India formally approved the coronavirus vaccines developed by Oxford-AstraZeneca (and made by Serum Institute of India in India) and Bharat Biotech for emergency roll-out on Sunday. The decision comes at a time of growing urgency as a mutant new strain threatens to make the pandemic harder to control. While the two doses will in no doubt improve India’s vaccination drive, the approvals by the Drugs Controller General of India leave several unanswered questions. It has chosen to green-light Bharat Biotech’s Covaxin, albeit with some riders, despite the fact that the candidate has not yet demonstrated how effective it is in preventing disease, and more importantly, its safety performance — according to latest company disclosures — has only been judged in limited numbers, that too over a short duration.
The candidate uses a tried-and-tested technique for making vaccines. The premise is simple: an inactivated Sars-Cov-2 virion is used to teach the recipient’s immune system how to combat a live pathogen. Early stage trials showed the vaccine did not cause any serious side effects and, as most inactivated virus vaccines today are, was safe. It also triggered “a robust immune response”. While this is encouraging, there are important caveats: this data, released on December 23, is yet to undergo peer review, relates only to findings in 190 people, and did not include anyone above the age of 65. The finding that it led to volunteers developing antibodies also does not automatically translate into protection from disease. That test is in determining the efficacy rate, which is indeed why the world had to wait for so long for its first successful candidates.
Vaccine makers give thousands of volunteers in phase III trials the dose or a placebo and wait to see who develops infections. If, for instance, infections are lower by 50% in the vaccinated group, the efficacy rate comes to 50% — the globally accepted benchmark for success. Oxford-AstraZeneca took nearly six months to determine this; Pfizer-BioNTech and Moderna almost four months. In contrast, Covaxin’s late-stage trials began only one-and-a-half month ago, its efficacy rate is unknown, and the period may be too short to map all possible side-effects. Authorities indicated that Covaxin will be used only if there is a shortage and if the new mutation takes hold. But Bharat Biotech and the regulators must now speed up the disclosures around the vaccine – people who receive it have the right to know how effective and safe it is.
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