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Protective efficacy against pandemic influenza of seasonal influenza vaccination in children in Hong Kong: a randomized controlled trial.

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 2009-2010 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 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 a reduced risk of seasonal influenza B confirmed by RT-PCR, with a vaccine efficacy estimate of 66% (95% confidence interval [CI], 31%-83%). Children who received TIV also a had reduced risk of pandemic influenza A(H1N1) indicated by serology, with a 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 afterward 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 serologic response deserves further investigation. Clinical Trials Registration. NCT00792051.

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  • Authors+Show Affiliations

    ,

    School of Public Health.

    , , , , , , , , , , ,

    Source

    MeSH

    Adolescent
    Child
    Female
    Hong Kong
    Humans
    Incidence
    Influenza A Virus, H1N1 Subtype
    Influenza B virus
    Influenza Vaccines
    Influenza, Human
    Male
    Pandemics
    Placebos
    Risk Factors
    Vaccines, Inactivated

    Pub Type(s)

    Journal Article
    Randomized Controlled Trial

    Language

    eng

    PubMed ID

    22670050

    Citation

    Cowling, Benjamin J., et al. "Protective Efficacy Against Pandemic Influenza of Seasonal Influenza Vaccination in Children in Hong Kong: a Randomized Controlled Trial." Clinical Infectious Diseases : an Official Publication of the Infectious Diseases Society of America, vol. 55, no. 5, 2012, pp. 695-702.
    Cowling BJ, Ng S, Ma ES, et al. Protective efficacy against pandemic influenza of seasonal influenza vaccination in children in Hong Kong: a randomized controlled trial. Clin Infect Dis. 2012;55(5):695-702.
    Cowling, B. J., Ng, S., Ma, E. S., Fang, V. J., So, H. C., Wai, W., ... Leung, G. M. (2012). Protective efficacy against pandemic influenza of seasonal influenza vaccination in children in Hong Kong: a randomized controlled trial. Clinical Infectious Diseases : an Official Publication of the Infectious Diseases Society of America, 55(5), pp. 695-702. doi:10.1093/cid/cis518.
    Cowling BJ, et al. Protective Efficacy Against Pandemic Influenza of Seasonal Influenza Vaccination in Children in Hong Kong: a Randomized Controlled Trial. Clin Infect Dis. 2012;55(5):695-702. PubMed PMID: 22670050.
    * Article titles in AMA citation format should be in sentence-case
    TY - JOUR T1 - Protective efficacy against pandemic influenza of seasonal influenza vaccination in children in Hong Kong: a randomized controlled trial. AU - Cowling,Benjamin J, AU - Ng,Sophia, AU - Ma,Edward S K, AU - Fang,Vicky J, AU - So,Hau Chi, AU - Wai,Winnie, AU - Cheng,Calvin K Y, AU - Wong,Jessica Y, AU - Chan,Kwok-Hung, AU - Ip,Dennis K M, AU - Chiu,Susan S, AU - Peiris,J S Malik, AU - Leung,Gabriel M, Y1 - 2012/06/05/ PY - 2012/6/7/entrez PY - 2012/6/7/pubmed PY - 2013/7/9/medline SP - 695 EP - 702 JF - Clinical infectious diseases : an official publication of the Infectious Diseases Society of America JO - Clin. Infect. Dis. VL - 55 IS - 5 N2 - 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 2009-2010 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 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 a reduced risk of seasonal influenza B confirmed by RT-PCR, with a vaccine efficacy estimate of 66% (95% confidence interval [CI], 31%-83%). Children who received TIV also a had reduced risk of pandemic influenza A(H1N1) indicated by serology, with a 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 afterward 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 serologic response deserves further investigation. Clinical Trials Registration. NCT00792051. SN - 1537-6591 UR - https://www.unboundmedicine.com/medline/citation/22670050/Protective_efficacy_against_pandemic_influenza_of_seasonal_influenza_vaccination_in_children_in_Hong_Kong:_a_randomized_controlled_trial_ L2 - https://academic.oup.com/cid/article-lookup/doi/10.1093/cid/cis518 DB - PRIME DP - Unbound Medicine ER -