Background: Reaching optimal vaccination rates is an essential public health strategy to control the coronavirus disease 2019 (COVID-19) pandemic. This study aimed to simulate the optimal vaccination strategy to contr...Background: Reaching optimal vaccination rates is an essential public health strategy to control the coronavirus disease 2019 (COVID-19) pandemic. This study aimed to simulate the optimal vaccination strategy to control the disease by developing an age-specific model based on the current transmission patterns of COVID-19 in Wuhan City, China.Methods: We collected two indicators of COVID-19, including illness onset data and age of confirmed case in Wuhan City, from December 2, 2019, to March 16, 2020. The reported cases were divided into four age groups: group 1, ≤ 14 years old;group 2, 15 to 44 years old;group 3, 44 to 64 years old;and group 4, ≥ 65 years old. An age-specific susceptible-exposed-symptomatic-asymptomatic-recovered/removed model was developed to estimate the transmissibility and simulate the optimal vaccination strategy. The effective reproduction number (R_(eff)) was used to estimate the transmission interaction in different age groups.Results: A total of 47 722 new cases were reported in Wuhan City from December 2, 2019, to March 16, 2020. Before the travel ban of Wuhan City, the highest transmissibility was observed among age group 2 (R_(eff) = 4.28), followed by group 2 to 3 (R_(eff) = 2.61), and group 2 to 4 (R_(eff) = 1.69). China should vaccinate at least 85% of the total population to interrupt transmission. The priority for controlling transmission should be to vaccinate 5% to 8% of individuals in age group 2 per day (ultimately vaccinated 90% of age group 2), followed by 10% of age group 3 per day (ultimately vaccinated 90% age group 3). However, the optimal vaccination strategy for reducing the disease severity identified individuals ≥ 65 years old as a priority group, followed by those 45-64 years old.Conclusions: Approximately 85% of the total population (nearly 1.2 billion people) should be vaccinated to build an immune barrier in China to safely consider removing border restrictions. Based on these results, we concluded that 90% of adults aged 15-64 years should first be vaccinated to prevent transmission in China.展开更多
This paper discusses the application of a pulse vaccination strategy to prevent and control some infectious diseases, which is described by age-structured SIR model in which susceptible and recovered individuals are s...This paper discusses the application of a pulse vaccination strategy to prevent and control some infectious diseases, which is described by age-structured SIR model in which susceptible and recovered individuals are structured by chronological age, while infected individuals are structured by infection age （duration since infection）. The time dependent disease-free equilibrium is determined, for which an explicit expression exists. The analytical results show that there exists a globally stable infectiomfree situation if the impulsive period T and proportion p satisfy Ro（p,T） 〈 1. Optimal problem is discussed： Pulse vaccination strategy with minimal costs at given R0（p, T） 〈 1.展开更多
The rational and effective implementation of epidemic prevention and control measures is crucial to controlling the spread of COVID-19, and vaccination is a key part to be considered in the development of epidemic pre...The rational and effective implementation of epidemic prevention and control measures is crucial to controlling the spread of COVID-19, and vaccination is a key part to be considered in the development of epidemic prevention and control strategies. In order to give full play to the greater role of vaccination strategies in epidemic prevention and control, more accurate and efficient vaccination strategies should be explored. Based on the classical SEIR dynamic model, this paper established a COVID-19 dynamic model of population age structure in the form of population grouping and combined with the transmission characteristics of the COVID-19 epidemic. An optimization model with the goal of minimizing daily infection was established to analyze the optimization studies on infection-related specificity of vaccination for different age groups under the condition of limited daily vaccine supply at the early stage of the epidemic, and to obtain the priority of vaccination strategies for Chinese age groups. And the effect of the heterogeneity of infection rate and hospitalization rate on the priority of vaccine allocation.展开更多
