FAQ: What Does Covaxin’s 81% Efficacy Mean? How Does It Work?

Covaxin’s Phase 3 trial results show 81% efficacy. Here’s everything you need to know about the homegrown vaccine.

3 min read
Covaxin was the first indigenously produced vaccine to be rolled out in India for public use.

On Wednesday, 3 March, Hyderabad-based vaccine manufacturer Bharat Biotech announced that the Phase 3 clinical results of their indigenously-made COVID-19 vaccine, Covaxin, showed an 81% efficacy in preventing COVID.

Covaxin, the first indigenously produced vaccine, has previously garnered criticism for being administered to front-line workers in large numbers before all phases of its clinical trials were completed.

And so, this announcement is especially significant in lifting a lot of the ambiguity surrounding the homegrown vaccine.

Talking to FIT, Dr Swapneil Parikh, Internal medicine specialist in Mumbai and author of ‘The Coronavirus: What You Need to Know About the Global Pandemic’, said, “It’s wonderful news that interim analysis from the Covaxin Phase 3 trial suggests the vaccine is efficacious. We need to wait for the pre-print to see the confidence in this data but this is great news for our country!”

While more data is expected, as the clinical trial will continue to further evaluate the efficacy of the vaccine, here's everything you need to know about Bharat Biotech’s Covaxin.

How does it work?

Covaxin is a whole microbe inactive vaccine. This means that the vaccine uses the killed version of the pathogen that causes the disease, like in the case of many traditional vaccines. They are made from viruses or bacteria that have been killed clinically and therefore they cannot cause diseases anymore, according to WHO.

The SARS-CoV-2 strain for Covaxin was isolated in NIV, Pune, and transferred to Bharat Biotech. The inactivated vaccine was then developed and manufactured in their High Containment facility in Hyderabad.

Other inactivated vaccines include hepatitis A, influenza, polio, and rabies among others.

What did previous trials show?

Covaxin had released Phase 1 and 2 data, back in November 2020, conducted in 755 participants, which demonstrated high safety profile of the candidate vaccine along with seroconversion rates of 98.3% and 81.1% on days 56 and 104 respectively.

The interim findings of the Phase 1 trial data published in Medrexiv, revealed promising results indicating a successful, tolerable vaccine. It showed success in inducing an immune response, and no serious adverse events in any of their 375 volunteers.

Similar findings were also recorded in a peer-reviewed interim report published by Lancet in January.

What about its efficacy?

The results of Phase 3 clinical trials show that the vaccine demonstrates an interim clinical efficacy of 81% in preventing COVID-19.

“COVAXIN® not only demonstrates high clinical efficacy trend against COVID-19 but also significant immunogenicity against the rapidly emerging variants.”
Dr Krishna Ella, Chairman & Managing Director, Bharat Biotech

How safe is it?

The company said that the interim analysis included a preliminary review of the safety database, which showed that severe, serious, and medically attended adverse events occurred at low levels and were balanced between vaccine and placebo groups.

The most common adverse event was pain at the site of infection, and as per the paper, this was resolved immediately.

What are its advantages?

Covaxin is stable at 2 to 8°C (refrigerated), much like Oxford AstraZeneca’s Covishield, making it suitable for transportation and storage in warmer countries like India.

The containers they are shipped in have a 28-day open vial policy, as a unique product characteristic, thus reducing vaccine wastage by approximately 10-30%.

What does it mean for India?

“This means India has a second proven efficacious vaccine,” says Dr Swapneil Parikh. “If Bharat Biotech is able to meet manufacturing targets of hundreds of millions of doses in 2021 this will be beneficial to not just India, but many LMIC countries.”

These results are likely to accelerate India’s already active vaccine drive.

“This news couldn’t have come at a better time as we have just started scaling out vaccine distribution for the general public. This is very welcome and exciting news,” says Dr Swapneil Parikh.

On March 1, Prime Minister Narendra Modi was administered the first dose of Covaxin.

Under what provision is Covaxin approved?

On January 3, the Drugs Controller General of India (DCGI) approved Covaxin for ‘emergency use’ under ‘clinical trial mode’. At the time the significant controversy was created, since Phase 3 trials were still ongoing and data was awaited.

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