Question: is this a 2) strong advice, 1) weak advice 0) no advice?

Furthermore, an optimal capability of the HBV booster vaccine to elicit a strong anamnestic immune response was demonstrated, particularly in subjects receiving the primary immunization course during adolescence.19 Indeed, in our study, more than 95% of subjects receiving an HBV vaccine booster dosed demonstrated a seroprotective anti-HBs antibody titer after 2 weeks from vaccination, and all subjects vaccinated in adolescence reached a seroprotective anti-HBs antibody titer. 
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This is no advice
assistant