Comparison of influenza disease burden in older populations of Hong Kong and Brisbane: the impact of influenza and pneumococcal vaccination
Date
2019-02-14
Authors
Yang, Lin
Chan, King Pan
Wong, Chit Ming
Chiu, Susan Shui Seng
Magalhaes, Ricardo J. Soares
Thach, Thuan Quoc
Peiris, Joseph Syrial Malik
Clements, Archie
Hu, Wenbiao
Journal Title
Journal ISSN
Volume Title
Publisher
BioMed Central
Abstract
Background: Influenza and pneumococcal vaccine uptake in the older population aged 65 years or over of Hong
Kong dramatically increased since the 2003 SARS outbreak. This study is aimed to evaluate the impact of increased
coverage of influenza and pneumococcal vaccines by comparing the change of disease burden in the older population
of Hong Kong, with the burden in the older population of Brisbane with relatively high vaccine coverage in the past
fifteen years.
Methods: Time series segmented regression models were applied to weekly numbers of cause-specific mortality or
hospitalization of Hong Kong and Brisbane. Annual excess rates of mortality or hospitalization associated with influenza
in the older population were estimated for the pre-SARS (reference period), post-SARS and post-pandemic period,
respectively. The rate ratios (RRs) between these periods were also calculated to assess the relative change of
disease burden.
Results: Compared to the pre-SARS period, excess rates of mortality associated with influenza during the post-SARS
period in Hong Kong decreased for cardiorespiratory diseases (RR = 0.90, 95% CI 0.80, 1.01), stroke (RR = 0.74, 95%
CI 0.50, 1.09), and ischemic heart diseases (RR = 0.45, 95% CI 0.34, 0.58). The corresponding RRs in Brisbane were
0.79 (95% CI 0.54, 1.15), 0.33 (0.13, 0.80), and 1.09 (0.62, 1.90), respectively. Only the mortality of ischemic heart
diseases showed a greater reduction in Hong Kong than in Brisbane. During the post-pandemic period, excess
rates of all-cause mortality increased in Hong Kong, but to a lesser extent than in Brisbane (RR = 1.41 vs 2.39).
Conclusion: A relative decrease (or less of an increase) of influenza disease burden was observed in the older
population of Hong Kong after increased coverage of influenza and pneumococcal vaccines in this population, as
compared to those of Brisbane where vaccination rates remained stable. The lack of significant findings in some
disease categories highlights the challenges of evaluating the benefits of vaccination at the population level.
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Keywords
Influenza, Disease burden, Mortality, Morbidity, Elderly, Vaccine
Citation
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Source
BMC Infectious Diseases
Type
Journal article
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Open Access
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This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.
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