Article in Japanese

Comparison of the influenza vaccine effectiveness in Furano area from 2015/16 through 2018/19 seasons

Iori WAKABAYASHI¹⁾, Fujio KAKUYA¹⁾, Humie INYAKU²⁾, Hitosi OKUBO¹⁾, Hiroaki HUJIYASU¹⁾, Sarah Kyuragi LUTHE³⁾

This is a test-negative case-control study using medical record data of one primary care clinic and one secondary care hospital in Furano, Hokkaido, between four influenza seasons from 2015/16 through 2018/19. We included children (age 6 months to 18 years) with influenza-like illnesses and received influenza rapid diagnostic test (IRDT). We evaluated the vaccine effectiveness (VE) of inactivated influenza vaccine using the IRDT results. To determine the VE of inactivated influenza vaccine, we performed multivariable logistics regression analysis adjusting for age, sex, comorbidities, hospital, and onset month. VE was determined as VE=1-odds ratio. Among the 8,816 patients who visited with influenza-like illnesses, 3,904 were IRDT positive (2,340 with influenza A, and 1,564 with influenza B). Adjusted VE against both influenza types was 41-47%, influenza A was 37-54%, and influenza B was 31-39%. Adjusted VE by age showed a statistically significant VE of 40-59% in 6-23 months old group, 48-61% in 2-5 years old group, and 31-35% in 6-12 years old group, however, VE was low in 13-18 years old group. Comparisons between each season suggested that the VE of influenza A may be affected by the predominance of H3N2 compared to A (H1N1)pdm09. VE of influenza B were similar among 2015/16, 2016/17, and 2017/18 seasons. The comparison of regions showed differences in VE by age and type, suggesting that regional assessment may be important in examining VE.

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1) Department of Pediatrics, Furano Kyokai Hospital
2) Inyaku Pediatric Clinic
3) Department of Medicine, Indiana University

Key words	influenza vaccine, influenza, prevent infection, pediatrics, vaccination
Received	March 10, 2020
Accepted	October 7, 2020

32 (4)：333─344,2020