. Author manuscript; available in PMC: 2012 Sep 1.

Published in final edited form as: Clin Microbiol Infect. 2011 Jul 13;17(9):1347–1349. doi: 10.1111/j.1469-0691.2011.03538.x

TABLE 2.

Serum antibodies to pandemic (H1N1) 2009 virus A/California/07/2009

Collection place	Collection date	No. of subjects	Positive number at different HI (rate, 95%CI)
Collection place	Collection date	No. of subjects	HI≥10	HI≥20	HI≥40	HI≥80
Jiangsu^a	March 2009	1571	52 (3.3%,2.5-4.3)	25 (1.6%,1.0-2.3)	9 (0.6%,0.3-1.1)	2 (0.1%,0.0-0.5)
	May 2010	9936	1385 (13.9%,13.3-14.6)^*	874 (8.8%,8.2-9.4)^*	448(4.5%,4.1-4.9)^*	182(1.8%,1.6-2.1)^*
Jiangsu serial^b	March 2009	1295	43 (3.3%,2.4-4.4)	20 (1.5%,1.0-2.4)	8 (0.6%,0.3-1.2)	2 (0.2%,0.0-0.6)
	May 2010	1295	178 (13.8%,11.9-15.7)^*	119 (9.2%,7.7-10.9)^*	61 (4.7%,3.6-6.0)^*	24 (1.8%,1.2-2.7)^*

Specimens were tested in duplicate.

p<0.01, the unadjusted Chi-square or Fisher’s exact test was used for categorical independent variables. Estimation of the 95% CI was performed with exact binomial methods. Calculations were conducted with SPSS statistical software, version 17.0 (SPSS, Chicago, IL, USA).

1517 and 9936 sera samples were collected from residents of two villages in Jiangsu province, eastern China, in March 2009 and May 2010, respectively. None of the people had a history of influenza vaccination.

Among the 1517 and 9936 sera samples, there are 1295 serial sample pairs taken from the same individuals in 2009 and 2010, respectively.