A type 2 strain of polio virus (P2) found in a sewage sample from Mumbai in the last week of August may have triggered the investigations against vaccine-making company Bio-Med. The P2 strain was found in L ward (Kurla), during a routine environmental surveillance which involves collecting sewage samples from high-risk sites on a weekly basis.
P2 was eradicated globally in 1999. In April 2016, India stopped the Trivalent Oral Polio Vaccine (TOPV) containing live attenuated (weakened) P1, P2 and P3 strains and replaced it with bivalent vaccine containing P1 and P3. Finding P2 strain in its vaccine form thus raised concerns as the virus was no more in circulation even through the vaccines. “First and foremost, there is no reason to panic as the sewage sample had the vaccine virus and not the wild polio virus. Soon as we got to know about this, we have intensified the immunisation rounds in several areas”, said Dr. Archana Patil, Additional Director, Directorate of Health Services, Maharashtra. “The Centre on September 10 issued a circular to stop use of Bio-Med’s bivalent OPV which we implemented immediately”, she added.
“After we got to know about the P2 virus, we carried out a search with all doctors and centres who stock polio vaccines. We did not find any TOPV in the city. We are puzzled about where the contamination came from”, said Dr. Chandrakant Chiplunkar, assistant health officer, BMC.
