摘要：Sporadic cases of paralytic poliomyelitis are being reported with increasing frequency, particularly in unvaccinated persons, in several countries in which the disease had been absent for several years following adequate initial vaccination programmes. In Ontario, two paralytic cases occurred in unvaccinated children after several disease-free years. Detailed studies of the strains of poliovirus type 1 isolated from these patients showed that they were not vaccine strains. Contact surveillance in one case showed that 21 originally unvaccinated contacts were also excreting virulent virus. Full text Full text is available as a scanned copy of the original print version. Get a printable copy (PDF file) of the complete article (649K), or click on a page image below to browse page by page. Links to PubMed are also available for Selected References . 245 246 247 248 249 250
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