Contact pattern,current immune barrier,and pathogen virulence determines the optimal strategy of further vaccination

Background:The current outbreak of novel coronavirus disease 2019 has caused a seriousdisease burden worldwide.Vaccines are an important factor to sustain the epidemic.Although with a relatively high-vaccination worldwide,the decay of vaccine efficacy andthe arising of new variants lead us to the challenge of maintaining a sufficient immunebarrier to protect the population.Method:A case-contact tracking data in Hunan,China,is used to estimate the contactpattern of cases for scenarios including school,workspace,etc,rather than ordinary susceptible population.Based on the estimated vaccine coverage and efficacy,a multi-groupvaccinated-exposed-presymptomatic-symptomatic-asymptomatic-removed model(VEFIAR)with 8 age groups,with each partitioned into 4 vaccination status groups isdeveloped.The optimal dose-wise vaccinating strategy is optimized based on the currentlyestimated immunity barrier of coverage and efficacy,using the greedy algorithm thatminimizes the cumulative cases,population size of hospitalization and fatality respectivelyin a certain future interval.Parameters of Delta and Omicron variants are used respectivelyin the optimization.Results:The estimated contact matrices of cases showed a concentration on middle ages,and has compatible magnitudes compared to estimations from contact surveys in otherstudies.The VEFIAR model is numerically stable.The optimal controled vaccination strategy requires immediate vaccination on the un-vaccinated high-contact population of age30e39 to reduce the cumulative cases,and is stable with different basic reproductionnumbers(R_(0)).As for minimizing hospitalization and fatality,the optimized strategy requires vaccination on the un-vaccinated of both aged 30e39 of high contact frequencyand the vulnerable older.Conclusion:The objective of reducing transmission requires vaccination in age groups ofthe highest contact frequency,with more priority for un-vaccinated than un-fully or fullyvaccinated.The objective of reducing total hospitalization and fatality requires not only toreduce transmission but also to protect the vulnerable older.The priority changes byvaccination progress.For any region,if the local contact pattern is available,then with thevaccination coverage,efficacy,and disease characteristics of relative risks in heterogeneouspopulations,the optimal dose-wise vaccinating process will be obtained and gives hintsfor decision-making.

A follow up study of cycle threshold values of SARS-CoV-2 in Hunan Province,China

Since the epidemic of the severe acute respiratory syndrome coronavirus 2(SARS-COV-2),many governments have used reverse transcription polymerase chain reaction(RT-PCR)to detect the virus.However,there are fewer measures of CT values information based on RT-PCR results,and the relationship between CT values and factors from consecutive tests is not clear enough.So in this study,we analyzed the connection between CT values and the factors based on cohort data from Delta variant of SARS-CoV-2 in Hunan Province.Previous studies have showed that the mean age of the cases was 33.34 years(±18.72 years),with a female predominance(55.03%,n=71),and the greatest proportion of clinical symptoms were of the common type(60.47%,n=78).There were statistical differences between the N and ORF1ab genes in the CT values for the cases.Based on the analysis of the association between CT values and the factors,the lowest CT values were obtained for the unvaccinated,older and clinically symptomatic group at 3e10 days,the maximum peak of viral load occurred.Therefore,it is recommended to use patient information to focus on older,clinically symptomatic,unvaccinated patients and to intervene promptly upon admission.

Transmissibility of tuberculosis among students and non-students:an occupational-specific mathematical modelling

Background: Recently, despite the steady decline in the tuberculosis (TB) epidemic globally, school TB outbreaks have been frequently reported in China. This study aimed to quantify the transmissibility ofMycobacterium tuberculosis (MTB) among students and non-students using a mathematical model to determine characteristics of TB transmission.Methods: We constructed a dataset of reported TB cases from four regions (Jilin Province, Xiamen City, Chuxiong Prefecture, and Wuhan City) in China from 2005 to 2019. We classified the population and the reported cases under student and non-student groups, and developed two mathematical models [nonseasonal model (Model A) and seasonal model (Model B)] based on the natural history and transmission features of TB. The effective reproduction number (R(eff)) of TB between groups were calculated using the collected data.Results: During the study period, data on 456,423 TB cases were collected from four regions: students accounted for 6.1% of cases. The goodness-of-fit analysis showed that Model A had a better fitting effect (P < 0.001). The average R_(eff) of TB estimated from Model A was 1.68 [interquartile range (IQR): 1.20–1.96] in Chuxiong Prefecture, 1.67 (IQR: 1.40–1.93) in Xiamen City, 1.75 (IQR: 1.37–2.02) in Jilin Province, and 1.79 (IQR: 1.56–2.02) in Wuhan City. The average R_(eff) of TB in the non-student population was 23.30 times (1.65/0.07) higher than that in the student population.Conclusions: The transmissibility of MTB remains high in the non-student population of the areas studied, which is still dominant in the spread of TB. TB transmissibility from the non-student-to-student-population had a strong influence on students. Specific interventions, such as TB screening, should be applied rigorously to control and to prevent TB transmission among students.

Feasibility of Booster Vaccination in High-Risk Populations for Controlling Coronavirus Variants—China,2021

Introduction:Vaccination booster shots are completely necessary for controlling breakthrough infections of severe acute respiratory syndrome coronavirus 2(SARS-CoV-2)in China.The study aims to estimate effectiveness of booster vaccines for high-risk populations(HRPs).Methods:A vaccinated Susceptible-Exposed-Symptomatic-Asymptomatic-Recovered/Removed(SEIAR)model was developed to simulate scenarios of effective reproduction number(Reff)from 4 to 6.Total number of infectious and asymptomatic cases were used to evaluated vaccination effectiveness.Results:Our model showed that we could not prevent outbreaks when covering 80%of HRPs with booster unless Reff=4.0 or the booster vaccine had efficacy against infectivity and susceptibility of more than 90%.The results were consistent when the outcome index was confirmed cases or asymptomatic cases.Conclusions:An ideal coronavirus disease 2019(COVID-19)booster vaccination strategy for HRPs would be expected to reach the initial goal to control the transmission of the Delta variant in China.Accordingly,the recommendation for the COVID-19 booster vaccine should be implemented in HRPs who are already vaccinated and could prevent transmission to other groups.

Modeling Cross-Regional Transmission and Assessing the Effectiveness of Restricting Inter-Regional Population Movements in Controlling COVID-19-Xi’an City,Shaanxi Province,China,2021

Introduction:The aim of this study was to construct an assessment method for cross-regional transmission of coronavirus disease 2019(COVID-19)and to provide recommendations for optimizing measures such as interregional population movements.Methods:Taking Xi’an City as the example subject of this study’s analysis,a Cross-Regional-Gravitational-Dynamic model was constructed to simulate the epidemic in each district of Xi’an under three scenarios of controlled population movement(Scenario 1:no intensive intervention;Scenario 2:blocking Yanta District on December 18 and blocking the whole region on December 23;and Scenario 3:blocking the whole region on December 23).This study then evaluated the effects of such simulated population control measures.Results:The cumulative number of cases for the three scenarios was 8,901,425,178,and 474,respectively,and the duration of the epidemic was 175,18,and 22 days,respectively.The real world prevention and control measures in Xi’an reduced the cumulative number of cases for its outbreak by 99.98%in comparison to the simulated response in Scenario 1;in contrast,the simulated prevention and control strategies set in Scenarios 2(91.26%)and 3(76.73%)reduced cases even further than the real world measures used in Xi’an.Discussion:The constructed model can effectively simulate an outbreak across regions.Timely implementation of two-way containment and control measures in areas where spillover is likely to occur is key to stopping cross-regional transmission.