This study aimed to explore the barriers affecting COVID-19 vaccine uptake among ethnic minorities and to propose strategies to strengthen government initiatives for inclusive vaccination. Grounded in social construct...This study aimed to explore the barriers affecting COVID-19 vaccine uptake among ethnic minorities and to propose strategies to strengthen government initiatives for inclusive vaccination. Grounded in social constructivism, this qualitative study was conducted in the greater Sylhet Division, where many ethnic communities live. Using purposive sampling, semi-structured interviews were conducted with 49 participants, including ethnic men and women, community leaders, and healthcare providers. Two focus group discussions (FGDs) were also conducted to ensure data validation, and the results were analyzed using thematic analysis, which revealed several factors, such as free vaccinations, media, close community-knit healthcare centers, informal communication that positively influenced vaccine uptake, such as awareness campaigns, informal communication, media involvement, and free vaccine availability. However, socio-economic and technological barriers pose significant challenges, including misconceptions about vaccines, limited access to technology, long distances to vaccination centers, inconvenient service hours, and reliance on traditional medicine. To promote inclusive vaccination, the study recommends establishing localized vaccine camps, improving technological infrastructure such as the Internet and network access, enhancing communication strategies, providing special services for women, the elderly and disabled individuals, and ensuring a reliable vaccine supply. Future researchers could apply longitudinal studies, including a lager study area and broader range of participants to address the missing perspectives in the current study.展开更多
The World Health Organization(WHO)prioritizes pneumococcal disease as a vaccine-preventable disease and recommends the inclusion of pneumococcal conjugate vaccines(PCV)in national immunization programs worldwide.Howev...The World Health Organization(WHO)prioritizes pneumococcal disease as a vaccine-preventable disease and recommends the inclusion of pneumococcal conjugate vaccines(PCV)in national immunization programs worldwide.However,PCV is not included in the National Immunization Program in China and has low vaccination coverage due to its high cost.To address this,Weifang City implemented an innovative strategy for a 13-valent PCV(PCV13)on June 1,2021.This strategy aimed to provide one dose of PCV13 free of charge for children aged 6 months to 2 years in registered households and to adopt a commercial insurance model with one dose of PCV13 free of charge in 2023 for children over 2 years old.The Health Commission of Weifang and other departments conducted a comprehensive investigation and considered various factors,such as vaccine efectiveness,safety,accessibility,vaccine price,and immunization schedules,for eligible children(under 5 years old).Stakeholder opinions were also solicited before implementing the policy.The Commission negotiated with various vaccine manufacturers to maximize its negotiating power and reduce vaccine prices.The implementation plan was introduced under the Healthy Weifang Strategy.Following the implementation of this strategy,the full course of vaccination coverage increased signifcantly from 0.67 to 6.59%.However,vaccination coverage is still lower than that in developed countries.Weifang’s PCV13 vaccination innovative strategy is the frst of its kind in Chinese mainland and is an active pilot of non-immunization program vaccination strategies.To further promote PCV13 vaccination,Weifang City should continue to implement this strategy and explore appropriate fnancing channels.Regions with higher levels of economic development can innovate the implementation of vaccine programs,broaden fnancing channels,improve accessibility to vaccination services,and advocate for more localities to incorporate PCV13 into locally expanded immunization programs or people-benefting projects.A monitoring and evaluation system should also be established to evaluate implementation efects.展开更多
Vaccination has confirmed efficacy in preventing human papillomavirus(HPV)infection.The inclusion of males in vaccination programs remains a subject of debate,and the optimal allocation of vaccines across genders for ...Vaccination has confirmed efficacy in preventing human papillomavirus(HPV)infection.The inclusion of males in vaccination programs remains a subject of debate,and the optimal allocation of vaccines across genders for maximizing benefits remains unclear.This work proposes a heterosexual HPV transmission model with vaccination and employs the data from Xinjiang of China,as a case study to assess HPV vaccination strategies.The dynamics of the model,including the nonnegativity and boundedness of solutions,the calculation of the basic reproduction number(BRN),the stability of disease-free equilibrium,and the uniform persistence of disease,are investigated.Theoretical findings highlight the decisive role of the BRN in determining model