Hyderabad, Apr 2 (UNI) Hyderabad-based Bharat Biotech, a global leader in vaccine and biotherapeutic innovation, on Tuesday announced it has collaborated with Bilthoven Biologicals B.V. (BBio), a wholly owned subsidiary of Serum Institute of India (SII) Private Limited, based in the Netherlands, to further strengthen the production and supply security of oral polio vaccines (OPV).