Baum Ulrike, Ikonen Niina, Luomala Oskari, Poukka Eero, Leino Tuija, Nohynek Hanna
Department of Public Health, Finnish Institute for Health and Welfare, Helsinki, Finland.
Department of Public Health, Faculty of Medicine, University of Helsinki, Helsinki, Finland.
Influenza Other Respir Viruses. 2025 Jun;19(6):e70131. doi: 10.1111/irv.70131.
The Finnish influenza surveillance system combines traditional virological surveillance and analyses of electronic health records. This paper describes the influenza epidemiology in Finland (population: 5.5 million) during and after the COVID-19 pandemic based on national surveillance data from 2019 to 2024.
Influenza incidence was evaluated based on three register-based outcomes: laboratory-confirmed infections, primary health care visits, and hospitalizations. Virus-type distributions were analyzed from respiratory specimens. In register-based analyses, vaccination coverage and vaccine effectiveness were assessed for the two cohorts universally included in the Finnish vaccination program: children aged ≤ 6 years and adults aged ≥ 65 years.
The 2019/2020 influenza epidemic ended with the introduction of COVID-19 containment measures. In 2020/2021, influenza was largely absent. The 2021/2022 epidemic peaked exceptionally late. Influenza activity returned to prepandemic levels in 2022/2023. None of the 717 sentinel specimens tested positive for B/Yamagata. Although the percentage of vaccinated young children was constant (31% [100,387/323,614] to 37% [126,984/346,344]), the percentage of vaccinated elderly people increased from 48% (577,404/1,211,732) in 2019/2020 to 63% (787,771/1,255,644) in 2021/2022. The vaccine effectiveness against hospitalization due to laboratory-confirmed influenza in young children and elderly people was 68% (95% confidence interval: 38%; 83%) and 42% (34%; 50%) in 2022/2023, respectively, and slightly lower in 2023/2024.
The COVID-19 pandemic had two potentially lasting effects on influenza: elimination of the B/Yamagata lineage and improved vaccination coverage in the elderly population in Finland. To strengthen the Finnish influenza surveillance system, participation in sentinel surveillance must be improved.
芬兰流感监测系统结合了传统病毒学监测和电子健康记录分析。本文基于2019年至2024年的国家监测数据，描述了芬兰（人口550万）在新冠疫情期间及之后的流感流行病学情况。
基于三种基于登记的结果评估流感发病率：实验室确诊感染、初级医疗保健就诊和住院情况。从呼吸道标本中分析病毒类型分布。在基于登记的分析中，对芬兰疫苗接种计划普遍纳入的两个队列评估疫苗接种覆盖率和疫苗效力：6岁及以下儿童和65岁及以上成年人。
2019/2020年流感疫情随着新冠疫情防控措施的实施而结束。2020/2021年，流感基本未出现。2021/2022年疫情的高峰期异常晚。2022/2023年流感活动恢复到疫情前水平。717份哨点标本中没有一份检测出B/山形毒株呈阳性。尽管接种疫苗的幼儿比例保持稳定（从31%[100,387/323,614]到37%[126,984/346,344]），但接种疫苗的老年人比例从2019/2020年的48%（577,404/1,211,7,32）增加到2021/2022年的63%（787,771/1,255,644）。2022/2023年，针对实验室确诊流感导致住院的疫苗效力在幼儿和老年人中分别为68%（95%置信区间：38%；83%）和42%（34%；50%），在2023/2024年略低。
新冠疫情对流感有两个潜在的持久影响：消除了B/山形谱系，提高了芬兰老年人群的疫苗接种覆盖率。为加强芬兰流感监测系统，必须提高哨点监测的参与度。
