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Letters to the Editor Indian Pediatrics 2000;37: 1395-1400 |
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Polio Eradication Strategy: Need for Re-appraisal |
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Dr. Yash Paul needs to be aware of the different classification schemes of acute flaccid paralysis (AFP) and of the fact that India is using WHO’s Virological Classifica-tion Scheme to classify AFP cases from January 2000. This classification scheme has greater accuracy than the clinical Classifica-tion Scheme that was being used in 1999. It is not a fact that compatible cases are not considered polio cases. On the contrary all compatible cases are taken as polio cases and are line listed. Dr. Yash Paul has further confused the issue when he tries to correlate the administration of OPV after the onset of paralysis. It is to be noted that in response to every reported case of AFP, an ‘Outbreak Response Immunization’ (ORI) is conducted in the area, but only after completing stool collection. More than 50% of cases shown in Table II of his letter had received OPV more than 2 weeks later than the onset of paralysis and this cannot interfere with the stool culture for polioviruses. There is no data mentioned about the two cases that had expired. As the children had died on the very same day, it would be extremely unscientific to correlate any of these deaths with OPV administration after the onset of paralysis. The risk of vaccine associated paralytic poliomyelitis (VAPP) has been evaluated and is reported to be 1 case per 4 million doses administered, overall(4). The risk of VAPP for any individual is greatest with the first dose (1 case per 2 million doses) and decreases with subsequent doses (1 case per 12 million doses). The decision by the United States to switch from OPV to IPV was taken only after the country had been rid of polio for 20 years. The intent was to eliminate the risk of VAPP (8-9 cases per year), which it has accomp-lished at the cost of approximately $3 million per case of VAPP averted. In their policy statement, the US Centers for Disease Control and Prevention (CDC) reiterated that OPV continues to be the vaccine of choice in areas such as India where polio continues to be endemic. Dr. Yash Paul’s recommendation for raising the age of vaccination from 5 to 12 years is based on his observation of only 56 cases. Out of the 56 cases mentioned, 17 subjects were above the age of 5 but all of them were clinically confirmed cases. All the 5 virus positive polio cases were under the age of 5 years. In fact, all virus positive polio cases of Rajasthan in 1999 (total 18) were under 5 years of age. Moreover, 96% of all virus positive polio cases in 1999 in India were under the age of 5 years, the median age being 17 months. Even in the year 2000 (up to week 34), 92% of all virus positive polio cases and compatible cases in India are under 5 years of age (Kaushik Banerjee, Personal Communication). The ultimate success of polio eradication in India will depend on the continued efforts of mothers, the 2.7 million health workers, teachers, Rotarians, and other volunteers who selflessly work to assure that the vaccine reaches every child less than five years of age. The Indian Academy of Pediatrics plays a lead role in advocacy and stands strongly behind the strategy adopted by Government of India to eradicate polio. In the end, global eradication will eliminate the need for any vaccine against polio, forever. Naveen Thacker,
My response to the various issues raised is as below: Classification of AFP Cases It is a fact that WHO’s Virological Classification Scheme is more accurate as compared to the Clinical Classification Scheme which was being followed upto 1999. The limitation of virological confirmation is the rate of virus detection. Viruses usually can be found in the feces from 72 hours upto 6 or more weeks after infection, with the highest probability during the first two weeks. The dates of onset of paralysis, collection of 1st and 2nd stool samples and delivery to the assigned laboratory are given in Table I.
It can be seen that many stool samples were collected after lapse of more than four weeks, so chances of virus detection would not be optimal. Similarly, for the child at serial number 3, stool samples were collected on 18th and 19th January, but the samples reached the assigned laboratory on 24th March. Out of 56 cases, stool samples had been collected in 27 cases only. I would re-iterate that if we depend only on wild polio virus detection in the stool sample of AFP cases to label a case of paralytic polio, then we may miss many cases. OPV Administered After Onset of Paralysis Dr. Thacker has stated: "Dr. Yash Paul has further confused the issue when he tries to correlate the administration of OPV after onset of paralysis. It is to be noted that in response to every reported case of AFP an ‘Outbreak Response Immunization’ (ORI) is conducted in the area, but only after complet-ing stool collection". I want to make it clear that I had mentioned about the polio cases who had received OPV dose after onset of paralytic polio, I had not discussed ORI, so there should be no confusion regarding this point. The child will not derive any benefit from the OPV dose administered at this stage, the only benefit that can arise is an increase in the number of OPV doses administered during the PPI rounds without any benefit to the child. On the other hand it may result in vaccine polio virus being found in feces of AFP cases. Dr. Thacker has further stated: "More than 50% of cases shown in Table II (of my letter) had received OPV more than 2 weeks later than the onset of paralysis and this can not interfere with stool culture for polio-viruses". Out of 51 stool samples collected in the report, 41 samples were collected after an interval of more than two weeks of onset of paralysis.
