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Adverse Events Associated with Childhood Vaccines: Evidence Bearing on Causality
Early Reports of Vaccine-Associated Poliomyelitis, Published Before 1970
Chang et al., 1966
One 7-yr-old with hypogammaglobulinemia
Morse et al.,. 1966
One adult (mother of infant)
Stolley et al., 1968
One 16-mo-old boy
Swanson et al., 1967
One 29-yr-old father of 2-yr-old recipient
Henderson et al., 1964
57 vaccine-associated cases (1962-1964; may include 3 contact cases)
Balduzzi and Glasgow, 1967
One 5-yr-old boy
Cesario et al., 1969
Evidence for Association
OPV consists of live attenuated viruses that multiply in the intestinal tract and that can revert to a more virulent form, causing disease. A vaccine recipient excretes live virus for several weeks, and recipients or contacts may become infected with the virus.
Case Reports, Case Series, and Uncontrolled Observational Studies
Since the 1960s there have been about 100 studies reporting individual cases, case series, and national surveillances of vaccine-associated cases of paralytic poliomyelitis. Case definitions have been well developed by the CDC and the World Health Organization (WHO); a case of vaccine-associated paralytic poliomyelitis is said to occur in recipients if the onset of the disease begins 7-30 days postvaccination and is said to occur in contacts of vaccine recipients if the onset of the disease begins 7-60 days after a recipient's vaccination. Laboratory tests can identify the strain of the infecting virus as a wild-type or vaccine strain of poliovirus. The cases described above in the section History of Suspected Association are typical of those that followed in the 1970s and 1980s.
WHO and CDC have used standard definitions of cases of paralytic poliomyelitis for almost 30 years, and many nations have implemented polio surveillance systems to monitor their polio immunization programs. Table 7-2 summarizes national data from the United States, England and Wales, Belgium, Spain, Romania, Hungary, Italy, and northern Greece. Despite