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Population susceptibility to a variant swine-origin influenza virus A(H3N2) in Vietnam, 2011-2012.

Hoa LN, Bryant JE, Choisy M, Nguyet LA, Bao NT, Trang NH, Chuc NT, Toan TK, Saito T, Takemae N, Horby P, Wertheim H, Fox A - Epidemiol. Infect. (2015)

Bottom Line: Seroprevalence (HI ⩾ 40) was high and similar for both viruses, with 62·6% [95% confidence interval (CI) 59·4-65·7] against A/Perth/16/2009 and 54·6% (95% CI 51·4-57·8%) against A/swine/BinhDuong/03-9/2010, and no significant differences between urban and rural participants.Children aged <5 years lacked antibodies to the swine origin H3 virus despite high seroprevalence for A/Perth/16/2009.These results reveal vulnerability to infection to this contemporary swine IAV in children aged <5 years; however, cross-reactive immunity in adults would likely limit epidemic emergence potential.

View Article: PubMed Central - PubMed

Affiliation: Oxford University Clinical Research Unit and Wellcome Trust Major Overseas Programme,Vietnam.

ABSTRACT
A reassortant swine-origin A(H3N2) virus (A/swine/BinhDuong/03-9/2010) was detected through swine surveillance programmes in southern Vietnam in 2010. This virus contains haemagglutinin and neuraminidase genes from a human A(H3N2) virus circulating around 2004-2006, and the internal genes from triple-reassortant swine influenza A viruses (IAVs). To assess population susceptibility to this virus we measured haemagglutination inhibiting (HI) titres to A/swine/BinhDuong/03-9/2010 and to seasonal A/Perth/16/2009 for 947 sera collected from urban and rural Vietnamese people during 2011-2012. Seroprevalence (HI ⩾ 40) was high and similar for both viruses, with 62·6% [95% confidence interval (CI) 59·4-65·7] against A/Perth/16/2009 and 54·6% (95% CI 51·4-57·8%) against A/swine/BinhDuong/03-9/2010, and no significant differences between urban and rural participants. Children aged <5 years lacked antibodies to the swine origin H3 virus despite high seroprevalence for A/Perth/16/2009. These results reveal vulnerability to infection to this contemporary swine IAV in children aged <5 years; however, cross-reactive immunity in adults would likely limit epidemic emergence potential.

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Percentage of individuals with an HI titre ⩾40 (%) against Pe09 (blue) and Sw/VN10(red). Dots and vertical bars show the mean seroprevalences and their 95% confidenceintervals for the nine age groups defined by the thin vertical grey lines. The limits ofthese age groups were chosen so that they all contain approximately the same number ofsamples. The curves show the models of the polynomial logistic regressions, up untildegree 5 (degree 6 being non-significantly different from 0). The coloured area showsthe 95% confidence intervals of the models' predictions.
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fig02: Percentage of individuals with an HI titre ⩾40 (%) against Pe09 (blue) and Sw/VN10(red). Dots and vertical bars show the mean seroprevalences and their 95% confidenceintervals for the nine age groups defined by the thin vertical grey lines. The limits ofthese age groups were chosen so that they all contain approximately the same number ofsamples. The curves show the models of the polynomial logistic regressions, up untildegree 5 (degree 6 being non-significantly different from 0). The coloured area showsthe 95% confidence intervals of the models' predictions.

Mentions: The overall seroprevalence of titres ⩾40 against Pe09 and Sw/VN10 was 62·6% [95% confidenceinterval (CI) 59·4–65·7] and 54·6% (95% CI 51·4–57·8), respectively (Table 2). Correlation analysis of Pe09 and Sw/VN10 HI titres by Spearmancoefficient was 0·426 (rs = 82316028, P < 0·001), consistent with significantcross-reactivity to the two antigens. In children aged <5 years, only 9/70 (12·9%) wereseropositive to Sw/VN10, whereas 48/70 (68·6%) were seropositive to Pe09; these proportionswere highly significantly different (χ2 = 42·7, d.f. = 1,P < 0·001). Figure 2 showsthe polynomial logistic regressions of seroprevalence as a function of age for Pe09 andSw/VN10. Titres to Pe09 were highest in children aged <15 years, whereas highest titresto Sw/VN10 were in young adults aged 15–25 years, with very low titres observed in childrenaged <10 years, and a trough in titres for people aged 40–60 years. We propose thatthis pattern of higher reactivity in young adults reflects the influenza strains thatindividuals may have first experienced as young children, i.e. A/Wuhan/95 and A/Wyoming/03.Sex ratios were not significantly different between the two sites(χ2 = 0·0105, d.f. = 1, P = 0·9182).However, mean ages were higher in Dong Da (34·8 years) than in Ba Vi (31·2 years)(t = 2·335, d.f. = 936·809, P = 0·020). Despitethis, the age profile of HI titres was not different between the two sites, neither for Pe09(likelihood ratio test: χ2 = 0·202, d.f. = 1,P = 0·6533), nor for Sw/VN10 (likelihood ratio test:χ2 = 1·266, d.f. = 1, P = 0·2606)(Supplementary Fig. S1). Fig. 2.


