Poliovirus vaccine policy: another perspective

Article Abstract:

Two types of vaccines are used to prevent poliomyelitis, a live virus vaccine called trivalent oral poliovirus vaccine (TOPV) and a killed virus vaccine called inactivated poliovirus vaccine (IPV). A new, more protective vaccine, enhanced potency inactivated polio vaccine (E-IPV), has recently been developed. This should be available in a few years in combination with three other vaccines protecting children from diphtheria, tetanus and pertussis (DPT); the combined vaccine will carry the designation DPT-E-IPV. Polio virus can be transmitted by the actual vaccine or by contact with a wild polio virus. The United States originally used the IPV until greater disease protection was found to result from oral live virus vaccine, which was being used in Europe. Most cases of polio are found in unvaccinated children, as, for example, a group of Amish children in 1979. There have been some isolated cases of polio contracted from doses of oral live virus vaccine, affecting either the vaccine recipients or their contacts. The current immunization program has proved effective, as evidenced by the lack of disease caused by imported viruses. Only two cases of vaccine-associated polio were reported in 1988. Fewer than 10 percent of the cases of oral vaccine-related polio have been reported in patients that have not yet been identified with immunosuppressive disease. Although reports from Europe have hailed the use of IPV, outbreaks have been described in Finland, the Netherlands and Israel. A group of IPV-vaccinated children were responsible for transmission of the wild virus, raising questions about the intestinal polio virus protection offered by the oral live virus vaccine but not by the IPV vaccine. In Israel, the new enhanced IPV was used and in 1988, 12 cases of polio were reported in children, mostly over the age of 17. The vaccinated children, although not themselves infected, were thought to have shed the wild virus from the intestinal tract to unprotected teenagers. The Institute of Medicine's current policy will be to recommend that the new E-IPV vaccine replace the old IPV vaccine. When the combined formula, DPT-E-IPV, becomes available, it is to be given in two or more doses, followed by oral (live virus) vaccine at 18 months and upon entering school. Furthermore, there are many issues surrounding the safety of the current pertussis vaccine. Until the problems of clinic versus private physician immunization schedules are resolved, a change in policy, regarding the E-IPV combined with OPV vaccine, is premature. (Consumer Summary produced by Reliance Medical Information, Inc.)

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Why wait for DPT-E-IPV?

Article Abstract:

The Institute of Medicine has appointed a panel of experts to review policy options regarding vaccination against poliomyelitis, a viral disease causing paralysis. Two types of vaccines are currently in use, a live virus vaccine called trivalent oral poliovirus vaccine (TOPV) and a killed virus vaccine called inactivated poliovirus vaccine (IPV). However, a new, more protective vaccine, enhanced potency inactivated polio vaccine (E-IPV), has recently been developed, and should be available in a few years, in combination with three other vaccines protecting children from diphtheria, tetanus and pertussis (DPT). The combination will carry the designation DPT-E-IPV. Polio virus can be transmitted by the actual vaccine or by contact with a wild polio virus. Although vaccination with TOPV vaccine can cause paralysis (because it is a live virus vaccine), it has, up until now, been the preferred formula. The Institute of Medicine reports that its policy will be to recommend that the new E-IPV vaccine replace the old IPV vaccine. When the combined formula DPT-E-IPV becomes available, it should be given in two or more doses, followed by the oral (live virus) vaccine at 18 months, and again when the child is ready to enter school. The policy decision was based on the fact that the killed virus vaccine is not as effective as the oral live vaccination for destroying the virus in the intestines. Therefore, producing initial immunity with the E-IPV vaccine before the live virus is given would effect a reduction in the incidence of paralysis. The panel was concerned that using E-IPV vaccine alone before the combined vaccine was available would create problems controlling immunization schedules, because two or three more shots would be needed for complete immunity. The ethics of the panel's decision to wait for the new combined vaccine licencing are arguable. If parents and physicians agree on a combined E-IPV and OPV schedule, the cost and discomfort of the combined schedule far outweighs the risk of paralysis, even though it occurs rarely. (Consumer Summary produced by Reliance Medical Information, Inc.)

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The humoral immune response to type 1 oral poliovirus vaccine in children previously immunized with enhanced potency inactivated poliovirus vaccine or live oral poliovirus vaccine

Article Abstract:

There are two types of polio vaccines that are currently used, the live attenuated oral poliovirus vaccine (OPV) and the inactivated poliovirus vaccine (IPV); the debate continues as to which type is superior. In rare instances, the live vaccine causes paralytic polio. This problem, along with the development of an enhanced potency IPV (epIPV), has caused the medical community to look favorably on the inactivated vaccine. One treatment alternative is to give the epIPV vaccine initially, and use the OPV vaccine as a booster. A study was conducted which compared the effects of a booster dose of OPV vaccine in two groups of children. One group had previously been given three doses of epIPV vaccine, and the other group was given three previous doses of OPV. Prior to administration of the booster, the children receiving the epIPV vaccine had an antibody count of 11.1, compared with a count of 2.2 in the OPV recipients. Following the booster, the antibody count in the epIPV group soared to 35.3 compared with 5.1 in the OPV group. The effect of the booster was significantly greater in the epIPV group. The lower OPV booster effect in children who had previously received OPV vaccine is thought to be caused by an induced immunity to the OPV vaccine. However, an important advantage of the OPV vaccine is its proven ability to provide immunity against all three polioviruses. Whether or not a sequential administration of the epIPV vaccine in conjunction with the OPV booster will provide equivalent immunity needs to be determined. (Consumer Summary produced by Reliance Medical Information, Inc.)

Physiological aspects

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