Tweet
Clin Infect Dis. (2012) doi: 10.1093/cid/cis518 First published online: June 5, 2012
Protective efficacy against pandemic influenza of seasonal influenza vaccination in children in Hong Kong: a randomized controlled trial
Benjamin J. Cowling1,
Sophia Ng1,
Edward S. K. Ma2,
Vicky J. Fang1,
Hau Chi So1,
Winnie Wai1,
Calvin K. Y. Cheng1,
Jessica Y. Wong1,
Kwok-**** Chan3,
Dennis K. M. Ip1,
Susan S. Chiu4,
J. S. Malik Peiris1,2,*, and
Gabriel M. Leung1,*
+ Author Affiliations
1School of Public Health, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Pokfulam, Hong Kong Special Administrative Region, China
2Centre for Influenza Research, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Pokfulam, Hong Kong SAR, China
3Department of Microbiology, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Pokfulam, Hong Kong SAR, China
4Department of Pediatrics and Adolescent Medicine, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Pokfulam, Hong Kong SAR, China
Corresponding author: Dr Benjamin J Cowling, School of Public Health, The University of Hong Kong, Units 624-7, Core F, Cyberport 3, Pokfulam, Hong Kong. Tel: +852 3906 2011; Fax: +852 3520 1945; email: bcowling@hku.hk
Alternate corresponding author if the corresponding author is unavailable: Professor Gabriel M. Leung, School of Public Health, Li Ka Shing Faculty of Medicine, The University of Hong Kong, 21 Sassoon Road, Pokfulam, Hong Kong. Tel: +852 3906 2001; Fax: +852 3520 1945; email: gmleung@hku.hk
↵* Joint senior authors
Abstract
Background. The efficacy of seasonal influenza vaccination against 2009 pandemic influenza A(H1N1) remains unclear.
Methods. One child aged 6-17 years in each of 796 households was randomized to receive 2009-10 seasonal trivalent inactivated influenza vaccine (TIV) or saline placebo between August 2009 and February 2010. Households were followed up with serology, symptom diaries and collection of respiratory specimens during illnesses. The primary outcomes were influenza infection confirmed by reverse transcription polymerase chain reaction (RT-PCR) or a 4-fold or greater rise in serum antibody titer measured by hemagglutination inhibition assay.
Results. Receipt of TIV led to 8-13 fold mean geometric rises in antibody titers against seasonal A and B viruses, but only 1.5-fold mean geometric rises against the pandemic A(H1N1) virus that was not included in the vaccine. Children who received TIV had reduced risk of seasonal influenza B confirmed by RT-PCR with vaccine efficacy estimate of 66% (95% confidence interval, CI: 31%, 83%). Children who received TIV also had reduced risk of pandemic influenza A(H1N1) indicated by serology, with vaccine efficacy estimate of 47% (95% CI: 15%, 67%).
Conclusions. Seasonal TIV prevented pandemic influenza A(H1N1) and influenza B infections in children. Pandemic A(H1N1) circulated at the time of vaccination and for a short time afterwards with no substantial seasonal influenza activity during that period. The potential mechanism for seasonal TIV to provide protection, possibly short-lived, for children against pandemic A(H1N1) infection despite poor cross-reactive serological response deserves further investigation.
Protective efficacy against pandemic influenza of seasonal influenza vaccination in children in Hong Kong: a randomized controlled trial
Benjamin J. Cowling1,
Sophia Ng1,
Edward S. K. Ma2,
Vicky J. Fang1,
Hau Chi So1,
Winnie Wai1,
Calvin K. Y. Cheng1,
Jessica Y. Wong1,
Kwok-**** Chan3,
Dennis K. M. Ip1,
Susan S. Chiu4,
J. S. Malik Peiris1,2,*, and
Gabriel M. Leung1,*
+ Author Affiliations
1School of Public Health, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Pokfulam, Hong Kong Special Administrative Region, China
2Centre for Influenza Research, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Pokfulam, Hong Kong SAR, China
3Department of Microbiology, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Pokfulam, Hong Kong SAR, China
4Department of Pediatrics and Adolescent Medicine, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Pokfulam, Hong Kong SAR, China
Corresponding author: Dr Benjamin J Cowling, School of Public Health, The University of Hong Kong, Units 624-7, Core F, Cyberport 3, Pokfulam, Hong Kong. Tel: +852 3906 2011; Fax: +852 3520 1945; email: bcowling@hku.hk
Alternate corresponding author if the corresponding author is unavailable: Professor Gabriel M. Leung, School of Public Health, Li Ka Shing Faculty of Medicine, The University of Hong Kong, 21 Sassoon Road, Pokfulam, Hong Kong. Tel: +852 3906 2001; Fax: +852 3520 1945; email: gmleung@hku.hk
↵* Joint senior authors
Abstract
Background. The efficacy of seasonal influenza vaccination against 2009 pandemic influenza A(H1N1) remains unclear.
Methods. One child aged 6-17 years in each of 796 households was randomized to receive 2009-10 seasonal trivalent inactivated influenza vaccine (TIV) or saline placebo between August 2009 and February 2010. Households were followed up with serology, symptom diaries and collection of respiratory specimens during illnesses. The primary outcomes were influenza infection confirmed by reverse transcription polymerase chain reaction (RT-PCR) or a 4-fold or greater rise in serum antibody titer measured by hemagglutination inhibition assay.
Results. Receipt of TIV led to 8-13 fold mean geometric rises in antibody titers against seasonal A and B viruses, but only 1.5-fold mean geometric rises against the pandemic A(H1N1) virus that was not included in the vaccine. Children who received TIV had reduced risk of seasonal influenza B confirmed by RT-PCR with vaccine efficacy estimate of 66% (95% confidence interval, CI: 31%, 83%). Children who received TIV also had reduced risk of pandemic influenza A(H1N1) indicated by serology, with vaccine efficacy estimate of 47% (95% CI: 15%, 67%).
Conclusions. Seasonal TIV prevented pandemic influenza A(H1N1) and influenza B infections in children. Pandemic A(H1N1) circulated at the time of vaccination and for a short time afterwards with no substantial seasonal influenza activity during that period. The potential mechanism for seasonal TIV to provide protection, possibly short-lived, for children against pandemic A(H1N1) infection despite poor cross-reactive serological response deserves further investigation.
