Dear Sir
Good day.
I have faced one question regarding NIDs, which is: if one of the governorates or provinces in any country achieves a routine immunization coverage rate of more than 95%, is there need to proceed with NIDs? This question was raised in Iraq.
My first response: I reminded him (of our experience) with the Polio Eradication Strategy. Then he insisted that he achieved routine coverage of more than 95% and AFP surveillance. Then I clarified that it depended on national strategies and that it would depend on how long the coverage rate has been more than 95% and what is the population density of the governorate and if it is isolated geographically from other governorates— all these 3 factors affect the decision to stop PNIDs in any governorate and this is a decision to be taken at the national not the provisional level.
Regards
Riadh
M B CH B DCM
+964 780 1011077
+964 770 2763418
Riadh,
I totally agree with you on the clarification.The aim of Polio Eradication Strategy is to reach all the children under five years. By doing so we give a chance to those children who were not reached during the Routine Immunization. Children who were not reached during RI are obvious unvaccinated. This group accumulates every year. Depending on RI target population, 5% of children who were unvaccinated in five years can be enough to create outbreak. Example of countries with target population in some of provinces of 500,000 this means 25,000 children are unvaccinated per year. For five years, then you have 125,000 children. I am not an expert on sero-conversion of OPV but obviously there is a certain % who don’t seroconvert and we need to reach them.
I agree that the province maintain the coverage of 95% for longer period and have moderate target population, then they will have a longer period of honey moon but at certain point they need to do NIDs to reach all unvaccinated children during RI and missed children during the previous NIDs.
Chris
It is good to pose such queries and questions which initiate debates.
We have to recall the strategies of polio eradication and the objectives and aims of administring OPV in 2 different strategies, routine doses and doses through SIAs. The OPV is the same and the response is the same but the objectives are different. The routine immunization targets individual protection through serum immunity which is life long. The SIA doses aim at intestinal immunity, where the objective is community protection though the child also benefits in raising his/her serum immunity if the routine doses have not achieved the required level. The other example can be given of IPV which also raises serum immunity and is advised for individual protection but not the community protection as intestinal immunity is not developed. As we know that the the receptors at intestinal epithelim of human being is the only major place where replication of poliovirus takes place, both wild and vaccine. The SIA doses are given at 4-6 weeks interval to block the recepters and not allow the poliovirus to replicate so that it can be eradicated easily as the survival outside the human intestine is quite limited (weeks). The importance of high routine coverage cannot be denied as it supports the eradication and makes it possible through few rounds and good example is given of China where high routine coverage supported eradication efforts and few rounds made it possible to eradicate. The countries which continue with NIDs or SIAs are either endemic or at risk of importation and are supposed to continue with a few rounds of SIAs to keep the immune profile high. The immune children in countries with high routine coverage and high level of immunity profile will give Herd immunity to the children immunized and there will be the minimum chances of establishing poliovirus circulation. RegardsDr. Hassan KhanMBBS, M.Sc
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