Yamamoto Shohei, Mizoue Tetsuya, Ujiie Mugen, Horii Kumi, Takeuchi Junko S, Konishi Maki, Sugiura Wataru, Ohmagari Norio
Department of Epidemiology and Prevention, Center for Clinical Sciences, Japan Institute for Health Security, Tokyo, Japan.
Vaccination Support Center, Disease Control and Prevention Center, Japan Institute for Health Security, Tokyo.
J Infect Dis. 2025 Apr 10. doi: 10.1093/infdis/jiaf183.
After the prolonged COVID-19 pandemic, during which the seasonal influenza epidemic was suppressed, Japan experienced a record-breaking influenza A/H1N1 outbreak in the 2024/2025 season. This situation also raises a concern about the immunogenicity of the annual inactivated influenza vaccine. This study evaluated post-vaccination hemagglutination inhibition (HI) antibody titers and their association with influenza infection risk among healthcare workers.
A serosurvey was conducted among staff at a national medical and research center in Tokyo in December 2024, one month after staff received the inactivated influenza vaccine. HI antibody titers against vaccine strains were measured, and participants were followed for influenza infection until January 2025. Seroprotection was defined as an HI titer ≥40. A Cox proportional hazards model assessed the association between HI titers and infection risk among vaccinated participants.
Among 1,507 vaccinated participants, only 12.7% had seroprotective HI titers against A/H1N1. Around 90% had no influenza history for at least four seasons and had received repeated vaccinations over two seasons. Participants with HI titers <40 had a 4-fold higher infection risk than those with titers ≥40. A dose-response association was observed, even within the range below the titer of 40. Relative to titers <10, titers of 10 and 20 conferred 47.3% and 57.9% protection, respectively.
After a prolonged period without a major influenza epidemic, HI titers against A/H1N1 were extremely low in vaccinated healthcare workers. Nonetheless, higher post-vaccination HI titers, even at relatively low levels, were associated with protection, supporting the benefit of vaccines.
在长期的新冠疫情期间，季节性流感疫情受到抑制，日本在2024/2025季节经历了创纪录的甲型H1N1流感爆发。这种情况也引发了对年度灭活流感疫苗免疫原性的担忧。本研究评估了医护人员接种疫苗后的血凝抑制（HI）抗体滴度及其与流感感染风险的关联。
2024年12月，在东京一家国家医学和研究中心的工作人员接种灭活流感疫苗一个月后，对其进行了血清学调查。测量了针对疫苗株的HI抗体滴度，并对参与者进行流感感染跟踪，直至2025年1月。血清保护定义为HI滴度≥40。采用Cox比例风险模型评估接种疫苗参与者中HI滴度与感染风险之间的关联。
在1507名接种疫苗的参与者中，只有12.7%的人对甲型H1N1具有血清保护性HI滴度。约90%的人至少四个季节没有流感病史，并且在两个季节内接受了多次疫苗接种。HI滴度<40的参与者感染风险比滴度≥40的参与者高4倍。即使在40滴度以下的范围内，也观察到了剂量反应关联。相对于滴度<10，滴度为10和20时分别提供了47.3%和57.9%的保护。
在长时间没有重大流感疫情之后，接种疫苗的医护人员中针对甲型H1N1的HI滴度极低。尽管如此，即使是相对较低水平的较高接种后HI滴度也与保护相关，支持了疫苗的益处。
