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. 2021 Sep;93(9):5626-5629.
doi: 10.1002/jmv.27048. Epub 2021 May 12.

Influenza season 2020-2021 did not begin in Finland despite the looser social restrictions during the second wave of COVID-19: A nationwide register study

Ilari Kuitunen  1   2
Affiliations

Influenza season 2020-2021 did not begin in Finland despite the looser social restrictions during the second wave of COVID-19: A nationwide register study

Ilari Kuitunen. J Med Virol. 2021 Sep.

Abstract

The nationwide lockdowns ended influenza seasons rapidly in Northern Hemisphere in Spring 2020. The strategy during the second wave was to minimize the restrictions set for children. Children spread influenza and therefore simultaneous influenza and COVID-19 surges were feared. The aim of this report is to analyze the epidemiology of influenza season 2020-2021 in Finland. Data for this retrospective register-based study were gathered from the National Infectious Disease Register, all laboratory-confirmed influenza cases from August 2017 to March 2021 were included. The positive influenza findings were stratified by age, and incidences per 100 000 persons were calculated. Only 41 influenza A and B cases have been reported in this season from August 2020 to March 2021, which adds up to an incidence of 0.9 per 100 000 person-years. In the three preceding years, the numbers and corresponding incidences from August to March were 12 461 (282 per 100 000 person-years) in 2019-2020, 15 276 (346 per 100 000 person-years) in 2018-2019, and 33 659 (761 per 100 000 person-years) in 2017-2018. Nonpharmaceutical interventions combined with the lockdown measures interrupted the influenza season in Finland in March 2020. Despite looser restrictions, alongside traveling restrictions and facial masks, failing to prevent the spread of the severe acute respiratory syndrome coronavirus 2 virus, these restrictions have proved to be effective against seasonal influenza.

Keywords: epidemiology; influenza; nonpharmaceutical interventions.

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Conflict of interest statement

The authors declare that there are no conflict of interests.

Figures

Figure 1
Figure 1
Monthly incidences per 100 000 persons of positive influenza A and B in Finland from August 2017 to March 2021. The data is stratified by age
See this image and copyright information in PMC

References

    1. Fricke LM, Glöckner S, Dreier M, Lange B. Impact of non‐pharmaceutical interventions targeted at COVID‐19 pandemic on influenza burden—a systematic review. J Infect. 2021;82(1):1‐35. 10.1016/j.jinf.2020.11.039 - DOI - PMC - PubMed
    1. Kuitunen I, Artama M, Mäkelä L, Backman K, Heiskanen‐Kosma T, Renko M. Effect of social distancing due to the COVID‐19 pandemic on the incidence of viral respiratory tract infections in children in finland during early 2020. Pediatr Infect Dis J. 2020;39(12):e423‐e427. 10.1097/INF.0000000000002845 - DOI - PubMed
    1. Trenholme A, Webb R, Lawrence S, et al. COVID‐19 and infant hospitalizations for seasonal respiratory virus infections, New Zealand, 2020. Emerg Infect Dis. 2021;27(2):641‐643. 10.3201/eid2702.204041 - DOI - PMC - PubMed
    1. Jefferson T, Del Mar CB, Dooley L, et al. Physical interventions to interrupt or reduce the spread of respiratory viruses. Cochrane Database Syst Rev. 2020;11:CD006207. 10.1002/14651858.CD006207.pub5 - DOI - PMC - PubMed
    1. Cauchemez S, Valleron AJ, Boëlle PY, Flahault A, Ferguson NM. Estimating the impact of school closure on influenza transmission from Sentinel data. Nature. 2008;452(7188):750‐754. 10.1038/nature06732 - DOI - PubMed

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