Dr. Naveen D. Kini

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The recent Oral Polio Vaccine controversy

Posted by Naveen Kini on October 2, 2018 at 6:40 AM

Recent news articles in the newspapers about defective polio drops manufactured by a pharma company have created confusion and apprehension in the minds of the public. Let me clarify a few facts


What is the controversy?


India has reached zero transmission status of Wild Polio Virus (WPV) Types 1, 2 and 3 (which cause the paralytic disease Polio in children). But even then, regular surveillance is conducted to watch out for recurrence of this virus (called the AFP Surveillance Program). They routinely check stool samples of children for polio viruses (both disease causing and vaccine strains). During one such surveillance, the vaccine strain (Polio vaccine virus (Sabin) Type 2) was detected in the stools of children in Uttar Pradesh. This was traced back to the contamination of Bivalent OPV produced by a manufacturer, who has since been severely penalised.


Since WPV Type 2 has been declared as eradicated, and had not been detected since 1999, India has shifted from Trivalent Oral Polio Vaccine, tOPV, (containing Sabin Types 1, 2 and 3) to Bivalent Oral Polio Vaccine, bOPV (containing only Sabin Types 1 and 3). The reason for this is, with WPV Type 2 transmission already having been successfully interrupted, the only type 2 poliovirus which still causes paralysis, on very rare occasions, is the Sabin Type 2 serotype component in Trivalent OPV.


What is the significance of this discovery?


Since the switch from Trivalent OPV to Bivalent OPV in India in April 2016, all children who have been vaccinated exclusively with OPV from that date onwards, do not have immunity against Polio Virus Type 2.


The strain discovered in the stool sample was Polio Vaccine Virus (Sabin) Type 2, which is a live attenuated (has lost the capacity to cause disease) version of Wild Polio Virus Type 2. This strain per se is harmless, and the only danger is the small chance of it mutating and regaining back its virulence (the capacity to cause disease).


Who are the children at risk?


The contaminated batches of Bivalent OPV were used in the government immunisation programs (this OPV manufacturer does not supply to the private doctors) of the states of Uttar Pradesh, Maharashtra and Telangana. The government has immediately discontinued the use of the vaccine in these areas, and stepped up surveillance and mop up immunisation.


Which are the children who are not at risk?


Any child who has received two doses, or at least one dose of the Injectable Polio Vaccine (IPV), which contains all the three strains of the polio virus, will have immunity against Polio Virus Type 2. IPV is, and has been since 2016, routinely administered in government hospitals and PHCs in two doses at 6 and 14 weeks. In the private sector, IPV is no longer available as a standalone vaccine (Imovax Polio, Polprotec), and is presently available only as a component of a combination vaccine, Hexaxim and Infanrix Hexa (DTaP + IPV + HepB + Hib), and EasySix (DTwP + IPV + HepB + Hib). Any child who has received any of the above vaccines will be protected from Type 2 polio virus.


What do we do now?


• All children from the involved states who have received the contaminated batch will be given IPV, if they have not received it already


• All children born after April 2016, who have received only OPV, should take at least one dose of IPV from a nearby Government facility as early as possible.


• All children who have taken at least two doses of IPV, need not do anything more. They should continue to take other vaccinations as recommended by their doctor, and also take part in the Pulse Polio immunisation programs to ensure that our country remains free of Polio.


• Children less than 6 weeks, who have not received any vaccine yet, should get at least 2 doses of IPV, from either the government or the private sector doctors, in addition to the Oral Polio Vaccine (OPV).  The administration of OPV should not, on any account, be discontinued or defered because of this unfortunate incident.

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