Author Affiliations: sanofi pasteur, Swiftwater, Pennsylvania.
We note methodological issues with the study by Farez and Correale.1 They observed relapses of multiple sclerosis (MS) in 5 of 7 patients with MS after yellow fever (YF) vaccination and used a self-controlled case series method to elucidate a possible association. They also selected matched controls among healthy subjects and patients with MS vaccinated with inactivated influenza vaccine for comparison of immunological responses to vaccination.
Pool V, Gordon DM, Decker M. Methodological Issues With the Risk of Relapse Study in Patients With Multiple Sclerosis After Yellow Fever Vaccination. Arch Neurol. 2012;69(1):144-145. doi:10.1001/archneurol.2011.1519