Common side effects in the Italian and Stockholm I trials

We have compared the frequency of common side effects observed following vaccination in the Italian and Stockholm I Trials. A higher proportion of DTPwc vaccinees in the two trials experienced side effects compared with DTaP and DT vaccinees. Fever, local redness and tenderness were more frequently observed in all study groups in the Stockholm I Trial when compared to the Italian Trial. Despite the similarities in study design, parental recall bias, site of injection, simultaneous administration of other vaccines, and antipyretic use could have played a role in the differences observed.