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Effectiveness of the 2010 and 2011 Southern Hemisphere trivalent inactivated influenza vaccines against hospitalization with influenza-associated acute respiratory infection among Thai adults aged ≥ 50 years.

Abstract

BACKGROUND

Inactivated influenza vaccine (IIV) effectiveness has been evaluated among older adults in high-income countries, but data on IIV effectiveness in low- and middle-income countries remain sparse. We conducted a test-negative case-control analysis to estimate 2010 and 2011 trivalent IIV effectiveness against hospitalization with influenza-associated acute respiratory infection (ARI) among persons aged ≥ 50 years in rural Thailand.

METHODS

During 2010-2011, active surveillance for ARI hospitalization was conducted in two provinces; patients were tested for influenza viruses by real-time RT-PCR. Vaccination status was obtained from vaccine registries. Case and control patients were patients with nasopharyngeal swabs positive and negative for influenza viruses, respectively. Vaccine effectiveness (VE) was estimated for the 6 months after vaccination began. Logistic regression was used to evaluate the association between case status and vaccination while adjusting for age, province, medical conditions, and time.

RESULTS

During 2010-2011, there were 1545 patients with ARI, of whom 279 (18%) were influenza-positive case patients and 1266 (82%) were influenza-negative control patients. Of the 279 case patients, 247 (89%) had influenza A and 32 (11%) had influenza B. Fourteen of 279 (5%) case patients and 108 of 1266 (9%) control patients were vaccinated against influenza. The unadjusted IIV effectiveness against hospitalization with influenza-associated ARI was 43% (95% CI: 0-68%); adjusted VE was 47% (95% CI: 5-71%).

CONCLUSION

The 2010 and 2011 IIVs were moderately effective against hospitalization with influenza-associated ARI among Thais aged ≥ 50 years, but IIV coverage was low. Additional efforts are warranted in Thailand to improve IIV uptake in this target group.

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  • Authors+Show Affiliations

    ,

    Influenza Division, Centers for Disease Control and Prevention, Atlanta, GA, USA.

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    Source

    MeSH

    Aged
    Aged, 80 and over
    Animals
    Case-Control Studies
    Female
    Hospitalization
    Humans
    Influenza Vaccines
    Influenza, Human
    Male
    Middle Aged
    Orthomyxoviridae
    Real-Time Polymerase Chain Reaction
    Reverse Transcriptase Polymerase Chain Reaction
    Rural Population
    Thailand
    Treatment Outcome

    Pub Type(s)

    Journal Article

    Language

    eng

    PubMed ID

    24490684

    Citation

    Dawood, Fatimah S., et al. "Effectiveness of the 2010 and 2011 Southern Hemisphere Trivalent Inactivated Influenza Vaccines Against Hospitalization With Influenza-associated Acute Respiratory Infection Among Thai Adults Aged ≥ 50 Years." Influenza and Other Respiratory Viruses, vol. 8, no. 4, 2014, pp. 463-8.
    Dawood FS, Prapasiri P, Areerat P, et al. Effectiveness of the 2010 and 2011 Southern Hemisphere trivalent inactivated influenza vaccines against hospitalization with influenza-associated acute respiratory infection among Thai adults aged ≥ 50 years. Influenza Other Respir Viruses. 2014;8(4):463-8.
    Dawood, F. S., Prapasiri, P., Areerat, P., Ruayajin, A., Chittaganpitch, M., Muangchana, C., ... Olsen, S. J. (2014). Effectiveness of the 2010 and 2011 Southern Hemisphere trivalent inactivated influenza vaccines against hospitalization with influenza-associated acute respiratory infection among Thai adults aged ≥ 50 years. Influenza and Other Respiratory Viruses, 8(4), pp. 463-8. doi:10.1111/irv.12233.
    Dawood FS, et al. Effectiveness of the 2010 and 2011 Southern Hemisphere Trivalent Inactivated Influenza Vaccines Against Hospitalization With Influenza-associated Acute Respiratory Infection Among Thai Adults Aged ≥ 50 Years. Influenza Other Respir Viruses. 2014;8(4):463-8. PubMed PMID: 24490684.
    * Article titles in AMA citation format should be in sentence-case
    TY - JOUR T1 - Effectiveness of the 2010 and 2011 Southern Hemisphere trivalent inactivated influenza vaccines against hospitalization with influenza-associated acute respiratory infection among Thai adults aged ≥ 50 years. AU - Dawood,Fatimah S, AU - Prapasiri,Prabda, AU - Areerat,Peera, AU - Ruayajin,Asadang, AU - Chittaganpitch,Malinee, AU - Muangchana,Charung, AU - Baggett,Henry C, AU - Olsen,Sonja J, Y1 - 2014/02/03/ PY - 2013/12/02/accepted PY - 2014/2/5/entrez PY - 2014/2/5/pubmed PY - 2015/1/27/medline KW - Case-control studies KW - elderly KW - flu vaccines KW - hospitalization KW - influenza vaccine SP - 463 EP - 8 JF - Influenza and other respiratory viruses JO - Influenza Other Respir Viruses VL - 8 IS - 4 N2 - BACKGROUND: Inactivated influenza vaccine (IIV) effectiveness has been evaluated among older adults in high-income countries, but data on IIV effectiveness in low- and middle-income countries remain sparse. We conducted a test-negative case-control analysis to estimate 2010 and 2011 trivalent IIV effectiveness against hospitalization with influenza-associated acute respiratory infection (ARI) among persons aged ≥ 50 years in rural Thailand. METHODS: During 2010-2011, active surveillance for ARI hospitalization was conducted in two provinces; patients were tested for influenza viruses by real-time RT-PCR. Vaccination status was obtained from vaccine registries. Case and control patients were patients with nasopharyngeal swabs positive and negative for influenza viruses, respectively. Vaccine effectiveness (VE) was estimated for the 6 months after vaccination began. Logistic regression was used to evaluate the association between case status and vaccination while adjusting for age, province, medical conditions, and time. RESULTS: During 2010-2011, there were 1545 patients with ARI, of whom 279 (18%) were influenza-positive case patients and 1266 (82%) were influenza-negative control patients. Of the 279 case patients, 247 (89%) had influenza A and 32 (11%) had influenza B. Fourteen of 279 (5%) case patients and 108 of 1266 (9%) control patients were vaccinated against influenza. The unadjusted IIV effectiveness against hospitalization with influenza-associated ARI was 43% (95% CI: 0-68%); adjusted VE was 47% (95% CI: 5-71%). CONCLUSION: The 2010 and 2011 IIVs were moderately effective against hospitalization with influenza-associated ARI among Thais aged ≥ 50 years, but IIV coverage was low. Additional efforts are warranted in Thailand to improve IIV uptake in this target group. SN - 1750-2659 UR - https://www.unboundmedicine.com/medline/citation/24490684/Effectiveness_of_the_2010_and_2011_Southern_Hemisphere_trivalent_inactivated_influenza_vaccines_against_hospitalization_with_influenza_associated_acute_respiratory_infection_among_Thai_adults_aged_≥_50_years_ L2 - https://doi.org/10.1111/irv.12233 DB - PRIME DP - Unbound Medicine ER -