dynamics.Furthermore,the optimal vaccine distribution strategy between males and females was established when the vaccine amount is limited.Meanwhile,this work involves fitting and estimating parameters and the current BRN based on actual data regarding with HPV infection and secondary cervical cancer(CC)cases in Xinjiang from January 2009 to December 2019.The numerical simulations are employed to explore the sensitivity of model parameters,especially the vaccination rates,to the BRN and HPV infection and CC with time changes,discuss the impact of vaccine distribution between males and females on the dynamic changes in new cases of HPV infection and CC,and further analyzed the control effect of bivalent and nine-valent HPV vaccines in Xinjiang of China.Additionally,several practical strategies are introduced to manage the continued spread of HPV infection and CC in the region.展开更多
As public health policies shifted in 2023 from emergency response to long-term COVID-19 disease management,immunization programs started to face the challenge of formulating routine booster campaigns in a still highly...As public health policies shifted in 2023 from emergency response to long-term COVID-19 disease management,immunization programs started to face the challenge of formulating routine booster campaigns in a still highly uncertain seasonal behavior of the COVID-19 epidemic.Mathematical models assessing past booster campaigns and integrating knowledge on waning of immunity can help better inform current and future vaccination programs.Focusing on the first booster campaign in the 2021/2022 winter in France,we used a multi-strain age-stratified transmission model to assess the effectiveness of the observed booster vaccination in controlling the succession of Delta,Omicron BA.1 and BA.2 waves.We explored counterfactual scenarios altering the eligibility criteria and inter-dose delay.Our study showed that the success of the immunization program in curtailing the Omicron BA.1 and BA.2 waves was largely dependent on the inclusion of adults among the eligible groups,and was highly sensitive to the inter-dose delay,which was changed over time.Shortening or prolonging this delay,even by only one month,would have required substantial social distancing interventions to curtail the hospitalization peak.Also,the time window for adjusting the delay was very short.Our findings highlight the importance of readiness and adaptation in the formulation of routine booster campaign in the current level of epidemiological uncertainty.展开更多
To mitigate casualties from the COVID-19 outbreak,this study aims at assessing the optimal vaccination scenarios,considering several existing healthcare conditions and assumptions,by developing SIQRD(Susceptible-Infec...To mitigate casualties from the COVID-19 outbreak,this study aims at assessing the optimal vaccination scenarios,considering several existing healthcare conditions and assumptions,by developing SIQRD(Susceptible-Infected-Quarantine-Recovery-Death)models for Jakarta,West Java,and Banten,in Indonesia.The models include an age-structured dynamic transmission model that naturally allows for different treatments among different age groups of the population.The simulation results show that the timing and period of the vaccination should be well planned and prioritizing particular age groups will give a significant impact on the total number of casualties.展开更多
In this paper, based on a class of multi-group epidemic models of SEIR type with bilinear incidences, we introduce a vaccination compartment, leading to multi-group SVEIR model. We establish that the global dynamics a...In this paper, based on a class of multi-group epidemic models of SEIR type with bilinear incidences, we introduce a vaccination compartment, leading to multi-group SVEIR model. We establish that the global dynamics are completely determined by the basic reproduction number R0V which is defined by the spectral radius of the next generation matrix. Our proofs of global stability of the equilibria utilize a graph-theoretical approach to the method of Lyapunov functionals. Mathematical results suggest that vaccination is helpful for disease control by decreasing the basic reproduction number. However, there is a necessary condition for successful elimination of disease. If the time for the vaccines to obtain immunity or the possibility for them to be infected before acquiring immunity is neglected in each group, this condition will be satisfied and the disease can always be eradicated by suitable vaccination strategies. This may lead to over evaluation for the effect of vaccination.展开更多
