Some sources simply equate the two. On the other hand, Covishield seems to be undergoing its own clinical trials. The statement by the Indian authorities calls it “Recombinant Chimpanzee Adenovirus vector vaccine (Covishield) encoding the SARS-CoV-2 Spike (S) glycoprotein with technology transfer from AstraZeneca/Oxford University” and refers to overseas clinical studies totaling 23 745 participants, presumably AZD1222 phase III clinical trials.
This all is very confusing. Are the two biologically equivalent substances produced by different factories, or different vaccines using the same core ideas?