| [Background]China is the first country to launch a vaccination campaign of 2009 pandemic A(H1N1) influenza vaccine, before the license of this vaccine, only serological evidenceunder laboratory condition were available, effectiveness assessments on disease outcome in practical environment using epidemiological methods were in an urgent need.China is keeping a well-organized sentinelsurveillancesystem of influenza based on clinics in hospitals and network laboratories, which doing etiological testing on oral/nasal swabs from influenza-like illness patients, possessing the capacity of epidemiological assessment on influenza vaccine effectiveness.Jiang Su province was launching a vaccination campaign of 2009 pandemic A(H1N1) influenza vaccine on target people since November 2009. Influenza surveillance in this province showed that, in week 28th 2009, epidemic strength of 2009 pandemic A(H1N1) influenza reached peak, for positive rate of sentinel surveillance consisting of 29 sentinel hospitals was 68.46%, among which 98.35% was positive on this pandemic influenza virus. Based on this sentinel surveillance, quick assessment of 2009 pandemic A(H1N1) influenza vaccine was practical.[Objective]Quick assessment of 2009 pandemic A(H1N1) influenza vaccine on reducing influenza-like illness hospital-consulting laboratory confirmed cases, and measurement of potential bias in this project, offer evidence for future research.[Method]This project used nested case-control study, defining study subject as during January to March 2010,patients who consulted sentinelhospital clinics for influenza like illness and were taken oral/nasal swabs for network laboratory test, adding that this patient belonging to appropriate groups for 2009 pandemic A(H1N1) influenza vaccination. Doctors or nurses used <ILI patients interview questionnaire> to do a retrospective investigation on study subjects, gathering illness onset time,2009 pandemic A(H1N1) influenza vaccination history, age, gender, underlying condition, consulting times in the past year, etc. Subjects having pandemic influenza positive test result were cases, two types of controls were positive for other influenza and negative for all types influenza. Exposures were defined differently on interval between vaccination date and illness onset date. After stratification and multivariate analysis to control potential influencing factors, independent effect of 2009 pandemic A(H1N1) influenza vaccine was obtained. Using formula VE= (1-RR(OR))*100%,2009 pandemic A(H1N1) influenza vaccine effectiveness was achieved.[Outcome]During 5th January to 31th March,29 sentinel hospitals completed 2764 valid questionnaire. Disease onset time of study subjects were mainly on 2010 week 2nd to week 8th, age range was 6 months to 95 years old,with median age was 23 years old, occupation was mainly student. Positive rate for pandemic influenza was 6.9%, vaccination rate was 10.8%.OR of pandemic influenza vaccine using univariate analysis was 0.95(0.59-1.54).After stratification and multivariate analysis, time change and area difference of epidemic intensity, consulting times in the past year, interval of disease onset and consulting were potential influencing factors. Restricting on subject with onset time belonging to pandemic virus circulating period, exposure being defined as interval of vaccination and disease onset was larger than 14 days, controls being consisted with positive for other types influenza, the most accurate VE was obtained, which was 51%(CI:7%-75%), and for 3-18 years old, which were the main vaccination subjects in this project, VE was 57%(CI:5%-81%)This VE had large CI demonstrate a small sample size. For VE(51%) calculated from RR was lower than other research result from China and other country, several bias could explain this underestimation.[Conclusion]2009 pandemic A(H1N1) influenza vaccine effectiveness obtained in this project was 51%(CI: 7%-75%), for 3-18 years old, VE was 57%(CI:5%-81%), which may suffered small sample size and several bias. |
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