Seroprevalence and severity of 2009 pandemic influenza a H1N1 in Taiwan

Chih Jung Chen, Ping Ing Lee, Shih Cheng Chang, Yhu Chering Huang, Cheng Hsun Chiu, Yu Chia Hsieh, Shang Chwen Chang, Feng Yee Chang, Jen Jyh Lee, Shey Chiang Su, Gwan Han Shen, Yin Ching Chuang, Yao Shen Chen, Jien Wei Liu, Tzou Yien Lin

Research output: Contribution to journalArticle

15 Citations (Scopus)

Abstract

Background: This study is to determine the seroprevalence of the pandemic influenza A H1N1 virus (pH1N1) in Taiwan before and after the 2009 pandemic, and to estimate the relative severity of pH1N1 infections among different age groups. Methodology/Principal Findings: A total of 1544 and 1558 random serum samples were collected from the general population in Taiwan in 2007 and 2010, respectively. Seropositivity was defined by a hemagglutination inhibition titer to pH1N1 (A/Taiwan/126/09) ≥1:40. The seropositivity rate of pH1N1 among the unvaccinated subjects and national surveillance data were used to compare the proportion of infections that led to severe diseases and fatalities among different age groups. The overall seroprevalence of pH1N1 was 0.91% (95% confidence interval [CI] 0.43-1.38) in 2007 and significantly increased to 29.9% (95% CI 27.6-32.2) in 2010 (p<0.0001), with the peak attack rate (55.4%) in 10-17 year-old adolescents, the lowest in elderly ≥65 years (14.1%). The overall attack rates were 20.6% (188/912) in unvaccinated subjects. Among the unvaccinated but infected populations, the estimated attack rates of severe cases per 100,000 infections were significantly higher in children aged 0-5 years (54.9 cases, odds ratio [OR] 4.23, 95% CI 3.04-5.90) and elderly ≥ 65years (22.4 cases, OR 2.76, 95% CI 1.99-3.83) compared to adolescents aged 10-17 years (13.0 cases). The overall case-fatality rate was 0.98 per 100,000 infections without a significant difference in different age groups. Conclusions/Significance: Pre-existing immunity against pH1N1 was rarely identified in Taiwanese at any age in 2007. Young children and elderly - the two most lower seroprotection groups showed the greatest vulnerability to clinical severity after the pH1N1 infections. These results imply that both age groups should have higher priority for immunization in the coming flu season.

Original languageEnglish
Article numbere24440
JournalPLoS One
Volume6
Issue number9
DOIs
Publication statusPublished - Sep 1 2011
Externally publishedYes

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Immunization
Seroepidemiologic Studies
Pandemics
pandemic
Taiwan
Viruses
influenza
seroprevalence
Human Influenza
confidence interval
Age Groups
Confidence Intervals
Infection
infection
odds ratio
Odds Ratio
H1N1 Subtype Influenza A Virus
Influenza A virus
Hemagglutination
hemagglutination

ASJC Scopus subject areas

  • Agricultural and Biological Sciences(all)
  • Biochemistry, Genetics and Molecular Biology(all)
  • Medicine(all)

Cite this

Chen, C. J., Lee, P. I., Chang, S. C., Huang, Y. C., Chiu, C. H., Hsieh, Y. C., ... Lin, T. Y. (2011). Seroprevalence and severity of 2009 pandemic influenza a H1N1 in Taiwan. PLoS One, 6(9), [e24440]. https://doi.org/10.1371/journal.pone.0024440

Seroprevalence and severity of 2009 pandemic influenza a H1N1 in Taiwan. / Chen, Chih Jung; Lee, Ping Ing; Chang, Shih Cheng; Huang, Yhu Chering; Chiu, Cheng Hsun; Hsieh, Yu Chia; Chang, Shang Chwen; Chang, Feng Yee; Lee, Jen Jyh; Su, Shey Chiang; Shen, Gwan Han; Chuang, Yin Ching; Chen, Yao Shen; Liu, Jien Wei; Lin, Tzou Yien.

In: PLoS One, Vol. 6, No. 9, e24440, 01.09.2011.

