TABLE 3.

Comparison of amino acid sequences for the HA1 subunit of H1N1 isolates collected from 2002 to 2006

Group	Strain	Substitution at the following amino acid residue in HA1 (H3 numbering)a:
		77	81d	90	101	133	144	149	158	169	190	197	212	255	256	270
	A/New Caledonia/20/99b	E	K	T	Y	V	K	R	N	V	N	T	R	W	Y	T
I	A/Hanoi/1892/02	—c	—	—	—	—	—	—	—	A	D	—	—	R	—	—
I	A/Hanoi/1863/02	—	—	—	—	—	—	—	—	A	—	—	—	R	—	—
II	II A/Hanoi/1873/02	—	—	—	—	—	—	—	S	A	—	—	—	R	—	—
II	A/Hanoi/719/03	—	—	—	—	—	—	—	S	A	D	—	—	R	—	—
II	A/Hanoi/784b/03	—	—	—	—	—	—	—	S	A	V	—	—	R	—	—
III	III A/Hanoi/ISBM15/05	—	—	—	—	—	—	—	—	A	—	—	—	R	F	—
III	A/Hanoi/TX09/06	—	—	—	—	—	—	—	—	A	D	—	—	R	F	—
III	A/Hanoi/Q177/06	—	—	—	—	—	—	—	K	A	D	—	—	R	F	—
IV	IV A/Hanoi/BM344/06	D	R	K	H	T	E	K	—	A	D	—	K	R	—	N
IV	A/Solomon Islands/3/06	—	R	K	H	T	E	K	—	A	D	K	K	R	—	N

^aResults are reported as amino acid differences between the sequences of the isolates and that of the A/New Caledonia/20/99 vaccine strain.

^bItalic type indicates the reference vaccine strain.

^c—, no change.

^dDifferences located in the proposed antigenic sites are underlined.