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Images in Clinical Practice Indian Pediatrics 2000;37: 1025-1026 |
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Measles or Chicken Pox and Post-Exposure Rabies Immunization |
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Dr. Jacob John has stated "If a child falls ill with any of them (fever, diarrhea, dysentery, etc.) during the course of rabies immunization after bite from a rabid animal, I would continue the doses as per schedule". Recently, this question arose in a child who developed chicken pox rash during post exposure immunization and the course went uninterrupted(1). Rabies vaccine merits special considera-tion. There is no option, because the choice is between certain death due to rabies and the rare probable risk of adverse reaction. Rabies vaccine is an inactivated vaccine and not a live attenuated vaccine. Because of chicken pox or measles infection, or Measles or MMR vaccine administered less than 6 weeks earlier, the antibody production may be slightly less, so either additional passive immunization and/or the first dose or the next first dose after immuno-suppression should be doubled. The two doses administered same day should be given at two separate sites. There is absolutely no reason to consider withholding of post-exposure rabies immunization during any illness, not even during the polio out-break or epidemic, conversely additional dose merits consideration. Yash Pal,
Dr. Yash Paul suggests that the post-exposure rabies immunization should be modified in children who have had measles or chickenpox, or had been given measles or varicella vaccine, within 6 weeks before the rabies exposure. Specially, he suggests "either additional passive immunization and/or the first dose or the next first dose (in case of the illness appearing during the course of rabies immunization) should be doubled". He would give the two doses the same day, but at separate sites. I do not believe that there is any need to modify the rabies immunization protocol in children who have had recent measles, chickenpox or the respective immunizations. The current recommendation on passive immunization is to give it in all cases of exposure to a rabid animal. When rabies in the biting animal is suspected on circumstantial evidence, the animal is taken to be rabid. Even when a biting animal is not suspected of rabies at the time of biting, but the animal is under observation, passive immunization is recommended for bites on face, head, neck, hands and genital area. Multiple bites or severe bites with extensive tissue damage should also merit passive immunization. If the animal is not available for observation, we err on the side of assuming that it had been infected. These recommendations are sufficient even for children who have had measles, chickenpox or their vaccines within 6 weeks. Obviously, this is more a matter of opinion than evidence-based. The rabies prophylaxis course is meant to induce early antibody response, high response and sustained antibody levels. It is for this reason that we give a rather liberal dose schedule on days 0, 3, 7, 14 and 30. In children given passive immunization, a dose of vaccine should be given on day 90. The mild immuno-suppression of measles, or the even milder immunosuppression of measles vaccination is unlikely to reduce the immune response level to the rabies vaccine given in this sequence. Passive immunization itself is inhibitory to normal immune response but we do not double the dose of vaccine at any point of time. It is very unlikely that the immune suppression of measles, varicella or their vaccines would be more than that of specific reduction of antibody levels due to passive immunization itself. Such blunting (not necessarily total aborgation) occurs with natural passive immunization by maternal antibody against hepatitis A vaccine or injectable poliovaccine. Such effect on hepatitis B vaccine is much less, rather like the case of rabies vaccine. On the other hand, in the case of live vaccines (measles, mumps, rubella or varicella vaccines) maternal antibody can completely suppress an immune response. If the analogy of antibody inhibition by passive immunization is taken as a model, then at the most one could consider giving a dose of rabies vaccine on day 90 for those children who have had measles or measles vaccine within 4 weeks. In my personal opinion this additional dose is not necessary, except in children given passive immunization. I do not think that this is an issue with varicella or its vaccine. This is a more rational approach than arbitrarily giving passive immunization where it is not needed or doubling the dose unnecessarily. T. Jacob John, |
