NEW DELHI: The Resident Doctors' Association (RDA) of the Ram Manohar Lohia Hospital here on Saturday requested the medical superintendent to vaccinate them with Oxford Covid-19 vaccine Covishield. In a letter to the medical superintendent, the association said the resident doctors were "a bit apprehensive" about Covaxin and might not participate in the immunisation drive in large numbers thus defeating the purpose of the exercise which began in the country on Saturday. "We have come to know that the Covid-19 vaccination drive is being conducted by the hospital today. Covaxin manufactured by Bharat Biotech is being preferred in our hospital over Covishield manufactured by Serum Institute.