi examined 97 unexposed SARS-CoV-2 subjects who received the vaccine up to 6 months after the 2-dose vaccination. Vaccine-induced responses were compared with immune memory in 99 individuals recovered from mild COVID-19.
A study supported under the IRHPA-COVID-19 Special Challenge by the Science and Engineering Research Council, a statutory body of the Ministry of Science and Technology, found that the vaccine produced antibodies against the Spike, RBD and nucleoprotein of the virus, just as in viral infections. However, analyzes of both binding and neutralizing antibodies revealed reduced recognition of variants of interest such as Delta (India), Beta (S. Africa) and Alpha (UK).
This study showed that the vaccine is able to induce memory B cells. They found this satisfactory because antibodies can decline over time, but these memory B cells can replenish antibodies against the virus whenever needed. Their study provided the first ever evidence of the detailed features of immune memory generated in humans in response to an inactivated viral vaccine.
The team also found that the vaccine showed the potential to produce SARS-CoV-2-specific T cells. Importantly, unlike antibodies, T cell efficacy against the variants was well preserved. These virus-specific T cells were also present in the central memory compartment and persisted up to 6 months after vaccination. SARS-CoV-2 variants can affect vaccine-generated antibody responses; however, T cell responses will be available for a strong response against the variants. This is important knowledge for evidence-based policy making about the future use of Covaxin.
For more read: https://doi.org/10।1038/s41564-022-01161-5
