Evaluation on protective effect of influenza vaccine among people aged 70 years and older in Jiaxing City / 预防医学

ABSTRACT

Objective@#To evaluate the protective effect of influenza vaccine among people aged 70 years and older in Jiaxing City, Zhejiang Province, so as to provide a basis for formulating immunization strategies.@*Methods@#The influenza-like illness (ILI) cases aged 70 years and older treated in influenza surveillance sentinel hospital in Jiaxing City from November 2022 to May 2023 were selected. The medical information and influenza vaccination information were collected by a questionnaire survey, and influenza virus was detected using the quantitative fluorescent real-time PCR assay. The test-negative design case-control study was used to analyze the influencing factors of influenza virus positive and evaluate vaccine effect (VE).@*Results@#Totally 1 084 ILI cases were enrolled, including 535 males (49.35%) and 549 females (50.64%). There were 732 cases (67.53%) aged 70 to 79 years, and 352 cases (32.47%) aged 80 years and older. There were 689 cases with underlying diseases, accounting for 63.56%. A total of 224 influenza virus positive samples were detected, with a positive rate of 20.66%. Multivariable logistic regression analysis showed that a lower possibility of influenza virus positive was seen in ILI cases aged 80 years and older, with underlying diseases and with influenza vaccination in the current season (all P<0.05). A total of 345 cases were vaccinated against influenza in the current season, with a vaccination rate of 31.83%. The VE of influenza vaccine was 37.40% (95%CI: 12.40%-55.40%), of which the VE to A (H1N1) was 36.00% (95%CI: 7.50%-55.70%) and to A (H3N2) was 40.90% (95%CI: -26.00%-72.30%). The VE for ILI cases aged 70 to 79 years was 41.00% (95%CI: 13.90%-59.60%), and for ILI cases aged 80 years and older was 20.60% (95%CI: -64.60%-61.70%).@*Conclusions@#Influenza vaccine has a certain protective effect on cases aged 70 years and older. Free influenza vaccination for the elderly should be continuously promoted and the vaccination coverage should be increased.