This article focuses on the study of an age structured SEIRS epidemic model with a vaccination program when the total population size is not kept at constant. We first give the explicit expression of the reproduction ...This article focuses on the study of an age structured SEIRS epidemic model with a vaccination program when the total population size is not kept at constant. We first give the explicit expression of the reproduction number in the presence of vaccine ( is the exponent of growth of total population), and show that the infection-free steady state is linearly stable if and unstable if , then we apply the theoretical results to vaccination policies to determine the optimal age or ages at which an individual should be vaccinated. It is shown that the optimal strategy can be either one- or two-age strategies.展开更多
The immune imprinting against SARS-CoV-2 subvariants that dynamically evolves through sequential vaccination and infection has been rarely studied.Using antigenic cartography and neutralizing antibody(NAb)profiling,we...The immune imprinting against SARS-CoV-2 subvariants that dynamically evolves through sequential vaccination and infection has been rarely studied.Using antigenic cartography and neutralizing antibody(NAb)profiling,we demonstrate that prototypetargeting vaccination followed by Delta/early Omicron breakthrough infections maintained dominant wild-type(WT)-focused immunity.However,XBB.1.5-adapted vaccination after BA.5 outbreaks shifted immune imprinting toward XBB.1.9.1,altering the antigenic landscape.NAb analysis revealed progressive WT-specific immunity enhancement through three-dose vaccination followed by BA.5 breakthrough infection(GMT:I-I=35,I-I-I=72,I-I-I-B5=807),followed by sharp decline after XBB reinfection(GMT:I-I-I-B5-XBB=231),confirming XBB’s antigenic divergence.To investigate the relationship between population immune dynamics and XBB infection risk following the BA.5/BF.7 wave,we analyzed the immune status of XBB breakthrough-infected and uninfected individuals from May to June 2023(5–7 months post-wave).Utilizing an infection model calibrated to NAb titers against XBB.1.9.1,we estimated the 50%protective NAb titer against XBB infection to be 1:12.6.Retrospective analysis revealed that 80.3%of the population fell below this threshold in mid-2023,aligning with subsequent XBB resurgence.However,only 33.8%exhibited sub-protective JN.1 titers(<12.6)by August 2024,explaining the absence of JN.1-driven endemicity.This longitudinal study maps the immune imprint transitions from WT dominance to XBB adaptation,providing critical insights into vaccine strategy optimization and emerging variant risk assessment.The work highlights how iterative immune exposures reshape population protection landscapes against evolving coronaviruses.展开更多
基金the Bill&Melinda Gates Foundation(Grant INV-005834 to T.C.)the Science and Technology Program of Fujian Province(Grant 2020Y0002 to T.C.)NHC Key Laboratory of Echinococcosis Preven‑tion and Control(Grant 2020WZK2001 to T.C.)。
文摘Background: Reaching optimal vaccination rates is an essential public health strategy to control the coronavirus disease 2019 (COVID-19) pandemic. This study aimed to simulate the optimal vaccination strategy to control the disease by developing an age-specific model based on the current transmission patterns of COVID-19 in Wuhan City, China.Methods: We collected two indicators of COVID-19, including illness onset data and age of confirmed case in Wuhan City, from December 2, 2019, to March 16, 2020. The reported cases were divided into four age groups: group 1, ≤ 14 years old;group 2, 15 to 44 years old;group 3, 44 to 64 years old;and group 4, ≥ 65 years old. An age-specific susceptible-exposed-symptomatic-asymptomatic-recovered/removed model was developed to estimate the transmissibility and simulate the optimal vaccination strategy. The effective reproduction number (R_(eff)) was used to estimate the transmission interaction in different age groups.Results: A total of 47 722 new cases were reported in Wuhan City from December 2, 2019, to March 16, 2020. Before the travel ban of Wuhan City, the highest transmissibility was observed among age group 2 (R_(eff) = 4.28), followed by group 2 to 3 (R_(eff) = 2.61), and group 2 to 4 (R_(eff) = 1.69). China should vaccinate at least 85% of the total population to interrupt transmission. The priority for controlling transmission should be to vaccinate 5% to 8% of individuals in age group 2 per day (ultimately vaccinated 90% of age group 2), followed by 10% of age group 3 per day (ultimately vaccinated 90% age group 3). However, the optimal vaccination strategy for reducing the disease severity identified individuals ≥ 65 years old as a priority group, followed by those 45-64 years old.Conclusions: Approximately 85% of the total population (nearly 1.2 billion people) should be vaccinated to build an immune barrier in China to safely consider removing border restrictions. Based on these results, we concluded that 90% of adults aged 15-64 years should first be vaccinated to prevent transmission in China.
