Explanation: What the phase 3 data says on the Covaxin Bharat Biotech vaccine

Covaxin, the vaccine manufactured by Bharat Biotech, has shown universal temporary clinical effectiveness of 78 percent, and 100 percent effectiveness against severe Covid-19 disease in phase 3 trials, the company and the Medical Research Council of India (ICMR) announced on Wednesday.

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Vaccine and the study

Covaxin, the country’s first indigenous Covid-19 vaccine, was developed with seed strains received from the National Institute of Virology (NIV), using Virion All Inactivated Vero Cell platform technology. Inactive vaccines do not duplicate; they contain a dead virus, which is incapable of infecting humans but has the ability to trigger the immune system to respond defensively against infection.

The vaccine received DCGI approval for phase 1 and 2 human clinical trials in July last year, and was submitted through Emergency Use Authorization (EUA) under clinical trial mode.

A phase 3 clinical trial, jointly funded by ICMR, enrolled 25,800 participants aged 18 to 98, including 10 percent over the age of 60, and an analysis was conducted 14 days after the second dose.

Results of provisional analysis

The results of the Covaxin phase 3 interim analysis are based on more than 87 symptomatic cases of Covid-19. Due to the recent surge in cases, 127 symptomatic cases were recorded, leading to a point estimate of a 78 percent vaccine efficacy against mild, moderate and severe Covid-19 disease, Bharat Biotech and ICMR said in a press release.

Effectiveness against severe Covid-19 disease was 100 percent with an effect on hospital admissions. Efficacy against asymptomatic Covid-19 infection was 70 percent, suggesting reduced transmission in Covaxin recipients.

The safety and effectiveness results of the final analysis will be available in June, and the final report will be submitted to a peer-reviewed publication, said Bharat Biotech and ICMR.

Based on meeting the success criteria, placebo recipients have now become eligible for two doses of Covaxin, said Dr. Krishna Ella, chairman and managing director of Bharat Biotech. “The efficacy data against severe Covid-19 and asymptomatic infections is very significant, as this helps to reduce the number of hospitalizations and disease transmission respectively,” he said.

Works against variations

Scientists at ICMR-NIV reported isolating and culturing all variants of concern – B.1.1.7 (UK variant), B.1.1.28.2 (Brazilian variant), B.1351 (South African variant) and the strain a double mutant B .1.617 (E484Q and L452R) found in some parts of the country – and which showed the potential of neutralizing Covaxin against variants in the UK and Brazil.

While data for the South African variant were being produced, Covaxin was found to effectively neutralize the double mutant strain, NIV scientists say. “The tireless efforts of our scientists at ICMR and BBIL (Bharat Biotech) have led to a truly effective international vaccine … Covaxin works well against most variants of SARS-CoV-2,” said ICMR Director General, Professor Balram Bhargava.

Minimal infection after infection

About 1.1 crore of the total doses administered in India so far have been Covaxin; 93.56 lakh of these have been first doses. Recipients of 0.04 percent (4,208) rarely received a positive result for Covid-19 after receiving the first dose of Covaxin, Dr Bhargava said.

Of the 17.37 lakh beneficiaries who received the second dose of Covaxin, 695 caught the “cutaneous infection after vaccination”, almost the same percentage as those after the first dose.

For Covishield, which has by far been the dominant vaccine, these numbers were 0.02 percent (17,145 out of 10.03 crore) for the first dose, and 0.03 percent for the second dose (5,014 positive out of 1.57 crore), according to government figures.

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Increase capacity

Suchitra Ella, joint managing director of Bharat Biotech, said efforts are under way to further develop Covaxin, with clinical trials underway in India and worldwide to evaluate its safety and immunogenicity in younger age groups, the effect of booster doses , and its protection against SARS-CoV- 2 variants.

More than 60 countries worldwide have expressed interest in Covaxin, and several countries have received Emergency Use Authorizations, the company said.

“Our development efforts have been transparent and published in six peer-reviewed journals, with additional publications in the process,” he said in the press release.

“The capacity expansion has been implemented across a number of facilities in Hyderabad and Bangalore to reach ~ 700 million doses a year, one of the largest production capacities for inactive viral vaccines worldwide.”

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