Amidst concerns over wild poliovirus (P2 strain) being found in a Hyderabad drain, the Union Health Ministry today said it was a vaccine derived virus and does not change the polio-free status of India. However, as a precautionary measure, the ministry will hold a special immunization drive in the high-risk areas of Telangana. "India continues to be polio free as the country has eradicated wild polio virus and the last case was seen on January 13, 2011 and it is more than 5 years that no wild polio virus has been detected," it said in a statement.
The Health Ministry said the detected polio virus strain, which was was found in a sewage sample collected near the Secunderabad railway station, is vaccine derived polio virus (VDPV). VDPV are rare strain of the polio viruses that have genetically mutated from the strain contained in the Oral Polio Vaccine (OPV). The OPV contains live virus particles that get excreted by babies who are given the vaccine and gets into the sewage. While the OPV protects children, these excreted virus particles can at times regain neurovirulence (the tendency or capacity of a microorganism to cause disease of the nervous system) including through contaminated drinking water, and can cause paralysis if consumed by humans.
"No children have been found to be affected by the detected VDPV isolate in the nearby areas. Last case of Wild Polio Virus Type 2 in country was reported 17 years back in 1999," the Ministry said. The special campaign will be held from June 20 covering high-risk areas of Hyderabad and Rangareddy districts of Telangana, where an estimated 300,000 children will be protected against polio using Inactivated Polio Vaccine (IPV). Under the special campaign, children between the age group of six weeks and three years will be given an additional dose of the injectable polio vaccine (IPV). Vaccination booths will be set up in the areas being covered in these campaigns.
"The special immunisation campaign will ensure all vulnerable children living in high-risk areas are given protection against polio," it said. It said that a rapid surveillance review of the area revealed that the population immunity against polio type 2 is high as trivalent oral polio vaccine (tOPV) was in use in the state until 24 April and two mass vaccination campaigns were conducted in January and February. "As per recent sample survey in the area, 94 per cent children were found to have received at least 3 doses of OPV.
Therefore, chances of its transmission in concerned area are unlikely," the ministry said. "Parents of children living in these areas will be encouraged to ensure that their children get the IPV dose from the nearest vaccination booth which will provide additional protection against all types of polio," it said. The last case due to wild poliovirus in India was detected on 13 January 2011 and the country was certified polio-free by WHO in March 2014. "The polio-free certification pertains to the absence of wild poliovirus and thus country remains polio-free," the ministry said.
It said the detection shows the robustness of the surveillance system and the willingness to detect any kind of polio virus even from the environment (sewage). "All cases of paralysis with sudden onset in children up to 15 years (which is called Acute Flaccid Paralysis or AFP) are picked up by the polio surveillance network. Each of these cases is followed up and their stool samples tested for poliovirus in WHO accredited laboratories. In addition, sewage samples are collected from over 30 sites spread across the country for poliovirus detection at regular intervals," it said between Jan 2015 and May 2016, a total of 14 sewage samples collected from different parts of the country tested positive for VDPVs.
"All of these have been responded to urgently and appropriately with polio vaccination campaigns. None of these VDPVs detected in the sewage infected any children, so far," it said. The response by the health authorities to the VDPV in Hyderabad is in accordance with World Health Organization protocols to mitigate any risk of spread of the virus. The Ministry said that strong measures have been put in place in India to mitigate the risk of an importation and spread of the virus from countries with continued circulation of polio virus. Intensive efforts are also being undertaken in India to improve routine immunization coverage that involves administering polio vaccines, in addition to other vaccines, to infants under the Universal Immunization Programme (UIP), it said.