Effectiveness of the pandemic H1N1 influenza vaccines against laboratory-confirmed H1N1 infections: Population-based case-control study

► We evaluated the effectiveness of the H1N1 vaccine used in the recent pandemic. ► The study outcome was laboratory-confirmed H1N1 infections. ► The adjuvanted H1N1 vaccine was 86% effective in preventing these infections. ► Effectiveness seemed lower among older (≥50 years) individuals (51%).