Research output: Contribution to journalArticle

Chen, CJ, Lee, PI, Chang, SC, Huang, YC, Chiu, CH, Hsieh, YC, Chang, SC, Chang, FY, Lee, JJ, Su, SC, Shen, GH, Chuang, YC, Chen, YS, Liu, JW & Lin, TY 2011, 'Seroprevalence and severity of 2009 pandemic influenza a H1N1 in Taiwan', PLoS One, vol. 6, no. 9, e24440. https://doi.org/10.1371/journal.pone.0024440
Chen CJ, Lee PI, Chang SC, Huang YC, Chiu CH, Hsieh YC et al. Seroprevalence and severity of 2009 pandemic influenza a H1N1 in Taiwan. PLoS One. 2011 Sep 1;6(9). e24440. https://doi.org/10.1371/journal.pone.0024440
Chen, Chih Jung ; Lee, Ping Ing ; Chang, Shih Cheng ; Huang, Yhu Chering ; Chiu, Cheng Hsun ; Hsieh, Yu Chia ; Chang, Shang Chwen ; Chang, Feng Yee ; Lee, Jen Jyh ; Su, Shey Chiang ; Shen, Gwan Han ; Chuang, Yin Ching ; Chen, Yao Shen ; Liu, Jien Wei ; Lin, Tzou Yien. / Seroprevalence and severity of 2009 pandemic influenza a H1N1 in Taiwan. In: PLoS One. 2011 ; Vol. 6, No. 9.
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abstract = "Background: This study is to determine the seroprevalence of the pandemic influenza A H1N1 virus (pH1N1) in Taiwan before and after the 2009 pandemic, and to estimate the relative severity of pH1N1 infections among different age groups. Methodology/Principal Findings: A total of 1544 and 1558 random serum samples were collected from the general population in Taiwan in 2007 and 2010, respectively. Seropositivity was defined by a hemagglutination inhibition titer to pH1N1 (A/Taiwan/126/09) ≥1:40. The seropositivity rate of pH1N1 among the unvaccinated subjects and national surveillance data were used to compare the proportion of infections that led to severe diseases and fatalities among different age groups. The overall seroprevalence of pH1N1 was 0.91{\%} (95{\%} confidence interval [CI] 0.43-1.38) in 2007 and significantly increased to 29.9{\%} (95{\%} CI 27.6-32.2) in 2010 (p<0.0001), with the peak attack rate (55.4{\%}) in 10-17 year-old adolescents, the lowest in elderly ≥65 years (14.1{\%}). The overall attack rates were 20.6{\%} (188/912) in unvaccinated subjects. Among the unvaccinated but infected populations, the estimated attack rates of severe cases per 100,000 infections were significantly higher in children aged 0-5 years (54.9 cases, odds ratio [OR] 4.23, 95{\%} CI 3.04-5.90) and elderly ≥ 65years (22.4 cases, OR 2.76, 95{\%} CI 1.99-3.83) compared to adolescents aged 10-17 years (13.0 cases). The overall case-fatality rate was 0.98 per 100,000 infections without a significant difference in different age groups. Conclusions/Significance: Pre-existing immunity against pH1N1 was rarely identified in Taiwanese at any age in 2007. Young children and elderly - the two most lower seroprotection groups showed the greatest vulnerability to clinical severity after the pH1N1 infections. These results imply that both age groups should have higher priority for immunization in the coming flu season.",
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AU - Chen, Chih Jung

AU - Lee, Ping Ing

AU - Chang, Shih Cheng

AU - Huang, Yhu Chering

AU - Chiu, Cheng Hsun

AU - Hsieh, Yu Chia

AU - Chang, Shang Chwen

AU - Chang, Feng Yee

AU - Lee, Jen Jyh

AU - Su, Shey Chiang

AU - Shen, Gwan Han

AU - Chuang, Yin Ching

AU - Chen, Yao Shen

AU - Liu, Jien Wei

AU - Lin, Tzou Yien

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N2 - Background: This study is to determine the seroprevalence of the pandemic influenza A H1N1 virus (pH1N1) in Taiwan before and after the 2009 pandemic, and to estimate the relative severity of pH1N1 infections among different age groups. Methodology/Principal Findings: A total of 1544 and 1558 random serum samples were collected from the general population in Taiwan in 2007 and 2010, respectively. Seropositivity was defined by a hemagglutination inhibition titer to pH1N1 (A/Taiwan/126/09) ≥1:40. The seropositivity rate of pH1N1 among the unvaccinated subjects and national surveillance data were used to compare the proportion of infections that led to severe diseases and fatalities among different age groups. The overall seroprevalence of pH1N1 was 0.91% (95% confidence interval [CI] 0.43-1.38) in 2007 and significantly increased to 29.9% (95% CI 27.6-32.2) in 2010 (p<0.0001), with the peak attack rate (55.4%) in 10-17 year-old adolescents, the lowest in elderly ≥65 years (14.1%). The overall attack rates were 20.6% (188/912) in unvaccinated subjects. Among the unvaccinated but infected populations, the estimated attack rates of severe cases per 100,000 infections were significantly higher in children aged 0-5 years (54.9 cases, odds ratio [OR] 4.23, 95% CI 3.04-5.90) and elderly ≥ 65years (22.4 cases, OR 2.76, 95% CI 1.99-3.83) compared to adolescents aged 10-17 years (13.0 cases). The overall case-fatality rate was 0.98 per 100,000 infections without a significant difference in different age groups. Conclusions/Significance: Pre-existing immunity against pH1N1 was rarely identified in Taiwanese at any age in 2007. Young children and elderly - the two most lower seroprotection groups showed the greatest vulnerability to clinical severity after the pH1N1 infections. These results imply that both age groups should have higher priority for immunization in the coming flu season.

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