Influenza vaccination effectiveness in preventing influenza hospitalization in children, Hong Kong, winter 2019/20.


The winter influenza season 2019/20 in Hong Kong was predominated by influenza A(H1N1)pdm09. We analysed an on-going test-negative design study consisting of 1227 children admitted for febrile acute respiratory illness from 3 November 2019 (week 45) to 21 March 2020 (week 12). We estimated influenza vaccine effectiveness of 65% (95% CI: 46 - 78) against hospitalization due to influenza A and B combined, and 74% (95% CI: 54 - 85) against hospitalization due to influenza A(H1N1)pdm09.

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