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Immunization Dialogue Indian Pediatrics 2000;37: 1387 The
views expressed by Prof. T. Jacob John in this section are personal
in nature and should not be construed as the official stand of the
Indian Academy of Pediatrics. –Editor-in-Chief |
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Testing Vaccine Potency |
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S. Nagabhushana, The potency of all vaccines is measured before release, by the Government of India Vaccine Quality Control and Testing Laboratory at the Central Research Institute, Kasauli. For all vaccines, post-vaccination follow up of children is the simplest way of knowing about potency. In the absence of the target disease occurring after immunization we can assume that the potency has been satisfactory. If disease occurs after immuniza-tion, then the potency needs to be checked. The exception is OPV, since its efficacy is low after 3 doses. The efficacy of pertussis vaccine also may be in the order of some 80% and a few cases of pertussis, especially mild cases, may not be a cause for worry about potency. For BCG the skin reaction itself is a good guide of potency. Potency tests are bioassays. Most such assays are expensive. Each vaccine manu-facturing unit is the best place to get the potency verified. For inexpensive vaccines like BCG and DPT, when potency is in doubt, it is quite reasonable to discard the stock and procure a fresh batch. For more expensive vaccines (and for any vaccine, for that matter), one easy method of assessing potency is to measure the antibody response of a few vaccinees. The potency of OPV is being monitored regularly by the several national polio laboratories. Since the vaccine vial monitor is now attached to every vial, there is no need to measure the potency; its potency had already been checked at Kasauli and thereafter the potency is maintained by the low temperature of storage and transportation. T. Jacob John, |
