. 2012 Feb 6;7(2):e31162. doi: 10.1371/journal.pone.0031162

Table 3. Comparison of the percentages of the pH1N1-E374K mutants in HA2 and other variants at the four antigenic sites and their relationships with different intervention strategies in various epidemic periods, 2009–2010.

		Percentages of Mutants
Periods	Intervention Strategies	HA2		HA1
		Number of isolates	E374K	Number of isolates	Ca	Cb	Sa	Sb
Before Aug. 1, 2009	No any intervention	17	0 (0%)¹	17	4^* (23.3%)³	0 (0%)	2^* (11.8%)³	1 (5.9%)
Aug 1–Nov. 18, 2009	Start to pay Tamiflu by National health Insurance	123	32 (26.0)%	101	9 (9.2)%	2 (2.0%)	1 (1.0%)	1 (1.0%)
Nov.19–Dec 19, 2009	Implement of vaccination in 6–18 years old	9	7 (77.8%)²	9	2 (22.2%)⁴	0 (0%)	0 (0%)⁴	0 (0%)
After Dec 19, 2009	Post nation- wide vaccination campaign	47	34 (72.3%)	47	4^** (8.5%)	0 (0%)	11^** (23.4%)	1 (2.1%)

. The effect of intervention of antiviral agent on the percentages of E374K mutants: Before (0%, 0/17) vs after (40.78%, 73/179), p<0.001 (Fisher's exact test).

. The effect of intervention of vaccination on the percentages of E374K mutants: Before (22.86%, 32/140) vs after (72.34%, 41/56), p<0.001 (Fisher's exact test).

. The effect of intervention of antiviral agent on the percentages of the pH1N1 variants with substitutions at four antigenic sites (Ca, Cb, Sa, Sb): Before (29.41%, 5/17) vs after (17.83%, 28/157), p = 0.324 (Fisher's exact test).

⁴

. The effect of intervention of vaccination on the percentages of the pH1N1 variants with substitutions at four antigenic sites (Ca, Cb, Sa, Sb): Before (11.86%, 18/118) vs after (25%, 15/56), p = 0.097 (Fisher's exact test).

*: Two strains with double mutations in Ca and Sa sites.

**: Three strains with double mutations in Ca and Sa sites.