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Adverse Events Associated with Childhood Vaccines: Evidence Bearing on Causality
tive risk is available. Estimates from the studies described above range from 1 per 20,000 to 1 per 1 million doses distributed.
The evidence is inadequate to accept or reject a causal relation between mumps vaccine and anaphylaxis.
Most anaphylactic reactions occur in individuals who have no known risk factors for severe reactions to these vaccines; thus, no special precautions can be taken. Patients who have demonstrated severe systemic reactions to egg protein or neomycin may be at increased risk of anaphylaxis following receipt of measles or mumps vaccines, and guidelines for immunizing such patients have been provided by the Committee on Infectious Diseases of the American Academy of Pediatrics (1991). Patients with allergies to other antigens, including chickens and feathers, are not at increased risk of severe allergic reactions to these vaccines.
A detailed discussion of the evidence regarding death following immunization can be found in Chapter 10. Only the causality argument and conclusions follow. See Chapter 10 for details.
The data relating death and measles or mumps vaccine are from case reports and case series. The largest series comes from India, but toxic shock syndrome caused by the unhygienic conditions involved in the immunization program was the apparent cause of death reported for eight of nine patients. Evidence based on RNA sequencing techniques has linked measles vaccine and measles infection to subsequent death in some severely immunocompromised children. In contrast, studies of the immunogenic response to measles vaccine in children infected with human immunodeficiency virus, which causes acquired immune deficiency syndrome, have not recorded any deaths from measles infection.
The evidence favors the acceptance of a causal relation between measles vaccine and anaphylaxis. The evidence establishes a causal relation between MMR and thrombocytopenia and anaphylaxis. Anaphylaxis and thrombocytopenia can be fatal. Although there is no direct evidence of death as a consequence of measles vaccine-related anaphylaxis or of MMR-related thrombocytopenia or anaphylaxis, in the committee's judgment measles vaccine could cause fatal anaphylaxis and MMR could cause fatal