Research On The Strategy Of Supplementary Immunization To Eliminate Measles And Rubella In My Country

BackgroundMeasles and rubella are both vaccine preventable acute respiratory infectious disease.Considering children’s sufferings from measles and catastrophic result of rubella infection during pregnancy,as well as driving effort on improvement of immunization program and service quality,China and the whole world are working towards measles and rubella elimination.However,in recent years,China faced measles resurge,rubella outbreaks and challenges about achieving elimination goals.ObjectivesAnalyze epidemiological profile and immunity level of measles and rubella in China,analyze optimal supplementary immunization strategy to achieve measles and rubella elimination,assess the feasibility and economic value of supplementary immunization strategy.To comprehensively assess the optimal supplementary immunization strategy from aspects of effectiveness,feasibility and cost-benefit.Methods1.Analyzing measles and rubella disease pattern and susceptible profile from measles surveillance and serological survey.2.Based on data from surveillance,serological survey,demographic data,and vaccine,usage history and coverage,develop measles and rubella dynamic transmission model with age and location structure;to calculate basic reproduction number;estimate rubella outbreak possibility and CRS number;use Gradient method,combined with simulation,to analyze optimal supplementary immunization strategy3.Assess supplementary immunization target group’s and related departments’ acceptance and influential factors,using questionnaire and focus group discussion method.4.Evaluate economic value of supplementary immunization strategy,through collecting cost of disease,surveillance and outbreak response,estimating cost of supplementary immunization.Based on two scenario,one is keeping only routine immunization,another is adding supplementary immunization,to calculate incremental cost-benefit ratio.Results1.Analysis of epidemiological characteristics and population immunity levels:Measles occurred in<2 years of age and adult,secondary school students constituted the main cases of rubella,outbreaks of measles and rubella occurred frequently in recent years.The incidence of both diseases fell to the lowest level in 2017(0.44 per 100,000 and 0.12 per 100,000).The positive rate of measles antibody in the 1 to 29-year-olds in China was 91.0%.Among them,95.8%of people aged 1 to 4 years old,93.6%of people aged 5 to 14 years old,and 88.9%of people aged 15 to 29 years old.There was a statistically significant difference among age groups.The positive rate of rubella antibody in Chinese people aged 1-29 years is 87.1%.Among them,92.7%were between 1 and 4 years old;82.1%were between 5 and 14 years old;88.3%were between 15 and 29 years old.The difference in the rates of the three age groups was statistically significant.The measles immunity of school-age children has not yet reached the level of blocking transmission.The overall measles immunization level in adults is low,and the level of rubella in people aged 5 to 14 years is low,with the risk of potential CRS.2.Dynamic transmission model:The measles basic reproduction number in China is 18,and the measles effective reproduction number in 2014 is 2.3;the rubella basic reproduction number is 7.6,and the effective rubella reproduction number in 2014 is 1.2.The results of stochastic model simulations show that the possibility of an outbreak of rubella in China at present is 20-60%and the number of CRS is estimated to be 348 cases(139-529 cases).It is necessary to fill the gap of immunity of middle school students early to avoid outbreak of rubella,which will result in increase in the risk of CRS.Gradient showed that for rubella,the best supplementary immunization target is middle school students.Although best target of measles gradient was not middle school students,but young adults,increasing the vaccine coverage in middle school students will also reduce measles effective reproduction number.The results of model simulations confirmed that MR vaccination for 10 to 14 years old and 15 to 19 years old(first grade of junior and senior middle school)from 2018 to 2020 for three consecutive years,if the vaccination coverage in susceptible ≥50%,incidence of measles can be reduced to<1/1 million within 5 years(the first year is 2019).For rubella,if the vaccination coverage in susceptible≥30%,and the incidence of rubella fell to<1/1 million within 3 years.The role of secondary school supplementary immunization to accelerate the elimination of measles and rubella is mainly reflected in the indirect protection of immunization.By establishing a higher level of herd immune in middle school students,the risk of infection in adults will be reduced,which will result in overall disease reduction.3.Investigation of the feasibility of secondary school replanting:Surveys were conducted in 2 cities of Henan,Shandong,Jiangsu and Xinjiang respectively.A total of 16 junior high schools(2298 students)and 16 high schools(2030 students,8 of which were vocational high schools)were investigated.The proportion of students keeping immunization certificate was 53.7%in junior high schools and 40.0%in high schools.Through three routes of getting immunization history information,which were immunization certificate,information system or vaccination card,the proportion of students’immunization history can be obtained is 75.5%for junior high school students and 63.3%for high school students.The proportion varies greatly among provinces.All of Shandong junior high school students can inquire into immunization history,but only 15 to 20%of Henan junior high school students and senior high school students can find it;within the province,the proportion is also different between junior high school students and high school students.Such as junior high school students in Jiangsu 96.7%access to information on immunization history,but 21.7%of high school students can’t find this information.The history of two doses of measles-containing vaccines and one dose of rubella-containing vaccines were considered as fully vaccinated,and this proportion was 65.1%,of which 70.5%were in junior high schools and 58%in high schools.If-students were fully vaccinated,73.0%of the parents accepted revaccination,and 83.3%of parents indicated revaccination was accepted if immunization was not completed.Interviews with school administrators and grass-roots health department personnel through focus group interviews showed that,both parties supported the measles and rubella supplementation immunization,and they prefer the first-grade students for immunization.The communication and social-mobilization,as well as staffing and funding guarantee are important.4.Economic evaluation of secondary school supplementation immunization:estimate the incidence of measles and rubella in the whole population based on the measles and rubella SEIR model with or without supplementary immunization and giving different coverage rates.Cost of measles and rubella diseases,investigations,and outbreak response was collected from field According to the discount rate of 3%,the cost of carrying out supplemental immunization activities for three consecutive years,the costs associated with the occurrence of diseases in the next six years were discounted according to 2018.If supplementary immunization activities are caried out based on vaccination history,when the coverage in susceptible was 30%,the cost is 2.03 million RMB,the incremental cost-benefit ratio was 4.62,the net value is 408 million,and if the non-selective supplementary immunization is carried out,the incremental cost-benefit ratio is 1.65.This supplemental immunization activity is cost-saving.Accelerating the elimination of measles and rubella can save social resources.ConclusionThe distribution characteristics of measles and rubella cases in China and the immunity level in the population show that the measles and rubella immunity level have not yet reached the level of interrupting measles and rubella virus circulation.It is necessary to develop effective supplementary immunization strategies to fill the immune gaps in key populations.Carrying measles and rubella supplementation immunization activity in middle school students will accelerate the elimination of measles and rubella.The acceptance by students and parents of junior high school and high school is relatively high.The proportion of students who can get information of vaccination history is generally high,but there are significant differences between provinces and within the province.Based on vaccination history can help with targeting more accurately,which is a more acceptable approach for parents.It is cost-effective to carry out secondary school reseeding,and the ICBR of selective vaccination is better than non-selective revaccination.