Influenza-Associated Hospitalizations, Singapore, 2004–2008 and 2010–2012 - Volume 20, Number 10—October 2014 - Emerging Infectious Disease journal - CDC

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Influenza-Associated Hospitalizations, Singapore, 2004–2008 and 2010–2012 - Volume 20, Number 10—October 2014 - Emerging Infectious Disease journal - CDC

Volume 20, Number 10—October 2014

Research

Influenza-Associated Hospitalizations, Singapore, 2004–2008 and 2010–2012

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• Materials and Methods
• Results
• Discussion
• Suggested Citation

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• Figure 1
• Figure 2

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• Table 1
• Table 2
• Table 3

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Li Wei Ang , Cindy Lim, Vernon Jian Ming Lee, Stefan Ma, Wei Wei Tiong, Peng Lim Ooi, Raymond Tzer Pin Lin, Lyn James, and Jeffery Cutter

Author affiliations: Ministry of Health, Singapore (L.W. Ang, C. Lim, V.J.M. Lee, S. Ma, W.W. Tiong, P.L. Ooi, R.T.P. Lin, L. James, J. Cutter); Ministry of Defence, Singapore (V.J.M. Lee)

Suggested citation for this article

Abstract

Studies of influenza-associated hospitalizations in tropical settings are lacking. To increase understanding of the effect of influenza in Singapore, we estimated the age-specific influenza-associated hospitalizations for pneumonia and influenza during 2004–2008 and 2010–2012. The rate of hospitalization was 28.3/100,000 person-years during 2004–2008 and 29.6/100,000 person-years during 2010–2012. The age-specific influenza-associated hospitalization rates followed a J-shaped pattern: rates in persons >75 years of age and in children <6 months of age were >47 times and >26 times higher, respectively, than those for persons 25–44 years of age. Across all ages during these 2 study periods, ≈12% of the hospitalizations for pneumonia and influenza were attributable to influenza. The rates and proportions of hospitalizations attributable to influenza, particularly among the very young and the elderly, are considerable in Singapore and highlight the importance of vaccination in protecting populations at risk.

Seasonal influenza causes a substantial burden of illness worldwide. Infections can lead to severe illness that requires hospital care and can occasionally lead to death. Several studies have documented influenza-associated hospitalizations in countries with primarily temperate climates, such as the United States (1–5), and others have documented influenza-associated hospitalizations in subtropical regions, mostly in Hong Kong, China (6–8).

In the tropics, the spread of influenza is different from that in temperate regions because of the unique tropical climate and lack of clear climatic seasons (9,10). The baseline incidence of influenza infection is high, and >1 seasonal epidemic occurs each year (11). As documented in studies on influenza-associated deaths in Singapore (9,12), the effect of influenza epidemics in the tropics is comparable to its effect in other climatic regions. However, studies on influenza-associated hospitalizations in tropical settings are lacking. Such studies can provide an understanding of the pattern of hospitalizations and severe illness that is valuable in guiding public health policies.

Laboratory testing of specimens and virologic confirmation of influenza virus infections are not typically conducted for all patients and deaths; thus, the estimation of illness attributable to influenza cannot be based on reported episodes alone. Influenza can precipitate or exacerbate other respiratory and circulatory conditions, and there is a wide spectrum of clinical pathways and outcomes for influenza-associated conditions and complications. Pneumonia was ranked fifth in the list of top 10 conditions for hospitalization in Singapore in 2012 (13). There is a need to estimate the effect of influenza on health care utilization in terms of hospitalization for pneumonia and influenza.

Singapore has a robust data collection system, which facilitates the integration of databases from virologic surveillance for influenza and hospital systems. The aim of our study was to examine the influenza-associated hospitalization rates and proportions of pneumonia and influenza hospitalizations in Singapore. Age groups spanning <6 months to ≥75 years of age were examined to further identify the populations at greatest risk for influenza-associated hospitalizations.

Ms Ang is an assistant director in the Communicable Diseases Analytics unit of the Biostatistics and Research Branch, Epidemiology and Disease Control Division, at the Ministry of Health, Singapore. Her research interests include statistical applications, disease epidemiology, and public health surveillance.

Acknowledgment

We greatly appreciate and acknowledge the contribution of staff at the public acute-care hospitals, government primary care clinics, and private general practitioner clinics involved in the virologic surveillance for influenza. We thank the Research and Strategic Planning Division of the Health Promotion Board for sharing findings from the Health Behavior Surveillance of Singapore on the proportion of adults in Singapore who reported having been vaccinated against influenza.

