MS and the Yellow Fever Vaccine

Although common vaccines are safe for use in multiple sclerosis, a recent study in the Archives of Neurology (online June 2011) indicates that the Yellow Fever vaccine can increase relapse rate in travelers with MS.  This study was conducted by the same researchers who undertook the meta-analysis referenced above.

Seven patients with RRMS who were traveling to areas where yellow fever is endemic received the yellow fever vaccine and were observed for two years.  To serve as controls, twenty-one additional patients were included: 7 healthy individuals who were age- and sex-matched, 7 MS patients who received flu vaccines according to WHO (World Health Organization) recommendations, and 7 MS patients who receive no vaccines.

Patients were told to report exacerbations within 72 hours, otherwise they were examined every 3 months for 2 years.  MRI scans were conducted 3 months and 9 months following vaccination, and were compared to scans conducted 12 months prior to the beginning of the study.  Relapses were analyzed both during the “at risk period” which was weeks 1-5 following vaccination and the “non-risk period” which was the remaining time of weeks 6-104.  Since the yellow fever vaccine contains a live virus, researchers began measuring the ARP one full week after vaccination.

For the entire 2-year time period, the annual relapse rate was 0.99 with five (of seven) patients experiencing 14 exacerbations.  There were 5 relapses during the at-risk period (annualized relapse rate of 8.57) and 9 relapses during the non-risk period (annualized relapse rate of 0.67).  The exacerbation rate was 12.778 times higher [emphasis mine] during the at-risk period.  Patients also had more lesions 3 months after immunization as compared to 12 months before the study and during the 2-year follow-up.  Two of the seven patients in the test group had no relapses or additional lesions at any time during the study.