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- Title
Surveillance and Vaccine Effectiveness of an Influenza Epidemic Predominated by Vaccine-Mismatched Influenza B/Yamagata-Lineage Viruses in Taiwan, 2011−12 Season.
- Authors
Lo, Yi-Chun; Chuang, Jen-Hsiang; Kuo, Hung-Wei; Huang, Wan-Ting; Hsu, Yu-Fen; Liu, Ming-Tsan; Chen, Chang-Hsun; Huang, Hui-Hsun; Chang, Chi-Hsi; Chou, Jih-Haw; Chang, Feng-Yee; Lin, Tzou-Yien; Chiu, Wen-Ta
- Abstract
Introduction: The 2011−12 trivalent influenza vaccine contains a strain of influenza B/Victoria-lineage viruses. Despite free provision of influenza vaccine among target populations, an epidemic predominated by influenza B/Yamagata-lineage viruses occurred during the 2011−12 season in Taiwan. We characterized this vaccine-mismatched epidemic and estimated influenza vaccine effectiveness (VE). Methods: Influenza activity was monitored through sentinel viral surveillance, emergency department (ED) and outpatient influenza-like illness (ILI) syndromic surveillance, and case-based surveillance of influenza with complications and deaths. VE against laboratory-confirmed influenza was evaluated through a case-control study on ILI patients enrolled into sentinel viral surveillance. Logistic regression was used to estimate VE adjusted for confounding factors. Results: During July 2011−June 2012, influenza B accounted for 2,382 (72.5%) of 3,285 influenza-positive respiratory specimens. Of 329 influenza B viral isolates with antigen characterization, 287 (87.2%) were B/Yamagata-lineage viruses. Proportions of ED and outpatient visits being ILI-related increased from November 2011 to January 2012. Of 1,704 confirmed cases of influenza with complications, including 154 (9.0%) deaths, influenza B accounted for 1,034 (60.7%) of the confirmed cases and 103 (66.9%) of the deaths. Reporting rates of confirmed influenza with complications and deaths were 73.5 and 6.6 per 1,000,000, respectively, highest among those aged ≥65 years, 50−64 years, 3−6 years, and 0−2 years. Adjusted VE was −31% (95% CI: −80, 4) against all influenza, 54% (95% CI: 3, 78) against influenza A, and −66% (95% CI: −132, −18) against influenza B. Conclusions: This influenza epidemic in Taiwan was predominated by B/Yamagata-lineage viruses unprotected by the 2011−12 trivalent vaccine. The morbidity and mortality of this vaccine-mismatched epidemic warrants careful consideration of introducing a quadrivalent influenza vaccine that includes strains of both B lineages.
- Subjects
TAIWAN; INFLUENZA vaccines; EPIDEMICS; PHARMACODYNAMICS; PUBLIC health surveillance; ANTIVIRAL agents; VIRUS isolation
- Publication
PLoS ONE, 2013, Vol 8, Issue 3, p1
- ISSN
1932-6203
- Publication type
Article
- DOI
10.1371/journal.pone.0058222