INDIAN PEDIATRICS VOLUME 34-SEPTEMBER 1997

Immunization Dialogue

Should We Revise the Primary have two competing demands. Increasing Schedule the intervals between the first and second and second and third doses to two months On page 17 of the "IAP Guide Book on (or 8 weeks) instead of one month (or 4 Immunization" (Dec. 1996) courtesy Smith- weeks) would certainly improve antibody Kline Beecham, it is stated that "Between 2 levels in the case of most non-replicating doses of the same (DPT and OPV), such as , a minimum interval of 4 weeks should be and injectable vaccine. For observed. Increasing the interval between vaccine, the manufacturers recommend doses to 2 or 3 months actually improves intervals of 1 month between the first and antibody levels. The maximum allowed in- second doses and 5 months between the terval between the first and second dose of second and third doses, for obtaining high a non-live (DPT) vaccine is arbitrarily one antibody titers. year. Between 2nd and 3rd dose also, the minimum interval is 4 weeks, the optimum On the other hand, 2 or 3 doses of vac- 3 to 6 months, and the maximum again cines given in quicker succession provides arbitrarily five years." protective immunity much sooner. When interval between doses is reduced, the One would like to know that in the light seroconversion (development of detectable of the above statement, why the Time Table antibody level) would be faster, but the for DPT along with OPV during the first level (titer) achieved would be lower. year has been changed from 2 months, 4 Hence, the number of doses has to be in- months and 6 months to 6 weeks, 10 weeks creased for improving antibody levels. This and 14 weeks (page 28)? Although this may principle is used in rapid immunization lead to early completion of the primary with cell culture after expo- immunization for OPV and DPT, but may sure, when doses are given on days 0, 3, 7, result in partially immunized children who 14 and 30. Japanese encephalitis (JE) vac- may get the disease(s) against which they cine is often needed at short notice, either have been sub-optimally immunised. due to impending epidemic or for travel to Yash Paul, a JE endemic area. Here, the mouse-brain A-D-7, Devi Marg, grown may be given Bani Park, on days 0, 7 and 30, or even on days 0, 7 Jaipur 302 016. and 14, for rapid response. Subsequent booster one year or more later provides Reply longer term protection. It is true that in the USA the recom- I am very pleased to know that the IAP mended schedule of primary immuniza- Guidebook on Immunization, written care- tion with DPT is 3 doses at 2, 4 and 6 fully, is also being read carefully. months of age. The WHO EPI schedule, af- ter which the India EPI schedule is fashion- The intervals between doses of ed, calls for earlier immunization at 6, 10

839 IMMUNIZATION DIALOGUE and 14 weeks. Although the antibody 'partially' or 'sub-optimally' immunized levels may be somewhat lower, with the against , Pertussis and during the second year of life , as feared by Dr. Yash Paul. excellent levels would be reached under Regarding OPV, some 60-70% of infants both schedules. IAP has adopted this would be fully protected with 3 doses schedule for several pragmatic reasons. In given at 4 or 8 weeks intervals. To cover general, early start and shorter intervals are the gap in immunity additional doses are better complied with by mothers. In addi- essential; increasing the interval would tion, DPT given under the umbrella of ma- not achieve this. In summary, there is no ternal poliovirus antibody cover reduces need to revise the primary immunization the risk of provocation poliomyelitis. In- schedule at the present time. deed, IAP was the first agency calling for the revision of the earlier EPI schedule (2-3- T. Jacob John, 4 months) to the 6-10-14 week schedule, Chairman, way back in 1980, following an IAP Work- IAP Committee on Immunization and Emeritus Professor, shop at Vellore. Department of Clinical Virology, There is no evidence to suggest that the Christian Medical College, 6-10-14 week schedule leaves infants only Vellore 632 004, Tamil Nadu.

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