Spontaneous reporting of suspected narcolepsy after vaccination against pandemic influenza A (H1N1) in Germany.

PURPOSE

We aimed at investigating whether, in Germany, the number of individual case safety reports (ICSR) of confirmed narcolepsy following Pandemrix® vaccination notified to the Paul-Ehrlich-Institut (PEI, German Federal Institute for Vaccines and Biomedicines) was higher than expected when compared with the prepandemic background incidence rates.

METHODS

ICSR of narcolepsy after vaccination with Pandemrix® notified to the PEI until September 2016 were reviewed and validated according to the criteria of narcolepsy defined by the Brighton Collaboration (BC). Cases fulfilling the criteria of BC levels of diagnostic certainty 1 to 4a with symptoms onset after vaccination with Pandemrix® were eligible. Adjustment for underreporting was performed with cases of narcolepsy recruited within the scope of the German Narcolepsy Study using capture-recapture methods. An observed versus expected (OvE) analysis was conducted based on adjusted case numbers using risk windows for symptoms onset within 4 and 6 months following vaccination.

RESULTS

By the end of September 2016, a total of 85 ICSR of narcolepsy after vaccination with Pandemrix® had been notified to the PEI 52 of which were eligible. The OvE estimates for the 4 and 6 months risk windows were 3.8 (95% CI: 2.6-5.4) and 2.8 (95% CI: 2.0-3.9), respectively. The number of excess cases was higher in children and adolescents (15-fold and 11.7-fold increased OvE estimate) than in adults (2.1-fold and 1.5-fold increased estimate).

CONCLUSIONS

Compared with the prepandemic background incidence rate, the number of incident narcolepsy cases was 3.8-fold and 2.8-fold as high.