Table 3.

Median number of epitopes per virus isolate found conserved in strains from preceding 20 years

Year	Epitope category
	B-cell	T-cell, CD8+	T-cell, CD4+
2000	16	67	84
2001	16	66	82
2002	16	66	93
2003	16	66	96
2004	18	65	92
2005	16	66	96
2006	15.5	66	93.5
2007	14	66	93
2008	16	68	87
Median (2000–2008)	16	66	93
2009, S-OIV	8	54	57

Abbreviation: S-OIV, swine-origin H1N1 influenza virus.