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Bharat Biotech releases Phase-III Data for Covaxin
In a previous article, we had covered how vaccines are developed-
In the initial stage, each vaccine must undergo an evaluation to ascertain which antigen must be used to evoke an immune response. This is the pre-clinical stage and does not involve humans. It is first tested in animals, and its safety and potential to prevent disease are evaluated. Then, the three phases of clinical trials begin.
In Phase-I, a small group of young and healthy volunteers is given varying levels of vaccine doses. This is done to determine the highest level of dosage that can be given without inducing any negative side effects.
In Phase-II, several hundred volunteers are tested to determine further whether an immune response is being generated and if the vaccine is safe. Participants in this stage have similar characteristics compared to the group for which the vaccine is intended. Multiple trials are involved in this phase with different groups and combinations of the vaccine.
Finally, in Phase-III, a much larger group (thousands of volunteers) is involved. The volunteers are divided into two groups; while one is given the vaccine, the other is given a placebo. Both the scientists and the volunteers are shielded from knowing whether they have been administered a placebo or the vaccine itself. This is known as blinding. Once the trial is completed, the data is ‘unblinded’ and scrutinised for efficacy. The process can be better explained through the example of Pfizer’s vaccine.
Pfizer enrolled 43,661 volunteers for its Phase-III trial, of which 41,135 received a second dose. A total of 170 people got infected with COVID, of which 162 were part of the group which received a placebo, while only 8 belonged to the group which received the vaccine. The variance is large enough to prove that the vaccine was indeed efficacious, but by how much? About 0.74 % of those who received the placebo contracted COVID (162/22,000), while only 0.036 % (8/22,000) of those who received the vaccine did so. Using this, we can calculate the relative risk by dividing 0.036 % by 0.74 %, which gives us 4.9%. This means people in the vaccinated group have about 5 % of the risk of contracting COVID than people in the placebo group, implying that the vaccine has a 95 % efficacy.
INDIA’S COVID VACCINE ROLLOUT AND VACCINE ‘MAITRI’ – ALL YOU NEED TO KNOW
In the case of Covaxin, the clinical trials were conducted between November 16, 2020 to January 7, 2021, among 25,798 participants. Out of this, 24,419 participants received either the vaccine or the placebo. As per the data, 130 symptomatic infections were detected in an analysis of 16,973 participants, of which 24 occurred in the vaccine group and 106 in the placebo group. The overall vaccine efficacy was found to be 77.8%. The vaccine has also shown 65.2% efficacy against the Delta variant, which ravaged India in April and May. Further, the vaccine has shown 93.4% efficacy against severe COVID.
Zydus Cadila seeks Emergency-Use Authorisation for its vaccine ZyCov-D
Zydus Cadila, an Ahmedabad-based firm, announced that it had applied for Emergency-Use Authorisation (EUA) for its needleless, three-shot vaccine, ZyCov-D. If approved, it will be India’s second home-grown vaccine after Covaxin and fifth overall to be authorised for use in India after Covaxin, Covishield, Sputnik V, and Moderna. The vaccine has undergone all three phases of clinical trials, and an efficacy of 66.6% for symptomatic COVID-19 cases was observed. Further, the vaccinated group reported no moderate or severe case, suggesting that the efficacy against moderate to severe COVID-19 is 100%. The primary advantage of the vaccine is the number of adolescents (1000) who were part of the Phase-III trials. Until now, the vaccines available can be used only for the adult population. However, in the case of ZyCOV-D, the vaccine was found to be safe and well-tolerated for the age group 12-18
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