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Factors influencing infection by pandemic influenza A(H1N1)pdm09 over three epidemic waves in Singapore
Mark I. C. Chen1,2,
Alex R. Cook1,2,3,4,
Wei Yen Lim1,
Raymond Lin5,
Lin Cui5,
Ian G. Barr6,
Anne Kelso6,
Vincent T. Chow7,
Yee Sin Leo1,2,
Jung Pu Hsu7,
Rob Shaw6,
Serene Chew2,
Joe Kwan Yap2,
Meng Chee Phoon7,
Hiromi W. L. Koh1,
Huili Zheng1,
Linda Tan1,
Vernon J. Lee1,2,*
Article first published online: 5 JUL 2013
DOI: 10.1111/irv.12129
Introduction
Previous influenza pandemics had second and on occasion third waves in many countries that were at times more severe than the initial pandemic waves.
Objective
This study aims to determine the seroepidemiology of successive waves of H1N1pdm09 infections in Singapore and the overall risks of infection.
Methods
We performed a cohort study amongst 838 adults, with blood samples provided upon recruitment and at 5 points from 2009 to 2011 and tested by haemagglutination inhibition (HI) with A/California/7/2009 (H1N1pdm09). Surveys on key demographic and clinical information were conducted at regular intervals, and associations between seroconversion and these variables were investigated.
Results
After the initial wave from June to September 2009, second and third waves occurred from November 2009 to February 2010 and April to June 2010, respectively. Seroconversion was 13?5% during the first wave and decreased to 6?2% and 6?8% in subsequent waves. Across the three waves, the elderly and those with higher starting HI titres were at lower risk of seroconversion, while those with larger households were at greater risk. Those with higher starting HI titres were also less likely to have an acute respiratory infection.
Conclusions
The second and third waves in Singapore had lower serological attack rates than the first wave. The elderly and those with higher HI titres had lower risk, while those in larger households had higher risk of seroconversion.
http://onlinelibrary.wiley.com/doi/10.1111/irv.12129/abstract
Mark I. C. Chen1,2,
Alex R. Cook1,2,3,4,
Wei Yen Lim1,
Raymond Lin5,
Lin Cui5,
Ian G. Barr6,
Anne Kelso6,
Vincent T. Chow7,
Yee Sin Leo1,2,
Jung Pu Hsu7,
Rob Shaw6,
Serene Chew2,
Joe Kwan Yap2,
Meng Chee Phoon7,
Hiromi W. L. Koh1,
Huili Zheng1,
Linda Tan1,
Vernon J. Lee1,2,*
Article first published online: 5 JUL 2013
DOI: 10.1111/irv.12129
Introduction
Previous influenza pandemics had second and on occasion third waves in many countries that were at times more severe than the initial pandemic waves.
Objective
This study aims to determine the seroepidemiology of successive waves of H1N1pdm09 infections in Singapore and the overall risks of infection.
Methods
We performed a cohort study amongst 838 adults, with blood samples provided upon recruitment and at 5 points from 2009 to 2011 and tested by haemagglutination inhibition (HI) with A/California/7/2009 (H1N1pdm09). Surveys on key demographic and clinical information were conducted at regular intervals, and associations between seroconversion and these variables were investigated.
Results
After the initial wave from June to September 2009, second and third waves occurred from November 2009 to February 2010 and April to June 2010, respectively. Seroconversion was 13?5% during the first wave and decreased to 6?2% and 6?8% in subsequent waves. Across the three waves, the elderly and those with higher starting HI titres were at lower risk of seroconversion, while those with larger households were at greater risk. Those with higher starting HI titres were also less likely to have an acute respiratory infection.
Conclusions
The second and third waves in Singapore had lower serological attack rates than the first wave. The elderly and those with higher HI titres had lower risk, while those in larger households had higher risk of seroconversion.
http://onlinelibrary.wiley.com/doi/10.1111/irv.12129/abstract