Timeline of the vaccination, intervention and blood collection.

<p>The study was composed of two phases. In phase 1, one prophylactic and one control group were investigated. In phase 2, one prophylactic paracetamol, one therapeutic paracetamol and one control group were investigated. The paracetamol groups received paracetamol after the primary and first booster hepatitis B vaccine doses, at 0 and 1 month. Participants received no paracetamol after the second booster vaccine dose at 6 months. The control group received no paracetamol or placebo during the hepatitis B vaccination procedure. Blood (14–21 mL) was taken of all participants prior to and one month after the second booster vaccination.