In 2018, a study team including CDC scientists analyzed and published vaccine safety data on adjuvanted pH1N1 vaccines (arenaprix-AS03, Focetria-MF59, and Pandemrix-AS03) from 10 global study sites. Researchers did not detect any associations between the vaccines and narcolepsy.

Incidence rate study data did not show a rise in the rate of narcolepsy following vaccination except in the one signaling country included (Sweden, which used Pandemrix). Case-control analyses for Arepanrix-AS03 did not show evidence of an increased risk of narcolepsy. Case-coverage analysis for Pandemrix-ASO3 in children in the Netherlands did not show evidence of an increased risk of narcolepsy, but the number of exposed cases was small (N=7). Cases-control analysis for Focetria-MF59 did not show evidence of an increased risk of narcolepsy.