All you need to know about vaccines approved in India

Covishield has been developed at the Pune-based Serum Institute of India (SII) with a master seed from pharma giant AstraZeneca and Oxford University.

Meanwhile, COVAXIN has been developed indigenously by the Hyderabad-based Bharat Biotech in collaboration with the Indian Council of Medical Research's National Institute of Virology (ICMR-NIV). The ICMR is India's apex medical research body at the forefront of the fight against COVID-19.

Covishield uses the replication-deficient chimpanzee viral vector (ChAdOx1) based on a weakened version of a common cold virus (adenovirus) containing the genetic material of the SARS-CoV-2 virus spike protein. The spike protein produced triggers an immune response that offers protection against future SARS-CoV-2 infections.

COVAXIN is an inactivated vaccine, i.e., it uses an inactivated or killed pathogen (SARS-CoV-2) to trigger an immune response.

SII submitted safety, immunogenicity, and efficacy data generated on 23,745 participants aged over 18 years from overseas clinical studies.

Covishield has been found to have an overall efficacy of 70.42%, according to trial data submitted by the SII.

SII CEO Adar Poonawalla had said last week that Covishield is "90-95% effective" if the two doses are given two-three months apart.

COVAXIN's efficacy is yet to be ascertained as its Phase III trials are still incomplete. The Phase III trials were commenced in November and so far, 22,500 out of 25,800 intended subjects have been vaccinated.

Phase I and II trials, conducted with 800 subjects, found that the vaccine had a "robust immune response," DCGI Dr. VG Somani said on Sunday.

Union Health Minister Dr. Harsh Vardhan had said on Saturday that one crore healthcare workers and two crore frontline workers will receive the vaccine in the first phase of vaccination free of cost.

The general public will likely end up paying roughly Rs. 500-600 for a shot of Covishield, as SII CEO Adar Poonawalla has said in the past.