Adverse events were not seen in animals immunized with a two-dose vaccination regimen of Bharat Biotech’s Covaxin, the company’s vaccine candidate to protect people from the coronavirus disease (Covid-19), shows the animal study data published by one of India’s two Covid-19 vaccine candidates currently in human trials.

The vaccine, being developed in partnership with the Indian Council of Medical Research is in phase 1/2 of human clinical trials, but the results of the animal study had not been released.

The study also substantiated the immunogenicity of the vaccine candidate — showing that it offered extensive safety and generated effective immune responses against the target virus.

“…we have developed and assessed the protective efficacy and immunogenicity of an inactivated SARS-CoV-2 vaccine (BBV152) in rhesus macaques (Macaca mulata). Twenty macaques were divided into four groups of five animals each. One group was administered a placebo while three groups were immunized with three different vaccine candidates at 0 and 14 days…” a pre-print paper on the study, published on Research Square said.

All the macaques were exposed to SARS-CoV-2 14 days after the second dose was administered. According to the data, the protective response was observed with increasing SARS-CoV-2 specific IgG and neutralizing antibody titers from the third week post-immunization. Immunoglobulin G (IgG) is a long-lasting antibody that develops at least a week after exposure to a virus.

“Viral clearance was observed from bronchoalveolar lavage fluid, nasal swab, throat swab, and lung tissues at seven days post-infection in the vaccinated groups. No evidence of pneumonia was observed by histopathological examination in vaccinated groups, unlike the placebo group which showed features of interstitial pneumonia and localization of viral antigen in the alveolar epithelium and macrophages by immunohistochemistry. Data from this study substantiate the immunogenicity of the vaccine candidates…” the paper added.

Bharat Biotech initiated phase-1 clinical trials of Covaxin across the country on July 15, in the form of a randomized, double-blind, placebo-controlled clinical trial in 375 volunteers in India. Companies can launch such studies only after presenting drug regulators with pre-clinical studies (usually on animals) that show safety and efficacy.

The company is developing the vaccine in collaboration with the Indian Council of Medical Research (ICMR) that isolated the virus strain at its National Institute of Virology in Pune, and transferred it to the company on May 9.

The indigenous, vaccine candidate, based on an inactived virus, is being developed and manufactured in Bharat Biotech’s BSL-3 (Bio-Safety Level 3) High Containment facility located in Genome Valley, Hyderabad, India.

Covaxin got the Drug Controller General of India’s approval for Phase I/II clinical trials on June 29.

“Only after department’s subject experts studied the animal trials data and were satisfied with the results that the permission for human trials was granted. The process is being closely followed as everyone is waiting for a vaccine against Covid-19, and we have to ensure that what comes out is safe and effective after going through robust regulatory processes,” said a senior official in the drug regulator who asked not to be named.

The other indigenous vaccine in human trials is being developed by Zydus Cadila.