基金supported by Natural Science Foundation of Henan Province under Grant No.092300410206Science and Technology Program of Educational Department of Henan Province under Grant No. 2009A110015
文摘This paper discusses the application of a pulse vaccination strategy to prevent and control some infectious diseases, which is described by age-structured SIR model in which susceptible and recovered individuals are structured by chronological age, while infected individuals are structured by infection age （duration since infection）. The time dependent disease-free equilibrium is determined, for which an explicit expression exists. The analytical results show that there exists a globally stable infectiomfree situation if the impulsive period T and proportion p satisfy Ro（p,T） 〈 1. Optimal problem is discussed： Pulse vaccination strategy with minimal costs at given R0（p, T） 〈 1.
文摘The rational and effective implementation of epidemic prevention and control measures is crucial to controlling the spread of COVID-19, and vaccination is a key part to be considered in the development of epidemic prevention and control strategies. In order to give full play to the greater role of vaccination strategies in epidemic prevention and control, more accurate and efficient vaccination strategies should be explored. Based on the classical SEIR dynamic model, this paper established a COVID-19 dynamic model of population age structure in the form of population grouping and combined with the transmission characteristics of the COVID-19 epidemic. An optimization model with the goal of minimizing daily infection was established to analyze the optimization studies on infection-related specificity of vaccination for different age groups under the condition of limited daily vaccine supply at the early stage of the epidemic, and to obtain the priority of vaccination strategies for Chinese age groups. And the effect of the heterogeneity of infection rate and hospitalization rate on the priority of vaccine allocation.
文摘This study aimed to explore the barriers affecting COVID-19 vaccine uptake among ethnic minorities and to propose strategies to strengthen government initiatives for inclusive vaccination. Grounded in social constructivism, this qualitative study was conducted in the greater Sylhet Division, where many ethnic communities live. Using purposive sampling, semi-structured interviews were conducted with 49 participants, including ethnic men and women, community leaders, and healthcare providers. Two focus group discussions (FGDs) were also conducted to ensure data validation, and the results were analyzed using thematic analysis, which revealed several factors, such as free vaccinations, media, close community-knit healthcare centers, informal communication that positively influenced vaccine uptake, such as awareness campaigns, informal communication, media involvement, and free vaccine availability. However, socio-economic and technological barriers pose significant challenges, including misconceptions about vaccines, limited access to technology, long distances to vaccination centers, inconvenient service hours, and reliance on traditional medicine. To promote inclusive vaccination, the study recommends establishing localized vaccine camps, improving technological infrastructure such as the Internet and network access, enhancing communication strategies, providing special services for women, the elderly and disabled individuals, and ensuring a reliable vaccine supply. Future researchers could apply longitudinal studies, including a lager study area and broader range of participants to address the missing perspectives in the current study.
基金supported by Bill and Melinda Gates Foundation(OPP1216666)Natural Science Foundation of Shandong Province(ZR2022MG032)+1 种基金Key R&D Program of Shandong Province,China(2023RKY07003)the research“Innovation Lab of Vaccine Delivery Research,”supported by the Bill&Melinda Gates Foundation(INV034554).
