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.

Transmission Dynamics and Epidemiological Characteristics of the SARS-CoV-2 Delta Variant ― Hunan Province, China, 2021

Monitoring changes in the epidemiologic features between different severe acute respiratory syndrome coronavirus 2(SARS-CoV-2)variants is key to understanding the evolution of viral fitness in the host population.Here,we analyzed a successfully contained local outbreak of the Delta variant that took place in Hunan,China,in July–August,2021.Detailed data on SARS-CoV-2 infections and their contacts were collected during the outbreak.By leveraging these data,we estimated key epidemiological parameters,including the incubation period,serial interval,and generation time.We constructed a generalized linear mixed-effects model(GLMM)to quantify risk factors for Delta infection and transmission.Between July 28 and August 15,2021,a total of 129 infections and their 2,118 close contacts were identified during the outbreak in Hunan Province.

Integrated Rabies Surveillance-Hunan Province,China,2020

Introduction:The objective of this paper was to assess the epidemiology of rabies in Hunan Province,analyze the associated factors,understand the status of prevention and treatment after rabies exposure,evaluate the effectiveness of prevention and treatment,and provide a scientific basis for formulating effective prevention and control measures.Methods:The surveillance data of rabies in Hunan Province in 2020 were collected and analyzed by descriptive epidemiological method.Results:In 2020,a total of 59 cases of rabies were reported in Hunan Province,with an incidence rate of 0.09/100,000.Overall,42 cases(71.19%)were due to animal bites and 43 cases(72.88%)were of grade III.The proportion of hand and combined injury of hand was the highest(40.68%).A total of 603,261 cases of rabies exposure were reported from the rabies post-exposure prophylaxis(PEP)clinic in Hunan Province.Dogs were the main animal causing injuries,accounting for 74.21%.Only 83,418(13.84%)of the animals had a clear immune history,and a total of 11 dog attacks were reported in Hunan Province.The average immunity rate of dogs in the whole province was 30.98%.In 2020,554 dogs were sampled in the whole province;20 of them were positive for a positivity rate of 3.61%.Conclusions:Rabies in Hunan Province in 2020 had a relatively low prevalence.Failure to treat wounds,immunoglobulin injections,and vaccination after exposure were the main causes of rabies.Therefore,post-exposure management of rabies should be further strengthened to reduce the risk of rabies for high-risk populations.