Discussion
ApreviousreviewofstudiesonEngerix- Bhadshownthatthisvaccinewasverysafein neonates and adults.3 In the present study, Engerix-Bwasalsosafeinpreadolescents,with a low but significant frequency of headaches andgastrointestinalproblemsattributabletothe vaccine.Evenifparentswereinstructedtore- cordeveryhealthproblem,theinformationwas dependentontheirsubjectiveappraisalofwhat constitutes a health problem and on how dili- gentlytheyrecordeddata.Theyprobablyhada greatersensitivityforadverseeventsaftervac- cination,abiasthatwouldoverestimatetherisk duetovaccination.Inspiteofthat,weobserved onlyaminimalincreaseintheincidenceofad- verseeventsduringtheweekaftervaccination compared with that of the week preceding it, confirmingthesafetyofthisvaccine.