高免疫人群甲肝爆发特点与免疫屏障作用

Characteristics of hepatitis A outbreak and effect of "herd immunity barrier" in population with high immunity

作者调查了西安市3个甲肝高免疫人群中的流行前群体免疫为75.8％～92.3％,罹患率为14.7‰～57.1‰,流行持续时间为10～31d;而3个低免疫人群的流行前群体免疫为30.0％～57.1％,罹患率为140.6‰～444.4‰,持续时间为10～117d。罹患率与流行前群体免疫呈非常显著的负相关(P<0.01)。作者认为,自然感染获得的免疫在人群中达到一定水平,如同预防接种一样,可形成“人群免疫屏障”,高免疫人群甲肝爆发的特点(罹患率低,持续时间短)与免疫水平及其免疫屏障作用有关。但这种屏障作用是相对的,因此,作者讨论了甲肝流行时相应的对策。

Among 3 communities with a high level of herd immunity of hepatitis A in Xi'an, the herd immunity before epidemic (pre-epidemic prevalence) ranged between 75.8% and 923% while the attack rate varied from 14.7 ‰ to 57.1 ‰ and the epidemic lasted from 10 to 31 days. In contrast, among 3 communities with a low level of herd immunity, the herd immunity before epidemic ranged between 30.0% and 57.1% while the attack rate varied from 140.6‰ to 4444 ‰ and the epidemic duration was from 10 to 117 days. There was a very significant negative association between the attack rate and the herd immunity (P<0.01). Authors considered that the herd immunity up to a given level acquired by natural infection could 'establish a 'herd immunity barrier'in a community just as in the case after vaccination. In the community with a high level of herd immunity, hepatitis A is characterized by lower attack rate and shorter epidemic duration. These characteristics are associated with the level of immunity and the effect of 'herd immunity barrier'. But the effect was relative, hence the corresponding control strategies are discussed in the paper.