Prevalence Of And Vaccination Effectiveness Against Influenza A(H1N1) Virus Infection In Yangpu Populations

Objective:The prevalence of anti-H1N1of type-A epidemic influenza virus among the population in Yangpu district, Shanghai has been determined, and the contrast of effectiveness of the vaccine for influenza A (H1N1) virus versus that for seasonal influenza has been undertaken.Methods:A stratified multiple-stage cluster sampling strategy has been used.1500individuals have been enrolled from11communities in Yangpu district. All have been interviewed through questionnaires and their blood samples have been collected for serological tests on the anti-HlNl against influenza A virus (H1N1). Those whose titers of hemagglutination-inhibition antibody reach above1:40have been considered as being effectively vaccinated. At the same time, the cases who meet with clinical criteria of influenza-like illness or fever have been collected from all the middle and elementary schools in Yangpu District. A database has been set up and statistical analysis has been done by SPSS software (version16.0).Results:1. Prevalence of anti-H1N1of type-A epidemic influenza virus infection:①Out of the1500participants enrolled,721individuals have been tested with a positive result of anti-H1N1against type-A epidemic influenza virus with a proportion of48.07%. Out of721with positive anti-H1N1,30.53%are considered as being effectively vaccinated, either by the vaccination or through natural infection.②Out of the1500participants enrolled,28.93%(434cases) have received the vaccine against type-A influenza virus (H1N1).③The prevalence of anti-H1N1against type-A epidemic influenza virus is the highest among those aged6-15years old but the lowest among those aged above60years old.④The prevalence of anti-H1N1against type-A epidemic influenza virus is higher among those who have received the vaccine than those who have not.⑤The prevalence of anti-H1N1against type-A epidemic influenza virus is the highest among the students but the lowest among those kindergarten children.⑥The prevalence of anti-H1N1against type-A epidemic influenza virus is higher among the male than the female.⑦The ratio of the overt infection versus the occult is2.04:1.2. The efficacy of the vaccine against influenza A (H1N1) virus or seasonal influenza.①This study has enrolled62,978students from the106schools in11communities in Yangpu District, including53schools each from the elementary and middle level.②The proportions of vaccination for the vaccine against influenza A (H1N1) virus and seasonal influenza are respectively54.93%and46.35%for the students from the elementary schools, and44.54%and28.62%for those from the middle schools.③The incidence of influenza-like illness or fever cases has dropped to the lowest in February,2010but risen to its peaked in September,2009.④The incidence proportion of fever cases is the highest in Jiangpu Community but the lowest in Daqiao.⑤The incidence proportion of influenza-like illness cases is the highest in Changbai Community but the lowest in Yinhang.⑥The protection rate of the vaccine against influenza A (H1N1) virus on fever cases and influenza-like illness is respectively91.80%and81.65%.⑦The protection rate of the vaccine against seasonal influenza vaccine on fever cases and influenza-like illness is respectively84.09%and84.95%.Discussion:①More occult cases infected with influenza A (H1N1) virus have been identified, which implies that there exists a tendency for the spread of the epidemic.②The vaccination with the vaccine against influenza A (H1N1) virus will provide a good protection for the cases either with fever cases or with influenza-like illness.③The periodic vaccination with the vaccine against influenza A (H1N1) virus for those students from both the elementary and middle schools can effectively reduce the occurrence of clustered cases with influenza-like illness.