Un-In Wu1, Jann-Tay Wang1, Shan-Chwen Chang2, Yu-Chung Chuang1, Wei-Ru Lin3, Min-Chi Lu4, Po-Liang Lu3, Fu-Chang Hu5, Jen-Hsiang Chuang6, Yee-Chun Chen7. 1. Department of Internal Medicine, National Taiwan University Hospital, 7 Chung-Shan South Road, Zhongzheng District, Taipei 100, Taiwan. 2. Department of Internal Medicine, National Taiwan University Hospital, 7 Chung-Shan South Road, Zhongzheng District, Taipei 100, Taiwan; Center for Infection Control, National Taiwan University Hospital, Taipei, Taiwan. 3. Department of Internal Medicine, Kaohsiung Medical University Hospital, Kaohsiung, Taiwan. 4. Department of Internal Medicine, Chung-Shan Medical University Hospital, Taichung, Taiwan. 5. Graduate Institute of Clinical Medicine and School of Nursing, College of Medicine, National Taiwan University, Taipei, Taiwan. 6. Taiwan Centers for Disease Control, Taipei, Taiwan. 7. Department of Internal Medicine, National Taiwan University Hospital, 7 Chung-Shan South Road, Zhongzheng District, Taipei 100, Taiwan; Center for Infection Control, National Taiwan University Hospital, Taipei, Taiwan. Electronic address: yeechunchen@gmail.com.
Abstract
OBJECTIVES: A multicenter, hospital-wide, clinical and epidemiological study was conducted to assess the effectiveness of the mass influenza vaccination program during the 2009 H1N1 influenza pandemic, and the impact of the prioritization strategy among people at different levels of risk. METHODS AND RESULTS: Among the 34 359 medically attended patients who displayed an influenza-like illness and had a rapid influenza diagnostic test (RIDT) at one of the three participating hospitals, 21.0% tested positive for influenza A. The highest daily number of RIDT-positive cases in each hospital ranged from 33 to 56. A well-fitted multiple linear regression time-series model (R(2)=0.89) showed that the establishment of special community flu clinics averted an average of nine cases daily (p=0.005), and an increment of 10% in daily mean level of population immunity against pH1N1 through vaccination prevented five cases daily (p<0.001). Moreover, the regression model predicted five-fold or more RIDT-positive cases if the mass influenza vaccination program had not been implemented, and 39.1% more RIDT-positive cases if older adults had been prioritized for vaccination above school-aged children. CONCLUSIONS: Mass influenza vaccination was an effective control measure, and school-aged children should be assigned a higher priority for vaccination than older adults during an influenza pandemic.
OBJECTIVES: A multicenter, hospital-wide, clinical and epidemiological study was conducted to assess the effectiveness of the mass influenza vaccination program during the 2009 H1N1 influenza pandemic, and the impact of the prioritization strategy among people at different levels of risk. METHODS AND RESULTS: Among the 34 359 medically attended patients who displayed an influenza-like illness and had a rapid influenza diagnostic test (RIDT) at one of the three participating hospitals, 21.0% tested positive for influenza A. The highest daily number of RIDT-positive cases in each hospital ranged from 33 to 56. A well-fitted multiple linear regression time-series model (R(2)=0.89) showed that the establishment of special community flu clinics averted an average of nine cases daily (p=0.005), and an increment of 10% in daily mean level of population immunity against pH1N1 through vaccination prevented five cases daily (p<0.001). Moreover, the regression model predicted five-fold or more RIDT-positive cases if the mass influenza vaccination program had not been implemented, and 39.1% more RIDT-positive cases if older adults had been prioritized for vaccination above school-aged children. CONCLUSIONS: Mass influenza vaccination was an effective control measure, and school-aged children should be assigned a higher priority for vaccination than older adults during an influenza pandemic.