Vaccination and Autoimmune Demyelination: Little if Any Risk

摘要

In a large case-centered study, no attributable risk for transverse myelitis was found with vaccination. There was an attributable risk of <4 cases per 10 million doses for Tdap causing acute disseminated encephalitis. Despite little supportive evidence, vaccinations are often avoided because of persistent concerns about triggering an autoimmune acute demyelinating event (ADE). Studies focusing on the association between ADEs and vaccinations are problematic because large numbers of subjects are required and because the ADE may occur many years after vaccination. However, conditions that have an abrupt onset, such as transverse myelitis (TM) and acute disseminated encephalomyelitis (ADEM), are amenable to study of whether vaccines have an association. In a collaborative effort between Kaiser Permanente and the CDC, researchers used a case-centered design to examine the Vaccine Safety Datalink of more than 9 million patients and nearly 64 million vaccine doses, aiming to ascertain if there was an association between any vaccination given and subsequent TM or ADEM. The interval of 5 to 28 days after vaccination was deemed most likely to identify a demyelinating disease associated with the vaccination. The researchers compared the incidence of events in this time period with events occurring between 43 days and 9 months after vaccination. All subjects had at least one vaccination during the study period. Overall, 67 TM and 47 ADEM cases occurring within 9 months after a vaccination were identified. The risk for TM among those immunized in the 5- to 28-day exposure interval was not significantly increased compared with those immunized during the rest of the 9-month interval studied. For ADEM, Tdap vaccine was significantly associated with an increased risk during the 5- to 28-day interval but not during an expanded 2- to 42-day interval. The excess risk for ADEM attributable to Tdap was 0.385 per million doses.