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PLoS ONE. Post-Pandemic Seroprevalence of Pandemic Influenza A (H1N1) 2009 Infection (Swine Flu) among Children <18 Years in Germany
[Source: PLoS ONE, full text: (LINK). Abstract, edited.]
Post-Pandemic Seroprevalence of Pandemic Influenza A (H1N1) 2009 Infection (Swine Flu) among Children <18 Years in Germany
by R?diger von Kries, Susanne Weiss, Gerhard Falkenhorst, Stephan Wirth, Petra Kaiser, Hans-Iko Huppertz, Tobias Tenenbaum, Horst Schroten, Andrea Streng, Johannes Liese, Sonu Shai, Tim Niehues, Hermann Girschick, Ellen Kuscher, Axel Sauerbrey, Jochen Peters, Carl Heinz Wirsing von K?nig, Simon R?ckinger, Walter Hampl, Detlef Michel, Thomas Mertens
Background
We determined antibodies to the pandemic influenza A (H1N1) 2009 virus in children to assess: the incidence of (H1N1) 2009 infections in the 2009/2010 season in Germany, the proportion of subclinical infections and to compare titers in vaccinated and infected children.
Methodology/Principal Findings
Eight pediatric hospitals distributed over Germany prospectively provided sera from in- or outpatients aged 1 to 17 years from April 1<SUP>st</SUP> to July 31<SUP>st</SUP> 2010. Vaccination history, recall of infections and sociodemographic factors were ascertained. Antibody titers were measured with a sensitive and specific in-house hemagglutination inhibition test (HIT) and compared to age-matched sera collected during 6 months before the onset of the pandemic in Germany. We analyzed 1420 post-pandemic and 300 pre-pandemic sera. Among unvaccinated children aged 1?4 and 5?17 years the prevalence of HI titers (≥1∶10) was 27.1% (95% CI: 23.5?31.3) and 53.5% (95% CI: 50.9?56.2) compared to 1.7% and 5.5%, respectively, for pre-pandemic sera, accounting for a serologically determined incidence of influenza A (H1N1) 2009 during the season 2009/2010 of 25,4% (95% CI : 19.3?30.5) in children aged 1?4 years and 48.0% (95% CI: 42.6?52.0) in 5?17 year old children. Of children with HI titers ≥1∶10, 25.5% (95% CI: 22.5?28.8) reported no history of any infectious disease since June 2009. Among vaccinated children, 92% (95%-CI: 87.0?96.6) of the 5?17 year old but only 47.8% (95%-CI: 33.5?66.5) of the 1?4 year old children exhibited HI titers against influenza A virus (H1N1) 2009.
Conclusion
Serologically determined incidence of influenza A (H1N1) 2009 infections in children indicates high infection rates with older children (5?17 years) infected twice as often as younger children. In about a quarter of the children with HI titers after the season 2009/2010 subclinical infections must be assumed. Low HI titers in young children after vaccination with the AS03<SUB>B</SUB>-adjuvanted split virion vaccine need further scrutiny.
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by R?diger von Kries, Susanne Weiss, Gerhard Falkenhorst, Stephan Wirth, Petra Kaiser, Hans-Iko Huppertz, Tobias Tenenbaum, Horst Schroten, Andrea Streng, Johannes Liese, Sonu Shai, Tim Niehues, Hermann Girschick, Ellen Kuscher, Axel Sauerbrey, Jochen Peters, Carl Heinz Wirsing von K?nig, Simon R?ckinger, Walter Hampl, Detlef Michel, Thomas Mertens
Background
We determined antibodies to the pandemic influenza A (H1N1) 2009 virus in children to assess: the incidence of (H1N1) 2009 infections in the 2009/2010 season in Germany, the proportion of subclinical infections and to compare titers in vaccinated and infected children.
Methodology/Principal Findings
Eight pediatric hospitals distributed over Germany prospectively provided sera from in- or outpatients aged 1 to 17 years from April 1<SUP>st</SUP> to July 31<SUP>st</SUP> 2010. Vaccination history, recall of infections and sociodemographic factors were ascertained. Antibody titers were measured with a sensitive and specific in-house hemagglutination inhibition test (HIT) and compared to age-matched sera collected during 6 months before the onset of the pandemic in Germany. We analyzed 1420 post-pandemic and 300 pre-pandemic sera. Among unvaccinated children aged 1?4 and 5?17 years the prevalence of HI titers (≥1∶10) was 27.1% (95% CI: 23.5?31.3) and 53.5% (95% CI: 50.9?56.2) compared to 1.7% and 5.5%, respectively, for pre-pandemic sera, accounting for a serologically determined incidence of influenza A (H1N1) 2009 during the season 2009/2010 of 25,4% (95% CI : 19.3?30.5) in children aged 1?4 years and 48.0% (95% CI: 42.6?52.0) in 5?17 year old children. Of children with HI titers ≥1∶10, 25.5% (95% CI: 22.5?28.8) reported no history of any infectious disease since June 2009. Among vaccinated children, 92% (95%-CI: 87.0?96.6) of the 5?17 year old but only 47.8% (95%-CI: 33.5?66.5) of the 1?4 year old children exhibited HI titers against influenza A virus (H1N1) 2009.
Conclusion
Serologically determined incidence of influenza A (H1N1) 2009 infections in children indicates high infection rates with older children (5?17 years) infected twice as often as younger children. In about a quarter of the children with HI titers after the season 2009/2010 subclinical infections must be assumed. Low HI titers in young children after vaccination with the AS03<SUB>B</SUB>-adjuvanted split virion vaccine need further scrutiny.