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Home >News >India >Even at 62% efficacy, Covishield may be a good bet for resource-constrained India to combat pandemic

NEW DELHI: Controversy over AstraZeneca plc's covid-19 vaccine clinical trial may allow Serum Institute of India to only receive regulatory clearance for its full-dose regimen which had 62% efficacy, but that may still help India and other resource-constrained countries combat the pandemic.

Serum Institute is manufacturing up to one billion doses of the vaccine, which has been jointly developed by AstraZeneca and University of Oxford. The Pune-based firm will market the vaccine under its brand Covishield after receiving regulatory approval.

“You may have a vaccine of 95% efficacy but you can give it to less than 50% of people who should be getting it, then that’s no good. But if you have a 60-70% efficacious vaccine that you are able to give to 90% of the people who should be getting it, it can have the same or better effect. We are so focussed on efficacy based on press releases, that we think that anything less than 90-95% is no good. But that’s not true," said Shahid Jameel, chief executive officer of The Wellcome Trust and DBT India Alliance.

Jameel said that the headline numbers in press releases have created unnecessary expectations among and competition between vaccines.

Despite the relatively stronger success of Moderna’s and Pfizer’s vaccine candidates, each of which had shown about 95% efficacy, the AstraZeneca vaccine had been considered a more important candidate due to the lack of requirement of freezers. Moderna’s and Pfizer’s mRNA vaccine candidates require -70 and -20 degree Celsius, while AstraZeneca’s vaccine needs simple refrigeration in the range of 2 to 8 degree Celsius.

The temperature factor is an important one for India, where frequent power cuts and lack of freezers make distribution, especially in rural areas, a major challenge, say experts.

Another major factor in favour Astrazeneca’s vaccine is the cost, which at about $3 per dose in COVAX, is a fraction of the cost of Moderna’s and Pfizer’s candidates, making the shots more affordable for governments, especially those of developing countries like India.

However, after the initial euphoria of AstraZeneca’s interim results on Monday, there has been scathing criticism about the British drugmaker and Oxford for failing to disclose enough data from its clinical trial.

On Monday, AstraZeneca and Oxford on Monday announced that an initial analysis of trials in the UK and Brazil showed it was on an average 70.4% effective in preventing covid-19. However, the researchers had tested the two dosing regimens, of which the vaccine was 90% effective when a lower dose regimen was used--half a dose was given first, followed by a full dose a month later.

The efficacy rate dropped to 62% when two full doses were given one month apart.

AstraZeneca’s management has called the strong efficacy data that resulted from the error as “serendipity", especially because the efficacy rate was 62% when two full doses were given to participants.

Experts expressed skepticism about the vaccine’s 90% effectiveness in participants who were accidentally given a lower dose than intended. The lower dose has been tested on about one-fourth the total participants that the full dose was tried.

“Serendipity has its uses but (it) would be good to know more about what happened and why. Evaluating dosing and intervals is a key part of vaccine development, (and it) should not be by accident," Gagandeep Kang, professor at Vellore’s Christian Medical College (CMC), had tweeted on Wednesday.

Serum Institute itself is conducting a phase 2 and 3 bridging study for Covishield and expects the trial to complete in December. The company was planning to launch the vaccine in January after receiving approval by the end of this year.

However, Kang expects that the world’s largest vaccine manufacturer may be unable to approach the Drug Controller General of India with the 90% efficacy data that was achieved by AstraZeneca for the vaccine, when the first dose was half of the regular final dose, but can ask for an equivalent of emergency use authorisation based on the 62% efficacy, Kang said in another tweet.

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