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|Title:||Intraseason decline in influenza vaccine effectiveness during the 2016 southern hemisphere influenza season: a test-negative design study and phylogenetic assessment|
|Citation:||Vaccine, 2019; 37(19):2634-2641|
|Annette K.Regan, James E.Fielding, Monique B.Chilver, Kylie S.Carville, Cara A.Minney-Smith, Kristina A.Grant, Chloe Thomson, Trish Hahesy, Yi-Mo Deng, Nigel Stocks, Sheena G.Sullivan|
|Abstract:||BACKGROUND:We estimated the effectiveness of seasonal inactivated influenza vaccine and the potential influence of timing of immunization on vaccine effectiveness (VE) using data from the 2016 southern hemisphere influenza season. METHODS:Data were pooled from three routine syndromic sentinel surveillance systems in general practices in Australia. Each system routinely collected specimens for influenza testing from patients presenting with influenza-like illness. Next generation sequencing was used to characterize viruses. Using a test-negative design, VE was estimated based on the odds of vaccination among influenza-positive cases as compared to influenza-negative controls. Subgroup analyses were used to estimate VE by type, subtype and lineage, as well as age group and time between vaccination and symptom onset. RESULTS:A total of 1085 patients tested for influenza in 2016 were included in the analysis, of whom 447 (41%) tested positive for influenza. The majority of detections were influenza A/H3N2 (74%). One-third (31%) of patients received the 2016 southern hemisphere formulation influenza vaccine. Overall, VE was estimated at 40% (95% CI: 18-56%). VE estimates were highest for patients immunized within two months prior to symptom onset (VE: 60%; 95% CI: 26-78%) and lowest for patients immunized >4 months prior to symptom onset (VE: 19%; 95% CI: -73-62%). DISCUSSION:Overall, the 2016 influenza vaccine showed good protection against laboratory-confirmed infection among general practice patients. Results by duration of vaccination suggest a significant decline in effectiveness during the 2016 influenza season, indicating immunization close to influenza season offered optimal protection.|
|Keywords:||Case-control study; Influenza; Influenza vaccines; Test-negative design; Vaccine effectiveness|
|Rights:||Crown Copyright © 2019 Published by Elsevier Ltd. All rights reserved.|
|Appears in Collections:||Agriculture, Food and Wine publications|
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