Analysis of transmission dynamics and effectiveness of control of local epidemics caused by the Omicron BA.2 and BA.5.2 COVID-19 strains in Fujian Province / 中国人兽共患病学报

This study evaluated the scientific nature and effectiveness of iterative optimization of prevention and control measures for local outbreaks caused by the BA.2 and BA.5.2 COVID-19 strains in Fujian Province in 2022,to provide a scientif-ic basis for responding to future new or recurrent respiratory infectious diseases.According to the theory of infectious disease dynamics,relevant information regarding the local epidemic situation caused by the BA.2 sub-type Omicron virus strain in March 2022 and BA.5.2 sub-type Omicron virus strain in October 2022 in Fujian Province was collected.The susceptible exposed infectious removed(SEIAR)model of COVID-19 infection with a latent period and asymptomatic infected persons was used to analyze the transmission dynam-ics of two local epidemic situations,and evaluate the preven-tion and control effects.The incubation period of the BA.2 epidemic was 3 days(1～9 days),the intergenerational inter-val was 3 days(1～5 days),and the initial Rt was 3.0(95％CI:2.7～3.3).The incubation period of the BA.5.2 epidemic was 2 days(1～6 days),the intergenerational interval was 1 day(0～2 days),and the initial R,was 1.9(95％CI:1.7～2.1).The fittingresults for the BA.2 and BA.5.2 epidemics were good,and no statistical difference was observed between the predic-ted and actual numbers of cases(x2BA.2=31.53,x2BA.5.2=27.88,P＞0.05).If an emergency response had not been initiated,the BA.2 epidemic would have continued to spread andpeak on April 7th,with an estimated 638 035 cases.The BA.5.2 epidemic would have rapidly spread,reaching a peak on November 14th,with an estimated 685 940 cases.If one incubation period were detected early,the scale of the BA.2 epidemic would have decreased by 25.73％;if two incubation periods were detected early,the scale would have decreased by 79.56％,and if one incubation period had been delayed,the scale would have expanded by 13.72％.If one incubation period had been detected early in the BA.5.2 epidemic,the scale would have decreased by 35.04％;if two incubation periods had been detected early,the scale would have decreased by 92.47％;and if one incubation period had been delayed,the scale would have increased by 19.75％.The guiding ideology,and the prevention and control measures for handling two local epidemics were optimized and iterated.Our study indicated that implementing the"four early"measures ef-fectively decreased the scale of the epidemic,and earlier detection was associated with more significant control effects.This study provides valuable information for the prevention and control of new or recurrent respiratory infectious diseases.

Evaluation of the effect of varicella outbreak control measures through a discrete time delay SEIR model / 中华预防医学杂志

<p><b>OBJECTIVE</b>forecast the epidemic trend and to evaluate the effect of outbreak control measures by investigation of a varicella outbreak event with a discrete time delay SEIR model.</p><p><b>METHODS</b>A discrete time delay model was formulated by discretization method based on a continuous SEIR model with the consideration of the time delay effect on latent period and communicable period. The epidemic trend forecast was carried out based on the number of expected cases. The theoretical effect evaluation was assessed by comparing the results from different emergency control measures.</p><p><b>RESULTS</b>Without any control measures, the theoretical attack rate was 30.16% (504/1671). The course of the epidemic lasted for 4 months and the peak epidemic time was 78 days after the onset of the first case. 'Generation' phenomenon had been observed in the course of the epidemic with the interval of two weeks. The actual number of cases was decreased by 89.48% (451/504) compared with the number of expected cases under no control measure scenario. With the rigorous quarantine measure for all cases on their onset day, when the measure was conducted on 0, 14, 28, 42 days after the onset of the first case, the total numbers of expected cases were 22, 59, 127 and 220 respectively. With the quarantine measure conducted on 14 days after the onset of the first case, when the proportion of quarantine was 30%, 50%, 70%, 90%, the total number of expected cases were 485, 457, 386 and 169, respectively. With the emergent vaccination for all persons, when the measure was conducted on 0, 14, 28, 42 days after the onset of the first case, the total numbers of expected cases were 7, 26, 81 and 202 respectively. With the emergent vaccination conducted on 14 days after the onset of the first case, when the immunization coverage rate was 30%, 50%, 70%, 90%, the total numbers of expected cases were 354, 246, 127 and 40, respectively.</p><p><b>CONCLUSION</b>The number of expected cases can be regarded as the reference to evaluate the effect of control measures. The simulation results suggest that it will get more benefits to conduct control measures earlier in varicella outbreak events, and the effect of emergent vaccination is better than that of quarantine measure under the same conditions.</p>

Design of field studies on vaccines which involves capturing indirect effect / 中华流行病学杂志

For most variety of vaccines, two types of effects-direct and indirect, can result from immunization programs. Unimmunized individuals in the population that receive immunization program can benefit from the vaccines in addition to the protection from immunization.The classical vaccine trails allocate individuals into study and control arms with individual randomization, so the programs' cost-benefit is underestimated due to the impossible measurement on indirect effect. The objectives of the present work are to introduce the conceptual framework,developed by Halloran et al, for four types of study designs that differentiate and account for direct,indirect, total and overall effects of intervention programs, and to explain the relationships of these effects as well. With the examples of field trails of oral cholera vaccines in Bangladesh and Vi typhoid vaccine in India, further issues refer to the identification of indirect effect. The application in practice is also discussed.

Comparison of mail and meeting forms in evaluation of Delphi study / 浙江大学学报·医学版

<p><b>OBJECTIVE</b>To evaluate and compare mail and meeting forms in evaluation of Delphi study.</p><p><b>METHODS</b>Delphi study by mail and meeting approaches was used to determine the health information dataset. Experts were required to grade the listed items through three indexes: importance, necessity and availability. Study duration, coefficient of variation of items, authority coefficient and coordination coefficient of the experts' opinion of two forms of study were calculated and compared.</p><p><b>RESULT</b>The study duration was four months through mail form and 2 days through meeting. Compared with the first round, the coefficient of variation decreased (P<0.001, all of the three indexes by two forms), and the cooperation index increased (P<0.005) in the second round. The experts' opinions were easier to be consistent through meeting than through mail(P<0.033). And the authority coefficient by meeting consultation (0.83 ± 0.05) was higher than that by mail (0.77 ± 0.03) (P=0.001).</p><p><b>CONCLUSION</b>Both mail and meeting forms of Delphi study can determine the health information dataset,but meeting consultation is better and requires shorter study duration.</p>