BACKGROUND: Observational studies report that influenza vaccination reduces winter mortality risk from any cause by 50% among the elderly. Influenza vaccination coverage among elderly persons (>or =65 years) in the United States increased from between 15% and 20% before 1980 to 65% in 2001. Unexpectedly, estimates of influenza-related mortality in this age group also increased during this period. We tried to reconcile these conflicting findings by adjusting excess mortality estimates for aging and increased circulation of influenza A(H3N2) viruses.

METHODS: We used a cyclical regression model to generate seasonal estimates of national influenza-related mortality (excess mortality) among the elderly in both pneumonia and influenza and all-cause deaths for the 33 seasons from 1968 to 2001. We stratified the data by 5-year age group and separated seasons dominated by A(H3N2) viruses from other seasons. RESULTS: For people aged 65 to 74 years, excess mortality rates in A(H3N2)-dominated seasons fell between 1968 and the early 1980s but remained approximately constant thereafter. For persons 85 years or older, the mortality rate remained flat throughout. Excess mortality in A(H1N1) and B seasons did not change. All-cause excess mortality for persons 65 years or older never exceeded 10% of all winter deaths.

CONCLUSIONS: We attribute the decline in influenza-related mortality among people aged 65 to 74 years in the decade after the 1968 pandemic to the acquisition of immunity to the emerging A(H3N2) virus. We could not correlate increasing vaccination coverage after 1980 with declining mortality rates in any age group. Because fewer than 10% of all winter deaths were attributable to influenza in any season, we conclude that observational studies substantially overestimate vaccination benefit.

BACKGROUND: Transverse myelitis has been reported in association with vaccination, including influenza vaccination.

OBJECTIVE: To describe a case of longitudinally extensive transverse myelitis associated with vaccination with a nasal attenuated novel influenza A(H1N1) vaccine.

DESIGN: Case report.

SETTING: Sanford University of South Dakota Hospital. Patient A 27-year-old woman with longitudinally extensive transverse myelitis.

RESULTS: Four days following novel influenza A(H1N1) vaccination, the patient developed longitudinally extensive transverse myelitis. Extensive diagnostic evaluation effectively ruled out causes other than vaccination-associated transverse myelitis. Following treatment with corticosteroids and plasmapheresis, the patient made a significant recovery.

CONCLUSIONS: Transverse myelitis may be associated with vaccination against novel influenza A(H1N1). Additionally, we believe this to be the first report of longitudinally extensive transverse myelitis associated with any vaccine.