Thrombocytopenia is a decrease in the number Of platelets that are involved in blood clotting. Thrombocytopenia can stem from the failure of platelet production, a shortened platelet life span, or an abnormal distribution of platelets within the body. In most cases, thrombocytopenia in children is mild and transient, and it is often discovered only incidentally when a complete blood count is performed. Severe thrombocytopenia associated with spontaneous bleeding, including bleeding into the skin, is called thrombocytopenic purpura. No population-based incidence rates for either condition were identified.

The committee was asked to evaluate the data regarding a possible causal relation between IPV only and anaphylaxis and thrombocytopenia.

Evidence for Association

There are no published reports of anaphylaxis or thrombocytopenic purpura associated with IPV.

Conclusion

There is no evidence bearing on a causal relation between IPV and anaphylaxis.

There is no evidence bearing on a causal relation between IPV and thrombocytopenia.

DEATH

A detailed discussion of the evidence regarding death following immunization can be found in Chapter 10. Only the causality argument and conclusion follow. See Chapter 10 for details.

Causality Argument

The evidence favors acceptance of a causal relation between OPV and GBS. The evidence establishes a causal relation between OPV and paralytic poliomyelitis in recipients or contacts. GBS and paralytic poliomyelitis can be fatal. Although there is no direct evidence of death as a consequence of OPV-induced GBS, in the committee's judgment OPV could cause fatal GBS. There are data regarding death from vaccine-strain poliovirus infection; the data derive primarily from immunocompromised individuals. There is no evidence or reason to believe that the case fatality rate for GBS or vaccine-associated poliovirus infection (including that resulting in paralytic poliomyelitis) is greater than that for these adverse events associated with any other cause.

The possible causal relation between polio vaccines and sudden infant



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