Reports of multiple sclerosis (MS) developing after hepatitis B vaccination raised the concern that this vaccine can cause MS in previously healthy subjects. Two studies published in the 1 February issue of the
Christian Confavreux from Hôpital Neurologique, Lyons, France, and colleagues from the Vaccines in Multiple Sclerosis Study Group, investigated 643 European patients with multiple sclerosis. They found a 0.71 relative risk of relapse associated with exposure to any vaccination during the previous two months (95% confidence interval, 0.40 – 1.26). There was no increase in the specific risk of relapse associated with tetanus, hepatitis B, or influenza vaccination (range of relative risks, 0.22 – 1.08). Analyses based on risk periods of one and three months yielded similar results (
Meanwhile, in a case-control study, Alberto Ascherio and colleagues from Harvard Medical School, Boston reviewed the cases of 192 nurses in the US with multiple sclerosis and 645 matched controls. They found a 0.9 (95% confidence interval, 0.5 – 1.6) relative risk of multiple sclerosis associated with exposure to the hepatitis B vaccine at any time before the onset of the disease (
These negative studies also serve to illustrate how hypotheses can become 'facts' long before the critical data are in.