Sequential observation of antibody response pattern at 3 and 6 months following ChAdOx1 nCoV-19 vaccination among health care workers-A prospective single cohort study oleh Ponnu Jose, Ramesh Bhaskaran, Sreeraj Vijay, Priyanka Rajmohan, Aboobacker Mohammed Rafi, Unnikrishnan Uttumadathil Gopinathan, Joe Thomas, Susheela J Innah, Lucy Raphael, Chithra Valsan, Praveenlal Kuttichira