Was the Reduction in Seasonal Influenza Transmission during 2020 Attributable to Non-Pharmaceutical Interventions to Contain Coronavirus Disease 2019 (COVID-19) in Japan?

Viruses. 2022 Jun 28;14(7):1417. doi: 10.3390/v14071417.

Abstract

We quantified the effects of adherence to various non-pharmaceutical interventions (NPIs) on the seasonal influenza epidemic dynamics in Japan during 2020. The total monthly number of seasonal influenza cases per sentinel site (seasonal influenza activity) reported to the National Epidemiological Surveillance of Infectious Diseases and alternative NPI indicators (retail sales of hand hygiene products and number of airline passenger arrivals) from 2014−2020 were collected. The average number of monthly seasonal influenza cases in 2020 had decreased by approximately 66.0% (p < 0.001) compared to those in the preceding six years. An increase in retail sales of hand hygiene products of ¥1 billion over a 3-month period led to a 15.5% (95% confidence interval [CI]: 10.9−20.0%; p < 0.001) reduction in seasonal influenza activity. An increase in the average of one million domestic and international airline passenger arrivals had a significant association with seasonal influenza activity by 11.6% at lag 0−2 months (95% CI: 6.70−16.5%; p < 0.001) and 30.9% at lag 0−2 months (95% CI: 20.9−40.9%; p < 0.001). NPI adherence was associated with decreased seasonal influenza activity during the COVID-19 pandemic in Japan, which has crucial implications for planning public health interventions to minimize the health consequences of adverse seasonal influenza epidemics.

Keywords: COVID-19; NPIs; SARS-CoV-2; epidemics; seasonal influenza.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • COVID-19* / epidemiology
  • COVID-19* / prevention & control
  • Humans
  • Influenza, Human* / epidemiology
  • Influenza, Human* / prevention & control
  • Japan / epidemiology
  • Pandemics / prevention & control
  • Seasons

Grants and funding

K.W. received funding from the Community Medical Research Grant by the Niigata City Medical Association (GC03220213) and the BIKEN Taniguchi Scholarship from the Research Institute for Microbial Diseases, Osaka University, Osaka, Japan (RIMD) (grant number not available). R.S. received funding from the Japan Initiative for Global Research Network on Infectious Diseases (J-GRID) by the Japan Agency for Medical Research and Development (AMED) (15fm0108009h0001–21wm0125005h0002); Grants-in-Aid for Scientific Research (KAKENHI) by the Japan Society for the Promotion of Science (JSPS) (21K10414); the Health and Labor Sciences Research Grants, Ministry of Health, Labor and Welfare, Japan (H30-Shinkougyousei-Shitei-002 and H30-Shinkougyousei-Shitei-004); and the Niigata Prefecture Coronavirus Infectious Disease Control Research and Human Resources Development Support Fund (grant number not available). The funder of the study had no role in the study design, data collection, data analysis, data interpretation, or writing of the manuscript.