Dr. Thacker has further stated: "As the children had died on the very same day, it would be extremely unscientific to correlate any of these deaths with OPV administration after onset of paralysis". I had not even indirectly or obliquely stated OPV to be related with the death of the children. Deaths occurring in paralytic polio cases after OPV administration have confirmed my earlier apprehension. "An ill child administered any vaccine if later develops complication of the disease, the vaccine may be blamed for the complications or even death"(1). It has been observed after every PPI round that deaths are reported by media and are erroneously assigned to the polio vaccine. Even after the 24th September 2000 round of PPI many such reports from West Bengal appeared in the media. I had stated this so as to be cautious regarding this aspect, as it was bound to create a negative impact. Vaccine Associated Paralytic Poliomyelitis Dr. Thackder has stated: "The risk of VAPP for any individual is greater with the first dose (1 case per 2 million doses) and decreases with subsequent dose (1 case per 12 million doses)". According to the IAP working definition of VAPP, a case of paralytic polio should be labelled as VAPP if paralysis develops within 7-30 days of administration of OPV but no wild polio virus is detected in the stool samples and/or vaccine polio virus has been detected in the stool sample but OPV has not been administered after onset of paralysis and before collection of stool sample. The report of 56 cases from Rajasthan that I had referred to had seven cases of VAPP according to date of OPV administration and date of onset of paralysis. The data are presented in Table II. In this series of seven cases, two children had received one dose each, while other five children had received 5 to 10 doses each. Thus the risk of VAPP with subsequent dose is very much there; in fact it becomes a case of Vaccine Failure followed by VAPP. Age Limit for OPV Administration It is right that I had based my observations on 56 cases from Rajasthan mentioned in that report. If paralytic polio cases in children above 5 years of age have not been reported from other places then there is no need to raise the age limit for OPV administration. Vaccine Failure Dr. Thacker has not commented on incidence of vaccine failure. May be cases of vaccine failure have not been observed in other parts of the country. I would like to make a correction regarding the number of the children who developed polio and died. In my letter I had mentioned the number of such children as eight. I was wrong. I had counted the columns where it was mentioned ‘child expired before collection of stool’s, etc. On closer scrutiny I found that number of children who had developed polio and died was in fact 24 i.e., 40% children had died. It was mentioned as code number 4 under ‘Follow Up Results’. If required, I can provide details for all the 24 children who died. Twelve white tigres died in Nandan Kanan resort recently and the matter was raised in both houses of the Parliament. In Rajasthan twenty four children died after developing polio, between 1st January and 31st July 1999, some of whom had been administered a high number of OPV doses; very few are even aware of these facts. Efficacy of OPV Dr. Thacker has stated: "That the choice of OPV was correct one has been borne out by the fact that the number of polio cases in India has dropped from an estimated 32630 in 1995, before the Pulse Polio Program began; to just 1126 cases in 1999 with 88% of these cases confined to just 4 states (Uttar Pradesh, Bihar, Delhi, West Bengal)". I am presenting here year-wise breakup of number of polio cases during the nineties: 10408 in 1990, 8670 in 1991, 9390 in 1992, 7576 in 1993, 4791 in 1994, 3263 in 1995, 1005 in 1996, 2274 in 1997, 4322 in 1998 and 1126 in 1999. It can be seen that the fall in number of polio cases is not regular, it had moved up and down in different years; both before and after Pulse Polio Campaign. A similar pattern was observed during the eighties also. The number of polio cases in 1995 was 3263 and not 32630 as mentioned by Dr. Thacker. OPV has brought down the number of polio cases which varied from 14000 to 30000 cases per year during the eighties to 1126 cases in 1999. If we continue to administer OPV even after elimination of wild polio virus, then we will have VAPP cases only. It has already happened in Indonesia and Thailand, where wild polio virus is not being found in the stool samples of polio cases, only vaccine polio virus is being detected(2). Because of financial and logistic compulsions we had to depend in the past exclusively on OPV for polio eradication. IPV should now be introduced in a phased manner:
My humble suggestion is that IAP should constitute a task force for an in-depth study of the issues that I had raised, and also to look if these were local phenomena confined to Rajasthan only or were occurring elsewhere also. Dr. Thacker has stated: "The observa-tions made by Dr. Yash Paul in his letter and the perceived interpretations are unfortunate because these come at a critical time when India is moving towards the final stages of polio eradication. Dr. Thacker is unhappy on two counts: (i) the contents of my letter, and (ii) timing of its publication. Somehow, Dr. Thacker had drawn many inferences on his own, some were not right while other were wrong. I would like to cite one example. Dr. Thacker has stated: "There is no data mentioned about the two cases that had expired. As the children had died on the very same day, it would be extremely unscientific to correlate any of these deaths with OPV administration after the onset of paralysis". Data provided by me contained all the details–age, number of doses received, date of onset of paralysis, date of OPV adminis-tered, duration of illness and the home district. IDCODE number of these two children were RJDTP99001 and RJKTA99004. In Table I they were mentioned at serial numbers 5 and 6, and in Table IV at serial numbers 2 and 5, respectively. Duration of illness before death was 6 days and 3 days, respectively (mentioned in Table IV). I am amazed that Dr. Thacker arrived at the conclusion that both children died on the ‘very same day’. Regarding the timing of its publication, the incidence of wild polio virus has come down, so it is the right time to change over to IPV, and IPV is being made available in India soon. Yash Paul,
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