文摘The World Health Organization(WHO)prioritizes pneumococcal disease as a vaccine-preventable disease and recommends the inclusion of pneumococcal conjugate vaccines(PCV)in national immunization programs worldwide.However,PCV is not included in the National Immunization Program in China and has low vaccination coverage due to its high cost.To address this,Weifang City implemented an innovative strategy for a 13-valent PCV(PCV13)on June 1,2021.This strategy aimed to provide one dose of PCV13 free of charge for children aged 6 months to 2 years in registered households and to adopt a commercial insurance model with one dose of PCV13 free of charge in 2023 for children over 2 years old.The Health Commission of Weifang and other departments conducted a comprehensive investigation and considered various factors,such as vaccine efectiveness,safety,accessibility,vaccine price,and immunization schedules,for eligible children(under 5 years old).Stakeholder opinions were also solicited before implementing the policy.The Commission negotiated with various vaccine manufacturers to maximize its negotiating power and reduce vaccine prices.The implementation plan was introduced under the Healthy Weifang Strategy.Following the implementation of this strategy,the full course of vaccination coverage increased signifcantly from 0.67 to 6.59%.However,vaccination coverage is still lower than that in developed countries.Weifang’s PCV13 vaccination innovative strategy is the frst of its kind in Chinese mainland and is an active pilot of non-immunization program vaccination strategies.To further promote PCV13 vaccination,Weifang City should continue to implement this strategy and explore appropriate fnancing channels.Regions with higher levels of economic development can innovate the implementation of vaccine programs,broaden fnancing channels,improve accessibility to vaccination services,and advocate for more localities to incorporate PCV13 into locally expanded immunization programs or people-benefting projects.A monitoring and evaluation system should also be established to evaluate implementation efects.
基金supported by the Project of“Tianshan Talent”Trainning Program in Xinjiang,China(Grant No.2024TSYCCX0081)the National Natural Science Foundation of China(Grant Nos.12101529,12371504).
文摘Vaccination has confirmed efficacy in preventing human papillomavirus(HPV)infection.The inclusion of males in vaccination programs remains a subject of debate,and the optimal allocation of vaccines across genders for maximizing benefits remains unclear.This work proposes a heterosexual HPV transmission model with vaccination and employs the data from Xinjiang of China,as a case study to assess HPV vaccination strategies.The dynamics of the model,including the nonnegativity and boundedness of solutions,the calculation of the basic reproduction number(BRN),the stability of disease-free equilibrium,and the uniform persistence of disease,are investigated.Theoretical findings highlight the decisive role of the BRN in determining model dynamics.Furthermore,the optimal vaccine distribution strategy between males and females was established when the vaccine amount is limited.Meanwhile,this work involves fitting and estimating parameters and the current BRN based on actual data regarding with HPV infection and secondary cervical cancer(CC)cases in Xinjiang from January 2009 to December 2019.The numerical simulations are employed to explore the sensitivity of model parameters,especially the vaccination rates,to the BRN and HPV infection and CC with time changes,discuss the impact of vaccine distribution between males and females on the dynamic changes in new cases of HPV infection and CC,and further analyzed the control effect of bivalent and nine-valent HPV vaccines in Xinjiang of China.Additionally,several practical strategies are introduced to manage the continued spread of HPV infection and CC in the region.
基金funded by:Agence Nationale de la Recherche project DATAREDUX(ANR-19-CE46-0008-03)to VCANRSeMaladies InfectieusesEmergentes project EMERGEN(ANRS0151)to VC+2 种基金Horizon Europe grant ESCAPE(101095619)to VCEU HORIZON grant VERDI(101045989)EU Horizon 2020 grant MOOD(H2020-874850)to VC.The study is catalogued as MOOD105。
文摘As public health policies shifted in 2023 from emergency response to long-term COVID-19 disease management,immunization programs started to face the challenge of formulating routine booster campaigns in a still highly uncertain seasonal behavior of the COVID-19 epidemic.Mathematical models assessing past booster campaigns and integrating knowledge on waning of immunity can help better inform current and future vaccination programs.Focusing on the first booster campaign in the 2021/2022 winter in France,we used a multi-strain age-stratified transmission model to assess the effectiveness of the observed booster vaccination in controlling the succession of Delta,Omicron BA.1 and BA.2 waves.We explored counterfactual scenarios altering the eligibility criteria and inter-dose delay.Our study showed that the success of the immunization program in curtailing the Omicron BA.1 and BA.2 waves was largely dependent on the inclusion of adults among the eligible groups,and was highly sensitive to the inter-dose delay,which was changed over time.Shortening or prolonging this delay,even by only one month,would have required substantial social distancing interventions to curtail the hospitalization peak.Also,the time window for adjusting the delay was very short.Our findings highlight the importance of readiness and adaptation in the formulation of routine booster campaign in the current level of epidemiological uncertainty.
