NEW DELHI: Covaxin, the Indian Covid-19 vaccine, jointly developed by Bharat Biotech and the Indian Council of Medical Research (ICMR), has been shown to effectively protect animals from coronavirus.
These are the first results of animal challenge studies on a vaccine candidate from India and is good news for millions of people waiting for a vaccine to arrive in order to bring the pandemic to a halt.
The study has been carried out by the scientists of the National Institute of Virology. The findings, set to be published in an international journal, suggest that the vaccinated groups of rhesus macaques had significantly lowered disease burden compared to the placebo group -- which did not get the actual vaccine.
In animal challenge studies, the monkeys are first vaccinated and then deliberately exposed to a pathogen to assess the efficacy of a vaccine or a drug.
In this exercise by NIV scientists, twenty macaques were divided into four groups of five animals each. One group was administered a placebo while three groups were immunized with three versions of the vaccine candidates, derived from killed SARS CoV 2, at 0 and 14 days.
All the macaques were then challenged with coronavirus 14 days after the second dose. The protective response was observed with increasing antibodies from the third-week post-immunization.
“… the two-dose vaccination regimen of inactivated SARS-CoV-2 vaccine candidates was found to induce a strong immune response and protection of animals from the infection of SARS-CoV-2,” the authors have reported.
The presence of viral RNA was observed in the placebo group until 7 days post-infection. The vaccinated monkeys had no detectable viral RNA indicating the ability of the vaccine candidates to limit upper respiratory tract viral replication, a key factor determining virus transmission.
Also, viral RNA was not detected in lung fluids from day five post-infection suggesting that the vaccination hindered virus replication and enabled faster clearance from the lower airway, protecting the animals.
“Viral RNA was found in multiple organs in the placebo groups, but not in the vaccinated groups. The vaccinated groups had significantly lower disease burden compared to the placebo group,” says the latest report.
Significantly, no evidence of pneumonia — a common serious symptom of Covid-19 in patients needing hospitalisation -- was observed in vaccinated groups, unlike the placebo group.
Covaxin, among the three experimental Covid-19 vaccines under clinical trials in the country, is in phase 2 trial across 12 centres in 10 states as of now.
Sources involved in the trial say that it could take nearly a month before it can enter late-stage or phase 3 trials in which the vaccine can be tested on thousands of volunteers for population-level results.