References

1. Thompson WW, Shay DK, Weintraub E, Brammer L, Bridges CB, Cox NJ, Influenza-associated hospitalizations in the United States. JAMA.2004;292:1333–40. DOIPubMed
2. Mullooly JP, Bridges CB, Thompson WW, Chen J, Weintraub E, Jackson LA, ; Vaccine Safety Datalink Adult Working Group. Influenza- and RSV-associated hospitalizations among adults. Vaccine. 2007;25:846–55. DOIPubMed
3. Scuffham PA. Estimating influenza-related hospital admissions in older people from GP consultation data. Vaccine. 2004;22:2853–62.DOIPubMed
4. Azziz-Baumgartner E, Cabrera AM, Cheng PY, Garcia E, Kusznierz G, Calli R, Incidence of influenza-associated mortality and hospitalizations in Argentina during 2002–2009. Influenza Other Respir Viruses. 2013;7:710–7.
5. Newall AT, Wood JG, Macintyre CR. Influenza-related hospitalisation and death in Australians aged 50 years and older. Vaccine. 2008;26:2135–41.DOIPubMed
6. Chiu SS, Lau YL, Chan KH, Wong WH, Peiris JS. Influenza-related hospitalizations among children in Hong Kong. N Engl J Med. 2002;347:2097–103.DOIPubMed
7. Wong CM, Yang L, Chan KP, Leung GM, Chan KH, Guan Y, Influenza-associated hospitalization in a subtropical city. PLoS Med. 2006;3:e121.DOIPubMed
8. Yang L, Wang XL, Chan KP, Cao PH, Lau HY, Peiris JS, Hospitalisation associated with the 2009 H1N1 pandemic and seasonal influenza in Hong Kong, 2005 to 2010. Euro Surveill. 2012;17:20309 .PubMed
9. Lee VJ, Yap J, Ong JB, Chan KP, Lin RT, Chan SP, Influenza excess mortality from 1950–2000 in tropical Singapore. PLoS ONE. 2009;4:e8096.DOIPubMed
10. Yang L, Ma S, Chen PY, He JF, Chan KP, Chow A, Influenza associated mortality in the subtropics and tropics: results from three Asian cities. Vaccine.2011;29:8909–14. DOIPubMed
11. Viboud C, Alonso WJ, Simonsen L. Influenza in tropical regions. PLoS Med. 2006;3:e89. DOIPubMed
12. Chow A, Ma S, Ling AE, Chew SK. Influenza-associated deaths in tropical Singapore. Emerg Infect Dis. 2006;12:114–21. DOIPubMed
13. Ministry of Health. Singapore. Statistics: top 10 conditions of hospitalisation [cited 2014 Jul22].http://www.moh.gov.sg/content/moh_web/home/statistics/Health_Facts_Singapore/Top_10_Conditions_of_Hospitalisation.html
14. Department of Statistics, Ministry of Trade and Industry, Republic of Singapore. Population trends 2013 [cited 2014 Apr 12].http://www.singstat.gov.sg/publications/publications_and_papers/population_and_population_structure/population2013.pdf
15. Kostova D, Reed C, Finelli L, Cheng PY, Gargiullo PM, Shay DK, Influenza illness and hospitalizations averted by influenza vaccination in the United States, 2005–2011. PLoS ONE. 2013;8:e66312. DOIPubMed
16. Centers for Disease Control and Prevention. Estimated influenza illnesses and hospitalizations averted by influenza vaccination—United States, 2012–13 influenza season. MMWR Morb Mortal Wkly Rep. 2013;62:997–1000 .PubMed
17. Maciosek MV, Solberg LI, Coffield AB, Edwards NM, Goodman MJ. Influenza vaccination health impact and cost effectiveness among adults aged 50 to 64 and 65 and older. Am J Prev Med. 2006;31:72–9. DOIPubMed
18. Allsup S, Haycox A, Regan M, Gosney M. Is influenza vaccination cost effective for healthy people between ages 65 and 74 years? A randomised controlled trial. Vaccine. 2004;23:639–45 .PubMed
19. Nichol KL, Goodman M. Cost effectiveness of influenza vaccination for healthy persons between ages 65 and 74 years. Vaccine. 2002;20:S21–4.DOIPubMed
20. Nichol KL, Margolis KL, Wuorenma J, Von Sternberg T. The efficacy and cost effectiveness of vaccination against influenza among elderly persons living in the community. N Engl J Med. 1994;331:778–84. DOIPubMed
21. Hoshi SL, Kondo M, Honda Y, Okubo I. Cost-effectiveness analysis of influenza vaccination for people aged 65 and over in Japan. Vaccine.2007;25:6511–21. DOIPubMed
22. Lang PO, Mendes A, Socquet J, Assir N, Govind S, Aspinall R. Effectiveness of influenza vaccine in aging and older adults: comprehensive analysis of the evidence. Clin Interv Aging. 2012;7:55–64. DOIPubMed
23. Osterholm MT, Kelley NS, Sommer A, Belongia EA. Efficacy and effectiveness of influenza vaccines: a systematic review and meta-analysis. [Erratum in: Lancet Infect Dis. 2012;12:655]. Lancet Infect Dis. 2012;12:36–44. DOIPubMed
24. Deans GD, Stiver HG, McElhaney JE. Influenza vaccines provide diminished protection but are cost-saving in older adults. J Intern Med.2010;267:220–7. DOIPubMed
25. Jefferson T, Di Pietrantonj C, Al-Ansary LA, Ferroni E, Thorning S, Thomas RE. Vaccines for preventing influenza in the elderly. Cochrane Database Syst Rev. 2010;2:CD004876 .PubMed
26. Hurwitz ES, Haber M, Chang A, Shope T, Teo S, Ginsberg M, Effectiveness of influenza vaccination of day care children in reducing influenza-related morbidity among household contacts. JAMA. 2000;284:1677–82 and. DOIPubMed
27. Reichert TA, Sugaya N, Fedson DS, Glezen WP, Simonsen L, Tashiro M. The Japanese experience with vaccinating schoolchildren against influenza. N Engl J Med. 2001;344:889–96. DOIPubMed
28. Ghendon YZ, Kaira AN, Elshina GA. The effect of mass influenza immunization in children on the morbidity of the unvaccinated elderly. Epidemiol Infect. 2006;134:71–8. DOIPubMed
29. Cohen SA, Chui KK, Naumova EN. Influenza vaccination in young children reduces influenza-associated hospitalizations in older adults, 2002–2006.J Am Geriatr Soc. 2011;59:327–32. DOIPubMed
30. Centers for Disease Control and Prevention. Prevention and control of seasonal influenza with vaccines. Recommendations of the Advisory Committee on Immunization Practices—United States, 2013–2014. [Erratum in MMWR Recomm Rep. 2013;62:906]. MMWR Recomm Rep.2013;62(RR-07):1–43.
31. Chiu SS, Chan KH, Chen H, Young BW, Lim W, Wong WH, Virologically confirmed population-based burden of hospitalization caused by influenza A and B among children in Hong Kong. Clin Infect Dis. 2009;49:1016–21. DOIPubMed
32. Silvennoinen H, Peltola V, Vainionpää R, Ruuskanen O, Heikkinen T. Incidence of influenza-related hospitalizations in different age groups of children in Finland: a 16-year study. Pediatr Infect Dis J. 2011;30:e24–8. DOIPubMed
33. Poehling KA, Edwards KM, Weinberg GA, Szilagyi P, Staat MA, Iwane MK, The underrecognized burden of influenza in young children. N Engl J Med.2006;355:31–40. DOIPubMed
34. Dawood FS, Fiore A, Kamimoto L, Bramley A, Reingold A, Gershman K, Burden of seasonal influenza hospitalization in children, United States, 2003 to 2008. J Pediatr. 2010;157:808–14. DOIPubMed
35. Neuzil KM, Mellen BG, Wright PF, Mitchel EF Jr, Griffin MR. The effect of influenza on hospitalizations, outpatient visits, and courses of antibiotics in children. N Engl J Med. 2000;342:225–31. DOIPubMed
36. Fraaij PL, Heikkinen T. Seasonal influenza: the burden of disease in children. Vaccine. 2011;29:7524–8. DOIPubMed
37. Hong Kong Centre for Health Protection. Seasonal influenza vaccination survey for the 2012/13 season. Communicable Diseases Watch2013;10:74–5 [cited 2014 Jul 4]. http://www.chp.gov.hk/en/guideline1_year/29/134/112.html
38. Lu PJ, Santibanez TA, Williams WW, Zhang J, Ding H, Bryan L, Surveillance of influenza vaccination coverage—United States, 2007–08 through 2011–12 influenza seasons. MMWR Surveill Summ. 2013;62(Suppl 4):1–28 .PubMed
39. Zimmerman RK. Recent changes in influenza epidemiology and vaccination recommendations. J Fam Pract. 2005;54(Suppl):S1–8 .PubMed
40. Ministry of Health. Singapore. Statistics: healthcare institution statistics [cited 2014 Apr 12].http://www.moh.gov.sg/content/moh_web/home/statistics/healthcare_institutionstatistics.html

