PLoS ONE (Jan 2021)

Prevalence of antibodies against seasonal influenza A and B viruses among older adults in rural Thailand: A cross-sectional study.

  • Nungruthai Suntronwong,
  • Preeyaporn Vichaiwattana,
  • Lakkhana Wongsrisang,
  • Sirapa Klinfueng,
  • Sumeth Korkong,
  • Thanunrat Thongmee,
  • Nasamon Wanlapakorn,
  • Yong Poovorawan

DOI
https://doi.org/10.1371/journal.pone.0256475
Journal volume & issue
Vol. 16, no. 8
p. e0256475

Abstract

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Assessing the seroprevalence of the high-risk individuals against the influenza virus is essential to evaluate the progress of vaccine implementation programs and establish influenza virus interventions. Herein, we identified the pre-existing cross-protection of the circulating seasonal influenza viruses among the older-aged population. A cross-sectional study was performed base on the 176 residual sera samples collected from older adults aged 60 to 95 years without a history of vaccination in rural Thailand in 2015. Sera antibody titers against influenza A and B viruses circulating between 2016 and 2019 were determined by hemagglutination inhibition assay. These findings indicated the low titers of pre-existing antibodies to circulating influenza subtypes and showed age-independent antibody titers among the old adults. Moderate seropositive rates (HAI ≥ 1:40) were observed in influenza A viruses (65.9%A(H3N2), 50.0% for A(H1N1) pdm09), and found comparatively lower rates in influenza B viruses (14% B/Yam2, 21% B/Yam3 and 25% B/Vic). Only 5% of individuals possessed broadly protective antibodies against both seasonal influenza A and B virus in this region. Our findings highlighted the low pre-existing antibodies to circulating influenza strains in the following season observed in older adults. The serological study will help inform policy-makers for health care planning and guide control measures concerning vaccination programs.