We introduced an editorial error into this Clinical Review by Douglas Fleming at proof stage (BMJ 2005;331:1066-9, 5 Nov). While rephrasing a sentence, we omitted the word "not." So in the box titled "Learning point: Example 4" the penultimate sentence wrongly read: "Pregnancy is a contraindication for vaccination." It should have read: "Pregnancy is not a contraindication for vaccination." In addition, a few words from the main article appeared with the text of the same learning point box. These errors have now been corrected in the HTML and PDF versions of the article on bmj.com.