Figures

• Figure 1. Weekly number of hospitalizations for pneumonia and influenza and proportion of influenza-positive specimens as determined on the basis of virologic surveillance, Singapore, 2004–2008 and 2010–2012. A) Hospitalizations and diagnostic...
• Figure 2. Age-specific rates (per100,000 person-years) and proportions of influenza-associated hospitalizations for pneumonia and influenza, Singapore. A) 2004–2008 and B) 2010–2012. Black bold lines indicate influenza-associated hospitalization rate per 100,000 person-years;...

Tables

• Table 1. Virologic surveillance for influenza in Singapore during 2 study periods, 2004–2008 and 2010–2012
• Table 2. Age-specific hospitalization rates (per 100,000 person-years) for pneumonia and influenza in Singapore during 2 study periods, 2004–2008 and 2010–2012
• Table 3. Estimated influenza-associated hospitalizations for pneumonia and influenza in Singapore during 2 study periods, 2004–2008 and 2010–2012

Suggested citation for this article: Ang LW, Lim C, Lee VJM, Ma S, Tiong WW, Ooi PL, et al. Influenza-associated hospitalizations, Singapore, 2004–2008 and 2010–2012. Emerg Infect Dis. 2014 Oct [date cited]. http://dx.doi.org/10.3201/eid2010.131768

DOI: 10.3201/eid2010.131768