In the 2016-2017 season, the A(H3N2) influenza epidemic presented an unusual early peak pattern compared with past seasons in South Korea. The interim vaccine effectiveness (VE) of influenza vaccination in preventing laboratory-confirmed influenza was estimated using test-negative design through the tertiary hospital-based influenza surveillance system in South Korea. From 1 September, 2016 to 7 January, 2017, adjusted VE of influenza vaccination in preventing laboratory-confirmed A(H3N2) was -52.1% (95% confidence interval [CI], -147.2 to 6.4); -70.0% (95% CI, -212.0 to 7.4) in 19-64 years and 4.3% (95% CI, -137.8 to 61.5) in the elderly. Circulating A(H3N2) viruses belonged to the three phylogenetic subclades of 3C.2a, differently to A/Hong Kong/4801/2014, the current vaccine strain. Amino acid substitutions in hemagglutinin of circulating viruses seem to contribute to low VE. In conclusion, interim VE analysis presented that the protection of laboratory-confirmed influenza by seasonal influenza vaccination did not show the statistical significance in South Korea in the 2016-2017 influenza season.
Bibliographical noteFunding Information:
This work was supported by a grant of the TEPIK (Transgovernmental Enterprise for Pandemic Influenza in Korea) which is a part of the Korea Healthcare Technology R&D Project by Ministry of Health & Welfare, Republic of Korea (Grant no.: A103001) and by the National Research Foundation of Korea (NRF) Grant funded by the Korean Government (MSIP) (NRF- 2016R1A5A1010148). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.
© 2017 Noh et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
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