Reassessment of the association between Guillain-Barré syndrome and receipt of swine influenza vaccine in 1976-1977: results of a two-state study. Expert Neurology Group.

Although the original Centers for Disease Control study of the relation between A/New Jersey/8/76 (swine flu) vaccine and Guillain-Barré syndrome (polyradiculoneuritis) demonstrated a statistical association and suggested a causal relation between the two events, controversy has persisted. To reassess this association, the authors obtained medical records of all previously reported adult patients with Guillain-Barré syndrome in Michigan and Minnesota from October 1, 1976 through January 31, 1977. To identify previously unreported hospitalized cases with onset of symptoms during this period, the authors surveyed medical care facilities. A group of expert neurologists formulated diagnostic criteria for Guillain-Barré syndrome and then reviewed the clinical records in a blinded fashion. Of the 98 adult patients from the original Centers for Disease Control study eligible for consideration, three were found to have been misclassified by date of onset and were excluded. Of the remaining 95, the 28 (29%) who did not meet the diagnostic criteria were equally distributed between the vaccinated group (18 of 60, 30%) and the unvaccinated group (10 of 35, 29%). In addition to the 67 remaining cases who met the diagnostic criteria, six previously unreported cases (three of whom had been vaccinated) were found and included in this analysis. The relative risk of developing Guillain-Barré syndrome in the vaccinated population of these two states during the 6 weeks following vaccination was 7.10, comparable to the relative risk of 7.60 found in the original study. These findings suggest that there was an increased risk of developing Guillain-Barré syndrome during the 6 weeks following vaccination in adults. The excess cases of Guillain-Barré syndrome during the first 6 weeks attributed to the vaccine was 8.6 per million vaccinees in Michigan and 9.7 per million vaccinees in Minnesota. No increase in relative risk for Guillain-Barré syndrome was noted beyond 6 weeks after vaccination.

Guillain-Barré syndrome and its relationship to swine influenza vaccination in Michigan, 1976-1977.

Active surveillance to detect all patients with Guillain-Barré syndrome who had had onset of illness from July 1, 1976 through April 30, 1977 was undertaken in Michigan after indications that the syndrome might be associated with the National Influenza Immunization Program of 1976-1977. Hospital record room librarians, neurologists, and neurosurgeons reported the greatest number of cases; coded hospital discharge records were the best means of ascertaining case occurrence. This differed from national surveillance, which relied essentially on reports that neurologists and other clinicians sent to state epidemiologists and then to the Centers for Disease Control; hospital discharge lists were not systemically reviewed nationally. A total of 79 of the Michigan cases were in persons who had not received swine influenza vaccine, while 46 cases were in persons who had received it. For unvaccinated adults, the incidence of Guillain-Barré syndrome during the 10-month surveillance period was 0.36 cases per 10(6) person-weeks; for adults with onset within six weeks of vaccination, it was 2.31 cases per 10(6) person-weeks. After six weeks post-vaccination, the rate decreased to 0.17 cases per 10(6) person-weeks. The attributable risk for acquiring Guillain-Barré syndrome within six weeks after receiving swine influenza vaccine was 11.70 cases per 10(6) persons vaccinated.

Liver function abnormalities in the course of a type A (H1N1) influenza outbreak: relation to Reye's syndrome.

In the course of the A/Brazil (H1N1) outbreak of 1978-1979, two cases of Reye's syndrome occurred in Grayling, Michigan, an area with a county-wide population of 2056 school age children. School absenteeism peaked at levels between 16-28 per cent. Clinical histories and paired blood specimens were collected from 860 school children; the initial blood was obtained shortly after the peak of the outbreak. Serologic results confirmed that type A H1N1 virus was the cause of the outbreak. Serum alanine aminotransferase (SGPT) and creatine phosphokinase (CPK) values were determined on all initial blood specimens and a sample of the second specimens. CPK results did not correlate with infection, illness or SGPT values. SGPT values of 60 IU/l or greater were found in 1.5 per cent of those tested. The elevated values were not associated with illness but were associated with influenza infection. Based on the excess number with elevated results in those with recent infection, it is estimated that at least 2.7 per cent of individuals infected by type A (H1N1) influenza had associated elevated SGPT.