Vaccinations and Multiple Sclerosis

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Abstract
Ascherio et al. (Feb. 1 issue)1 report that they found no association between hepatitis B vaccination and the onset of multiple sclerosis. Vaccination was confirmed only in the respondents who said they had been vaccinated. Exclusions involved only the women with multiple sclerosis or the controls who had potentially been vaccinated, not those stating they had not been vaccinated. Similar rates of exclusion are cited for the women with multiple sclerosis and the controls, but with the wrong denominator, which should have referred to the positive cases and controls. Rather than exclude 35 percent of the women with multiple sclerosis, the study excluded 68 percent of the women with multiple sclerosis who had possible vaccine exposure, as compared with only 50 percent of the controls with possible exposure. With the new figures, the odds ratio decreases from 1.9 (95 percent confidence interval, 1.1 to 3.3) to 0.7 (95 percent confidence interval, 0.3 to 1.7).