Covaxin, a COVID-19 vaccine being developed by Bharat Biotech, showed long-term antibody and T-cell (immune) memory responses three months after the shot in phase 1 volunteers and tolerable safety outcomes in Phase 2 study, the city-based company has said, suggesting the antibodies may persist for six to 12 months.

In phase 2, it also showed enhanced humoral and cell-mediated immune responses and the results were found in the safety and immunogenicity clinical trial of the vaccine candidate.

Memory T cells are antigen-specific T cells that remain over a long term after an infection has been eliminated.

Covaxin, being developed in collaboration with the Indian Council of Medical Research and the National Institute of Virology, is now undergoing phase-3 trials.

In a double-blind, randomised, multi-centre phase 2 clinical trials, a total of 380 healthy children and adults were randomised and administered two vaccine formulations in as many doses (four weeks apart).

In a follow-up of the phase 1 trial, Covaxin (BBV152) produced high levels of neutralising antibodies that remained elevated in all participants three months (at day 104) after the second vaccination.

Based on these results, we hypothesise that BBV152 can generate antibodies that may persist for 6-12 months, Bharat Biotech said in a research paper on Covaxin.

The results from the phase 2 study show that both humoral and cell-mediated responses were observed. No neutralising antibody differences were observed between sexes and across age groups.

Covaxin was well tolerated in both dose groups with no serious adverse events, the research paper further said.