Protective Effectiveness Of The Enterovirus 71 Vaccine On Enterovirus 71 Asscociated Hand,foot And Mouth Disease

Objective:Enterovirus 71(EV71)is one of the main pathogens of hand,foot and mouth disease(HFMD).EV71 associated HFMD cases often suffered from serious clinical manifestations.The EV71 vaccine was launched in Guangdong Province in August 2016.However,the protective effectiveness of the EV71 vaccine in the real world is still unclear.This study intends to evaluate the protective effectiveness of the EV71 vaccine measures against EV71 HFMD in the population,and to further explore its effectiveness under different vaccination rates by constructing a dynamic model of HFMD caused by EV71 infection in people aged 5 and under in Guangdong Province.The results of our research are expected to provide scientific basis for the prevention and control of hand,foot and mouth disease and the implementation of EV71 vaccination strategies.Methods:(1)Collecting the case data of hand,foot and mouth disease in Guangdong Province from 2012 to 2019,the pathogenic surveillance data of hand,foot and mouth disease,and the EV71 vaccination data of Guangdong Province from 2017 to 2019,then describing the epidemic of hand,foot and mouth disease caused by EV71 infection in Guangdong Province caused by the year-on-year increase in the vaccination rate after the EV71 vaccine was launched.Changes in trends and their temporal and spatial distribution characteristics.(2)Combined with the seasonal and periodic prevalence of hand,foot and mouth disease caused by EV71 infection in people aged 5 years and under in Guangdong Province,establish the corresponding dynamic model by the theory of infectious disease dynamics and the warehouse model method;query through literature as well as model fitting and other methods to obtain model parameters,R2 and root mean square error(RMSE)were used to evaluate the accuracy of model fitting;Bayesian structure time series model was applied to calculate the key parameters of the model(seasonal infection coefficient),using model counterfactuals to predict the incidence of the EV71 vaccine from2017 to 2019 when the EV71 vaccine is not vaccinated,and evaluates the vaccine protection effect under the current EV71 vaccination rate by calculating the reduction ratio of the actual number of cases in each year to the predicted number of cases.(3)Introduce vaccination into the constructed model to simulate the incidence of EV71 hand-foot-mouth disease in people aged 5 and under in Guangdong Province under different vaccination rates.Results:(1)After the EV71 vaccine programme in 2017,the positive rate of EV71 in Guangdong Province has been declining year by year,dropping to 0.26% in 2019.Compared with 2012～2016,the average number of EV71 infections of hand,foot and mouth disease among people aged 5 and under in Guangdong Province from 2017 to 2019 decreased by 79.82%,and the annual average number of severe cases of EV71 infection(including death cases)decreased by 85.24%.From a spatial point of view,the average annual EV71 infection rate in various cities in Guangdong Province has dropped by 72.68%compared to when it was not vaccinated.(2)The kinetic model of hand,foot and mouth disease caused by EV71 infection in people aged 5 years and under in Guangdong Province was used to fit the incidence data from 2013 to 2016 year by year,and the accuracy of the model was high.The counterfactual prediction results of the kinetic model show that the EV71 vaccine prevented 460,137(95% confidence interval:135,477～716,336)cases of EV71 hand-foot-mouth disease between 2017 and 2019,and the overall protective effect of the vaccine for three years was 88.25%(95% confidence Interval: 68.86%～92.12%).(3)When the EV71 vaccination rate is maintained at more than40% and the duration is more than 2 years,the EV71-associated hand,foot and mouth disease can no longer be prevalent.Conclusions:After Guangdong Province launched the EV71 vaccination plan,the number of cases of hand,foot and mouth disease caused by EV71 infection in people aged 5 years and under in Guangdong Province has dropped significantly.The result showed that EV71 vaccination has an important protective effectiveness in the age group.In order to effectively control the spread and prevalence of this type of hand,foot and mouth disease,the EV71 vaccination rate should be controlled above 40%.