Nationwide oral poliovirus vaccination campaign and the incidence of Guillain-Barré Syndrome.

A retrospective analysis of the incidence of Guillain-Barré syndrome (GBS) in Finland in 1981-1986 was carried out by careful examination of medical records identified from nationwide Hospital Discharge Register data based on a mean total population of 5 million people. Records from 247 patients fulfilled the accepted criteria of GBS corresponding to a mean annual incidence of 0.82 per 100,000 population. Monthly rates showed an increased incidence of GBS in March 1985, following by a few weeks the onset of the nationwide oral poliovirus vaccine campaign and partly overlapping it. Analysis of the time series in depth suggested, however, that a change point in the occurrence of GBS had already taken place before the oral poliovirus vaccine campaign. Widespread circulation of wild-type 3 poliovirus in the population immediately preceded the oral poliovirus vaccine campaign and the peak occurrence of GBS. These results demonstrate a temporal association between poliovirus infection, caused by either wild virus or live attenuated vaccine, and an episode of increased occurrence of GBS, but they cannot prove the suspected cause-effect relation between GBS and oral poliovirus vaccine administration.