流感大流行期间疫苗免疫方案的传染病模型

The Epidemic Model of Influenza Vaccination Programs in Pandemic Influenza

目的模拟流感大流行期间疫苗免疫方案控制疫情的效果,对比两种疫苗免疫方案的效果差异,为制订应急方案提供数据参考。方法基于传染病的自然规律,在传统SEIR模型的基础上建立对人群免疫的传染病模型,采用感染率(AR)作为判断指标,对全人群免疫和部分人群免疫(排除康复人群)两种免疫方案进行效果对比。结果对于R0在2左右的流感大流行,感染者均表现临床症状的情况下,随着疫苗延迟时间(TL)和完成时间(DV)的缩短,感染率下降。当控制目标设定为将感染率控制在50%以下时,采用全人群免疫方案的最大TL和DV组合为40和30 d;采用部分人群免疫方案的最大TL和DV组合为两者均为40 d,或两种方案的TL和DV最大组合均为30和80 d。如果不能在短期内开展和完成疫苗计划(TL在30 d内,DV为20 d内),则部分人群免疫方案可以更快地降低感染率。结论为最大程度地减少大流行期间的生命损失,将感染率控制在50%以下,防病重点应为尽早开展和完成疫苗计划,如果TL在30 d以上,则部分人群的免疫方案更有利于疫情的控制。

Objective To simulate the effect of influenza vaccination programs in controlling pandemic and compare the effects of two different programs for the formulation of emergency response proposals.Methods The dynamic of influenza was simulated using SEIR model based on the natural history of illness and the attack rate（AR） was defined as the evaluating indicator.The effects of two different programs（the whole population will be vaccinated or part of the population besides the rehabilitee will be vaccinated） were compared.Results For pandemic influenza strains with R0 being around 2 and all infected individuals would be symptomatic,with the reduction of the time at which vaccination begins（TL） and the time it takes to vaccinate the entire population（DV）,the AR decreased.If the target of controlling pandemic was set as the AR being kept below 50%,then under condition of the whole population will be vaccinated,the largest combination of TL and DV would be 40 days and 30 days respectively;or under the condition of part of the population will be vaccinated,the largest combination of TL and DV would be 40 and 40,respectively;or either condition the largest combination of TL and DV could be 30 and 80,espectively.If TL and DV couldn′t achieve less than 30 days and 20 days,respectively,then the program with part of the population be vaccinated would be more effective.Conclusion To mitigate the damage of pandemic and keep the AR under 50%,the vaccination program should focus on how to shorten TL and DV.If TL was larger than 30,the program with part of the population be vaccinated would be more effective.