Study On The Effectiveness Evaluation Of Influenza Vaccination For Schoo-age Children In Beijing

BackgroundSeasonal influenza is one of the most common acute respiratory infectious diseases caused by influenza virus,which is also a notifiable infectious disease in China.Annually,influenza affects an estimated 5%to 10%of adults and 20%to 30%of children,causing over 290 thousand deaths worldwide every year,and resulting in a significant global health and economic burden.Primary and secondary schools are frequently affected by influenza febrile outbreaks in China,which is easy to cause social panic.Influenza vaccination is recommended by the World Health Organization(WHO)and several countries/regions to prevent influenza infection and reduce its severe outcomes.however,the vaccination effectiveness of influenza will be reduced due to the prone to mutation of the influenza virus.Therefore,it is generally necessary to evaluate the effect of influenza vaccine every year.Since 2007,a school-based influenza vaccination program has been implemented in Beijing,in which inactive influenza vaccine(??)has been provided to primary and secondary school students at no charge to families.Under the school-based influenza vaccination program,a systematic evaluation of the vaccination effectiveness for school-age children was needed.ObjectivesTo explore the epidemiological characteristics of influenza among school-age children in Beijing and to evaluate the vaccination effectiveness of free influenza vaccination on individual school-age children and the prevention effect of influenza outbreaks.to quantitatively evaluate the impact of current influenza vaccination program on the incidence of influenza in school-age children by building ARIMAX and age-structed transmission dynamic model.MethodsWe collected influenza data from the 27th week of 2017 to the 26th week of 2020,which included 3 influenza seasons.The sources of data were from:Influenza-like illness Surveillance System,Influenza Etiology Surveillance System,Febrile illness outbreak surveillance system,and Immune Planning Information Management System.Based on case control study design,we compared influenza and non-influenza to analyze the protective effect of influenza vaccine on individual children based on the hospital outpatient situation and the influenza outbreak situation.Comparing schools with influenza outbreaks and schools without influenza outbreaks,analyze the preventive effects of influenza vaccines on influenza outbreaks;compare the different scales of influenza outbreaks and analyze the preventive effects of influenza vaccines on the scale of influenza outbreaks.The Monte Carlo multiplication model is used to estimate the actual number of influenza infections.Use this data,we build ARIMAX model and age-structed transmission dynamic model to estimate the reduction of influenza caused by the current vaccination program.Results1.In the three influenza epidemic seasons from 2017 to 2020,the influenza vaccine had a higher protective effect(45.0%,P<0.05)based on influenza outbreaks,and the trend was similar in every influenza epidemic season and in each subtype/lineage.While the influenza vaccine had a low protective effect(1.6%)on school-age children,based on hospital outpatient clinics.2.In the 2017/2018 epidemic season and the 2018/2019 epidemic season,higher school vaccination coverage reduced influenza outbreaks by 37%and 50%,respectively.No such association was found in the 2019/2020 epidemic season.The multi-stage regression model showed that the optimal school influenza vaccination coverage in the three influenza epidemic seasons were?65%,?51%,and?69%,respectively.Due to timely response to the influenza outbreak,no correlation between influenza vaccination and the scale of outbreaks could be found.3.Estimated by the Monte Carlo multiplication model,the actual number of influenza in the 5-14-year-old group is about 9.2 times the number of reported influenza cases,and the incidence rate was 30.15%.Using the ARIMAX model,it was estimated that the current vaccination program could prevent 8.75%of influenza aged 5-14.Using the age-structured SEIR+v model,the basic reproductive number(R0)in aged 5-14 children was 1.75.Under the current vaccination program,it was estimated that 508569 cases in 5-14-year-old group were prevented from influenza infection and 55040 cases in 5-14-year-old group were avoided to visit hospitals in the three epidemic seasons.Besides,due to the external effect of the vaccine,it was estimated that 538815.07 cases in other age groups were prevented from influenza infection and 58313.3 cases were avoided to visit hospitals.ConclusionsIn the three epidemic seasons from 2017/2018 to 2019/2020,influenza vaccine had a low protective effect on school-age children,based on hospital outpatient clinics.,however,it had a higher protection effect based on influenza outbreaks.High vaccination coverage in school could prevent influenza outbreaks.Influenza vaccination program for school-age children in Beijing has significantly improved the vaccination coverage of children,resulting in herd immunization among school-age children.The program not only protects school-age children from influenza,but also prevents a mass of people in other age groups from influenza due to the external effect of the vaccine.Besides,to better prevent annual influenza,further increase influenza vaccination of school-age children should be put in a priority position.AdviseThe school-based influenza vaccination program should continue to be implement.We should continue to implement school-based influenza vaccination program in Beijing.At the same time,we should further improve vaccination coverage of school-age children,so that influenza vaccination could play a more important role to prevent influenza.According to the results of this study,the cost-benefit evaluation of school-based influenza vaccination program should be carried out to provide health economic evidence for further promoting the free influenza vaccination policy for school-age children.