Effectiveness of Influenza Vaccine in Preventing Medically-Attended Influenza Virus Infection in Primary Care, Israel, Influenza Seasons 2014/15 and 2015/16
Family and Community Medicine
IntroductionInfluenza vaccine is recommended for the entire population in Israel. We assessed influenza vaccine effectiveness (VE) for the 2014/15 and 2015/16 seasons in Israel, for the first time. Methods: Combined nose and throat swab specimens were collected from patients with influenza-like illness (ILI) presenting to sentinel primary care clinics and tested for influenza virus by RT-PCR. VE of the trivalent inactivated vaccine (TIV) was assessed using test-negative case-control design. Results: During the 2014/15 season 1,142 samples were collected; 327 (28.6%) were positive for influenza, 83.8% A(H3N2), 5.8% A(H1N1)pdm09, 9.2% B and 1.2% A un-subtyped. Adjusted VE against all influenza viruses for this influenza season was -4.8% (95% confidence interval (CI): -54.8 to 29.0) and against influenza A(H3N2), it was -15.8% (95% CI: -72.8 to 22.4). For the 2015/16 season, 1,919 samples were collected; 853 (44.4%) were positive for influenza, 43.5% A(H1N1)pdm09, 57% B, 0.7% A(H3N2) and 11 samples positive for both A(H1N1)pdm09 and B. Adjusted VE against all influenza viruses for this influenza season was 8.8% (95% CI: -25.1 to 33.5), against influenza A(H1N1)pdm09, it was 32.3% (95% CI: (-4.3 to 56.1) and against influenza B, it was -2.2% (95% CI: (-47.0 to 29.0). Conclusions: Using samples from patients with ILI visiting sentinel clinics in Israel, we demonstrated the feasibility of influenza VE estimation in Israel.
Yaron-Yakoby, H., Sefty, H., Pando, R., Dichtiar, R., Katz, M., Stein, Y., Mandelboim, M., Mendelson, E., Shohat, T., Glatman-Freedman, A., & The Israeli Influenza Surveillance Network (IISN). (2018). Effectiveness of Influenza Vaccine in Preventing Medically-Attended Influenza Virus Infection in Primary Care, Israel, Influenza Seasons 2014/15 and 2015/16. Euro Surveillance, 23 (7), 17-00026. https://doi.org/10.2807/1560-7917.ES.2018.23.7.17-00026