Written by Prabha Raghavan
, Edited by Explained Desk | New Delhi |
Published: July 18, 2020 8:41:33 am


coronavirus news, coronavirus vaccine, covid cure, coronavirus vaccine india, india covid vaccine, coronavirus vaccine human trials, india covid trials, indian express With Covaxin, the participants will be vaccinated twice in the first phase of trials, fourteen days apart. (AP Photo/File)

Bharat Biotech and Zydus Cadila kicked off human trials for their Covid-19 vaccine candidates this week, inoculating the first set of participants in what will be a closely watched race for an indigenous vaccine against the contagious virus.

What are these vaccines?

Bharat Biotech’s Covaxin is an “inactivated” vaccine, which is made using particles of the Covid-19 virus that were killed so that they would not be able to infect or replicate in those injected with it. Injecting particular doses of these particles serves to build immunity by helping the body create antibodies against the dead virus, according to the firm.

Zydus Cadila’s ZyCov-D is a “plasmid DNA” vaccine. DNA vaccines use genetically engineered plasmids–a type of DNA molecule–that are coded with the antigen (a toxin or substance given off by the virus) against which the immune response is to be built. The DNA sequence injected would match that of the virus, helping the body build antibodies against it.

When did the trials start?

Both Bharat Biotech and Zydus Cadila began vaccinating their first set of participants on July 15.

The first phase of the Covaxin trials are to be conducted on 375 participants across 12 clinical trial sites in the country, of which two–AIIMS Patna and PGIMS Rohtak–have begun the vaccination process.

The ZyCov-D phase I and II trials target 1,048 participants and are to be conducted at one site–Zydus Research Centre in Ahmedabad–according to the Clinical Trial Registry of India.

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What happens now?

The sites that have begun testing Covaxin would have to finish vaccinating a smaller number of people to ensure that it is safe to continue with the phase I trials in the first place.

For instance, AIIMS Patna is targeting a total of 18-20 participants in the first set. After it vaccinates this group with Covaxin, it will have to pause the enrollment for 7-10 days while it collects data on the vaccine’s safety from this group. This data will be submitted to a Data and Safety Monitoring Board that will study the information and decide whether it is safe to administer the vaccine in humans.

If there are no safety issues observed, the site will be allowed to continue enrollment and vaccinate more participants as part of the first phase of the trial.

It is unclear whether a similar procedure will be followed for ZyCov-D.

With Covaxin, the participants will be vaccinated twice in the first phase of trials, fourteen days apart.

ZyCov-D’s trials entail vaccinating the participants three times. The second vaccination will take place on the 28th day and the third on the 56th day.

How long will the trials take?

The first phase of the trials for Covaxin are expected to take over a month to complete, after which it is expected that the data from the first trial will be submitted to the Drug Controller General of India. Following this, it will move on to phase II trials. CTRI shows that both phases of the trial are expected to take around 15 months to complete.

ZyCov-D’s first phase of trials is expected to take nearly three months to complete, following which the vaccine will move on to the second phase. CTRI shows that both phases of the trials are expected to take a year to complete. However, the firm’s chairman, Pankaj Patel, had earlier stated that it expected the first two phases of the trials to be completed in three months.

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