基金NN and KKS gratefully acknowledges the financial support provided by PDUPT 2021.
文摘To mitigate casualties from the COVID-19 outbreak,this study aims at assessing the optimal vaccination scenarios,considering several existing healthcare conditions and assumptions,by developing SIQRD(Susceptible-Infected-Quarantine-Recovery-Death)models for Jakarta,West Java,and Banten,in Indonesia.The models include an age-structured dynamic transmission model that naturally allows for different treatments among different age groups of the population.The simulation results show that the timing and period of the vaccination should be well planned and prioritizing particular age groups will give a significant impact on the total number of casualties.
文摘In this paper, based on a class of multi-group epidemic models of SEIR type with bilinear incidences, we introduce a vaccination compartment, leading to multi-group SVEIR model. We establish that the global dynamics are completely determined by the basic reproduction number R0V which is defined by the spectral radius of the next generation matrix. Our proofs of global stability of the equilibria utilize a graph-theoretical approach to the method of Lyapunov functionals. Mathematical results suggest that vaccination is helpful for disease control by decreasing the basic reproduction number. However, there is a necessary condition for successful elimination of disease. If the time for the vaccines to obtain immunity or the possibility for them to be infected before acquiring immunity is neglected in each group, this condition will be satisfied and the disease can always be eradicated by suitable vaccination strategies. This may lead to over evaluation for the effect of vaccination.
基金Supported by the NSFC (No.10371105) and the NSF of Henan Province (No.0312002000No.0211044800)
文摘This article focuses on the study of an age structured SEIRS epidemic model with a vaccination program when the total population size is not kept at constant. We first give the explicit expression of the reproduction number in the presence of vaccine ( is the exponent of growth of total population), and show that the infection-free steady state is linearly stable if and unstable if , then we apply the theoretical results to vaccination policies to determine the optimal age or ages at which an individual should be vaccinated. It is shown that the optimal strategy can be either one- or two-age strategies.
基金supported by the National Key Research and Development Program of China(2022YFC2604104)the National Natural Science Foundation of China(grant numbers 81971485)+2 种基金R&D Program of Guangzhou National Laboratory(SRPG23-005)S&T Program of Guangzhou Laboratory(SRPG22-006)the grant of State Key Laboratory of Respiratory Disease(SKLRD-Z-202220).
文摘The immune imprinting against SARS-CoV-2 subvariants that dynamically evolves through sequential vaccination and infection has been rarely studied.Using antigenic cartography and neutralizing antibody(NAb)profiling,we demonstrate that prototypetargeting vaccination followed by Delta/early Omicron breakthrough infections maintained dominant wild-type(WT)-focused immunity.However,XBB.1.5-adapted vaccination after BA.5 outbreaks shifted immune imprinting toward XBB.1.9.1,altering the antigenic landscape.NAb analysis revealed progressive WT-specific immunity enhancement through three-dose vaccination followed by BA.5 breakthrough infection(GMT:I-I=35,I-I-I=72,I-I-I-B5=807),followed by sharp decline after XBB reinfection(GMT:I-I-I-B5-XBB=231),confirming XBB’s antigenic divergence.To investigate the relationship between population immune dynamics and XBB infection risk following the BA.5/BF.7 wave,we analyzed the immune status of XBB breakthrough-infected and uninfected individuals from May to June 2023(5–7 months post-wave).Utilizing an infection model calibrated to NAb titers against XBB.1.9.1,we estimated the 50%protective NAb titer against XBB infection to be 1:12.6.Retrospective analysis revealed that 80.3%of the population fell below this threshold in mid-2023,aligning with subsequent XBB resurgence.However,only 33.8%exhibited sub-protective JN.1 titers(<12.6)by August 2024,explaining the absence of JN.1-driven endemicity.This longitudinal study maps the immune imprint transitions from WT dominance to XBB adaptation,providing critical insights into vaccine strategy optimization and emerging variant risk assessment.The work highlights how iterative immune exposures reshape population protection landscapes against evolving coronaviruses.
