Figure 2

Anti-influenza antibodies in young children and in young adults, 2002 and 2007. Children (1-3-years-old, a) and adult (35-50-years-old, b) sera obtained in 2002 and in 2007 were tested by the HI test against A/Wisconsin/67/2005 (black columns), and A/Panama/2007/99 (gray columns). * <0.0013, ** <0.01, *** <0.0001 using Chi test.