Y Drori1, R Pando2, H Sefty3, A Rosenberg3, E Mendelson4, L Keinan-Boker5, T Shohat6, M Mandelboim4, A Glatman-Freedman7. 1. Central Virology Laboratory, Chaim Sheba Medical Center, Israel Ministry of Health, Tel-Hashomer, Ramat Gan, Israel. 2. Central Virology Laboratory, Chaim Sheba Medical Center, Israel Ministry of Health, Tel-Hashomer, Ramat Gan, Israel; Israel Center for Disease Control, Ministry of Health, Tel Hashomer, Ramat Gan, Israel. 3. Israel Center for Disease Control, Ministry of Health, Tel Hashomer, Ramat Gan, Israel. 4. Central Virology Laboratory, Chaim Sheba Medical Center, Israel Ministry of Health, Tel-Hashomer, Ramat Gan, Israel; School of Public Health, Sackler School of Medicine, Tel Aviv University, Tel Aviv, Israel. 5. Israel Center for Disease Control, Ministry of Health, Tel Hashomer, Ramat Gan, Israel; School of Public Health, University of Haifa, Haifa, Israel. 6. Israel Center for Disease Control, Ministry of Health, Tel Hashomer, Ramat Gan, Israel; School of Public Health, Sackler School of Medicine, Tel Aviv University, Tel Aviv, Israel. 7. Israel Center for Disease Control, Ministry of Health, Tel Hashomer, Ramat Gan, Israel; School of Public Health, Sackler School of Medicine, Tel Aviv University, Tel Aviv, Israel. Electronic address: aharona.freedman@moh.health.gov.il.
Abstract
BACKGROUND: The 2017-2018 influenza season in Israel was characterized by the predominance of influenza B Yamagata, with a lesser circulation of influenza A(H1N1)pdm09 and influenza A(H3N2). We estimated vaccine effectiveness (VE) of the inactivated influenza vaccine which was selected for use that season. METHODS: End-of-season VE and 95% confidence intervals (CI) against laboratory-confirmed influenza-like illness (ILI) were estimated by means of the test-negative design. Age-specific VE analysis was carried out using a moving age interval. RESULTS: Specimen were obtained from 1,453 community ILI patients; 610 (42.0%) were influenza-positive, among which 69.7% were B, 17.2% A(H1N1)pdm09 and 13.4% A(H3N2). A 98.6% of molecularly characterized influenza B belonged to the Yamagata lineage. Of the sampled individuals, 1320 were suitable for VE analysis. Of those vaccinated, 90.6% received the inactivated trivalent influenza vaccine (TIV) containing a Victoria lineage influenza B-like virus. VE against influenza A differed by age, with the highest VE of 72.9% (95%CI 31.9-89.2%) observed in children 0.5-14 years old, while all ages VE was 46.6% (95%CI 10.4-68.2%). All ages VE against influenza B was 23.2% (95%CI -10.1-46.4%) with age-specific analysis showing non-significant VE estimates. Utilizing a moving age interval of 15 years, afforded a detailed age-specific insight into influenza VE against the influenza viruses circulating during the 2017-2018 season. CONCLUSIONS: The moderate-high 2017-2018 influenza A VE among children and adolescents, supports seasonal influenza vaccination at a young age. The low VE against influenza B in Israel, is most likely the result of influenza B/TIV-mismatch.
BACKGROUND: The 2017-2018 influenza season in Israel was characterized by the predominance of influenza B Yamagata, with a lesser circulation of influenza A(H1N1)pdm09 and influenza A(H3N2). We estimated vaccine effectiveness (VE) of the inactivated influenza vaccine which was selected for use that season. METHODS: End-of-season VE and 95% confidence intervals (CI) against laboratory-confirmed influenza-like illness (ILI) were estimated by means of the test-negative design. Age-specific VE analysis was carried out using a moving age interval. RESULTS: Specimen were obtained from 1,453 community ILI patients; 610 (42.0%) were influenza-positive, among which 69.7% were B, 17.2% A(H1N1)pdm09 and 13.4% A(H3N2). A 98.6% of molecularly characterized influenza B belonged to the Yamagata lineage. Of the sampled individuals, 1320 were suitable for VE analysis. Of those vaccinated, 90.6% received the inactivated trivalent influenza vaccine (TIV) containing a Victoria lineage influenza B-like virus. VE against influenza A differed by age, with the highest VE of 72.9% (95%CI 31.9-89.2%) observed in children 0.5-14 years old, while all ages VE was 46.6% (95%CI 10.4-68.2%). All ages VE against influenza B was 23.2% (95%CI -10.1-46.4%) with age-specific analysis showing non-significant VE estimates. Utilizing a moving age interval of 15 years, afforded a detailed age-specific insight into influenza VE against the influenza viruses circulating during the 2017-2018 season. CONCLUSIONS: The moderate-high 2017-2018 influenza A VE among children and adolescents, supports seasonal influenza vaccination at a young age. The low VE against influenza B in Israel, is most likely the result of influenza B/TIV-mismatch.