Hospitalization risk of the 2009 H1N1 pandemic cases in Hong Kong

Xi Ling Wang, Chit Ming Wong, Kwok Hung Chan, King Pan Chan, Pei Hua Cao, JS S.M. Peiris, Lin Yang

Research output: Journal article publicationJournal articleAcademic researchpeer-review

3 Citations (Scopus)


Background: Reliable assessment for the severity of the 2009 H1N1 pandemic influenza is critical for evaluation of vaccination strategies for future pandemics. This study aims to estimate the age-specific hospitalization risks of the 2009 pandemic cases during the first wave in Hong Kong, by combining the findings from the serology and disease burden studies.Methods: Excess hospitalization rates associated with the pandemic H1N1 were estimated from Poisson regression models fitted to weekly total numbers of non-accidental hospitalization from 2005 to 2010. Age-specific infection-hospitalization risks were calculated as excess hospitalization rates divided by the attack rates in the corresponding age group, which were estimated from serology studies previously conducted in Hong Kong.Results: Excess hospitalization rate associated with pandemic H1N1 was highest in the 0-4 age group (881.3 per 100,000 population), followed by the 5-14, 60+, 15-29, 50-59, 30-39 and 40-49 age groups. The hospitalization risk of the infected cases (i.e. infection-hospitalization risk) was found highest in the 60+ age group and lowest in the 15-29 age group, with the estimates of 17.5% and 0.7%, respectively.Conclusions: People aged 60 or over had a relatively high infection-hospitalization risk during the first wave of the 2009 H1N1 pandemic, despite of a low attack rate in this age group. The findings support the policy of listing older people as the priority group for pandemic vaccination.
Original languageEnglish
Article number32
JournalBMC Infectious Diseases
Issue number1
Publication statusPublished - 16 Jan 2014


  • Hospitalization
  • Influenza
  • Pandemic

ASJC Scopus subject areas

  • Infectious Diseases


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