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Indian Pediatrics 2005; 42:1007

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WHO has shelved the controversy on the use of thiomersal as preservative in multi dose vaccine formulation vials. Being an ethyl mercury, it does not produce any neurotoxcity unlike methyl mercury. With 25 mcg for each vaccine administration (much less in combination formulation multi dose vials), the cumulative effect on neuro-toxicity, once feared is no more a concern. Therefore, many countries in the world use thiomersal preserved vaccine formulation in their routine National Immunization Program.

Without going into the pros and cons of 6,10,14 weeks and 8,16,24 weeks, it is worth while following the latest WHO schedule for DTwP and HB Vaccine which is highly immunogenic and has established high field efficacy since 1975 and 2000 respectively. No doubt, increasing interval between the 3 doses of the same vaccine, enhances the immunogenicity, GMT, etc. However, the minimum protective antibody level achieved through wider coverage at short interval with excellent field efficacy, have resulted in successful elimination/eradication of the targeted diseases in countries world over using the WHO schedule.

A. Parthasarathy,
42/166, ‘Brindavan’ Park Road,
Anna Nagar, Western Extension,
Chennai 600 011, India.

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