Population susceptibility to a variant swine-origin influenza virus A(H3N2) in Vietnam, 2011-2012.

Hoa LN, Bryant JE, Choisy M, Nguyet LA, Bao NT, Trang NH, Chuc NT, Toan TK, Saito T, Takemae N, Horby P, Wertheim H, Fox A - Epidemiol. Infect. (2015)

Percentage of individuals with an HI titre ⩾40 (%) against Pe09 (blue) and Sw/VN10(red). Dots and vertical bars show the mean seroprevalences and their 95% confidenceintervals for the nine age groups defined by the thin vertical grey lines. The limits ofthese age groups were chosen so that they all contain approximately the same number ofsamples. The curves show the models of the polynomial logistic regressions, up untildegree 5 (degree 6 being non-significantly different from 0). The coloured area showsthe 95% confidence intervals of the models' predictions.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4595856&req=5

fig02: Percentage of individuals with an HI titre ⩾40 (%) against Pe09 (blue) and Sw/VN10(red). Dots and vertical bars show the mean seroprevalences and their 95% confidenceintervals for the nine age groups defined by the thin vertical grey lines. The limits ofthese age groups were chosen so that they all contain approximately the same number ofsamples. The curves show the models of the polynomial logistic regressions, up untildegree 5 (degree 6 being non-significantly different from 0). The coloured area showsthe 95% confidence intervals of the models' predictions.
Mentions: The overall seroprevalence of titres ⩾40 against Pe09 and Sw/VN10 was 62·6% [95% confidenceinterval (CI) 59·4–65·7] and 54·6% (95% CI 51·4–57·8), respectively (Table 2). Correlation analysis of Pe09 and Sw/VN10 HI titres by Spearmancoefficient was 0·426 (rs = 82316028, P < 0·001), consistent with significantcross-reactivity to the two antigens. In children aged <5 years, only 9/70 (12·9%) wereseropositive to Sw/VN10, whereas 48/70 (68·6%) were seropositive to Pe09; these proportionswere highly significantly different (χ2 = 42·7, d.f. = 1,P < 0·001). Figure 2 showsthe polynomial logistic regressions of seroprevalence as a function of age for Pe09 andSw/VN10. Titres to Pe09 were highest in children aged <15 years, whereas highest titresto Sw/VN10 were in young adults aged 15–25 years, with very low titres observed in childrenaged <10 years, and a trough in titres for people aged 40–60 years. We propose thatthis pattern of higher reactivity in young adults reflects the influenza strains thatindividuals may have first experienced as young children, i.e. A/Wuhan/95 and A/Wyoming/03.Sex ratios were not significantly different between the two sites(χ2 = 0·0105, d.f. = 1, P = 0·9182).However, mean ages were higher in Dong Da (34·8 years) than in Ba Vi (31·2 years)(t = 2·335, d.f. = 936·809, P = 0·020). Despitethis, the age profile of HI titres was not different between the two sites, neither for Pe09(likelihood ratio test: χ2 = 0·202, d.f. = 1,P = 0·6533), nor for Sw/VN10 (likelihood ratio test:χ2 = 1·266, d.f. = 1, P = 0·2606)(Supplementary Fig. S1). Fig. 2.

Bottom Line: Seroprevalence (HI ⩾ 40) was high and similar for both viruses, with 62·6% [95% confidence interval (CI) 59·4-65·7] against A/Perth/16/2009 and 54·6% (95% CI 51·4-57·8%) against A/swine/BinhDuong/03-9/2010, and no significant differences between urban and rural participants.Children aged <5 years lacked antibodies to the swine origin H3 virus despite high seroprevalence for A/Perth/16/2009.These results reveal vulnerability to infection to this contemporary swine IAV in children aged <5 years; however, cross-reactive immunity in adults would likely limit epidemic emergence potential.

View Article: PubMed Central - PubMed

Affiliation: Oxford University Clinical Research Unit and Wellcome Trust Major Overseas Programme,Vietnam.

ABSTRACT
A reassortant swine-origin A(H3N2) virus (A/swine/BinhDuong/03-9/2010) was detected through swine surveillance programmes in southern Vietnam in 2010. This virus contains haemagglutinin and neuraminidase genes from a human A(H3N2) virus circulating around 2004-2006, and the internal genes from triple-reassortant swine influenza A viruses (IAVs). To assess population susceptibility to this virus we measured haemagglutination inhibiting (HI) titres to A/swine/BinhDuong/03-9/2010 and to seasonal A/Perth/16/2009 for 947 sera collected from urban and rural Vietnamese people during 2011-2012. Seroprevalence (HI ⩾ 40) was high and similar for both viruses, with 62·6% [95% confidence interval (CI) 59·4-65·7] against A/Perth/16/2009 and 54·6% (95% CI 51·4-57·8%) against A/swine/BinhDuong/03-9/2010, and no significant differences between urban and rural participants. Children aged <5 years lacked antibodies to the swine origin H3 virus despite high seroprevalence for A/Perth/16/2009. These results reveal vulnerability to infection to this contemporary swine IAV in children aged <5 years; however, cross-reactive immunity in adults would likely limit epidemic emergence potential.

Show MeSH
Related in: MedlinePlus