While the concept of attributable risk represents
basic epidemiologic knowledge,4 very
few published vaccine studies include information
about it; most of them present total
postimmunization events in vaccinees. As an
example, in a search in MEDLINE in April
1999 that used the keywords “Hepatitis B vaccine,”
“safety,” and “safe,” we retrieved 365
papers with an abstract, but in only 7 of them
(2%) were there sufficient data for attributable
risk to be calculated (although the attributable
risk was not calculated in most of these
papers).