POLIO - CURRENT STATUS - ROLE OF IPV
Dr. Atul K. Agarwal*, Ashvir Batra**
(Bareilly), National Co-Convenor - Polio Eradication Committee, IAP*, (Bareilly), National Co-Convenor - Polio Eradication Committee, IAP.**
POLIO: CURRENT STATUS - ROLE OF IPV
31st May, 2007, Polio tally: 55 (P1: 31; P3: 24). The year which has just passed was an epidemic year like we had in 1998 & 2000. So, the more apt will be to compare this year with the years following the outbreaks. In the year 1999, the figure was 116 and in 2003 it was 88, while in the year 2007 it is 55. In a span of these eight years, the post-epidemic year is showing a constant improvement, but at a very slow pace. The only heartening news is that out of 55 cases reported this year, only 31 cases are of P1 virus, which is known for its extensive travel habits. Out of the remaining 24 cases of P3 virus, majority are in Rohilkhand region of UP, confined to only 5 districts only. This P3 virus is easier to be dealt with as compared to P1, which travels across the length and breadth of the country in a hopping manner. For the last many weeks, it is only the P3 cases which are being reported. This means that the immune response is much stronger after the natural infection as compared to the repeated rounds of OPV. This "fact" forces us to re-evaluate our strategy of having multiple rounds of mOPV1 in high risk districts of UP and Bihar. We have to wait and watch for the coming rainy season to reach to any further conclusion. The challenge at the moment is to decide as to how we can effectively contain P3 without losing grip over PP1 in Western UP. Either we will have to switch over to bivalent (P1 + P3) vaccine or more extensive rounds of monovalent P3 to break its transmission (So far only 01 round has been done in a few districts of UP). The Epidemiology of Bihar is different from UP, where more number of cases is above 2 years of age. So, we will have to plan different strategies for UP and Bihar.

The most recent study of Jay Wenger et al published online (April, 2007) also shows that the protective efficacy of MOPV is around 30% (90% CI 19-41) per dose against Type 1 paralytic disease as compared to 11% (7-14) for the trivalent oral vaccine. 76-82% of children aged 0-23 years were estimated to be protected by vaccination against Type 1 polio virus at the end of 2006, compared to 59% at the end of 2004, before the introduction of M OPPV1. But still, we are having 1825% children who are "unprotected"; which is the most alarming subject of concern. At this juncture, there is a need for ourselves to prepare for the future available injection vaccine which is far more efficacious to bridge this gap.
INJECTABLE POLIO VACCINE (IPV)
It produces excellent humoral, local pharyngeal and possibly intestinal immunity too. It is a very safe vaccine with a proven efficacy of 95%. It not only gives excellent individual protection, but also reduces the chances of VAPP (though not common in India at present). This is a very promising vaccine in a scenario where in spite of significant reduction in immunity gap from 2003 to 2007, the WPV transmission is still in full force in endemic areas of UP and Bihar. India being a poor developing country where the majority lives below the poverty level, the price factor might be a hindrance till indigenous production starts here and the price is brought down. IAP COI recommends it to be a vaccine which can be given after one-on-one discussion with parents in the population with affordability. This vaccine is at present, only for the classes, and unfortunately, not for the masses. We will have to continue OPV administration as per EPI & PPI schedules till further change in policy.


Schedule I Schedule II Schedule III Schedule IV Schedule V
Birth OPV OPV OPV
2 doses after the age of 2 months to 2 years at a gap of 2 months in fully vaccinated (OPV) child
 
6 weeks OPV IPV OPV IPV
8 IPV      
10 OPV IPV OPV+IPV IPV
14 OPV IPV OPV+IPV IPV
16 IPV      
18 months IPV IPV OPV+IPV IPV (No OPV)
OPV to be given on all NID & SNIDs as per plans from time to time.


IAP PEC & IAP COI strongly recommend that since IPV will be required in post-eradication phase of polio. GOI and IAP members should gear up to include this vaccine (IPV) in the National Schedule.
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