Table 1. Positive rate and GMT of 2009 H1N1 virus antibody in a follow-up study of natural infection patients and vaccinated people, Guangzhou, 2009.

Group	total	positive rate					GMT
		day15	day30	day180	χ2		day15	day30	day180	T value
					day15 vs day30	day30 vs day180				day15 vs day30	day30 vs day180
natural infection	129	60	100	52	23**	38**	63	80	52	0.92	4.5**
vaccination	86	78	81	34	0.32	39**	100	193	74	4.5**	5.1**

*p<0.05,

**p<0.01.