Prevalence of seroprotection against the pandemic (H1N1) virus after the 2009 pandemic

Skowronski, Danuta M.; Salway, Travis; Janjua, Naveed Z.; Purych, Dale; Sabaiduc, Suzana; Chan, Tracy; Serres, Gaston De; Gardy, Jennifer L.; McElhaney, Janet E.; Patrick, David M.; Petric, Martin

doi:10.1503/cmaj.100910

Cited by 46 publications

(46 citation statements)

References 24 publications

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“…Our seroprevalence estimates are similar to previously published studies from Pittsburgh, PA [10] and international studies that collected sera at comparable time periods [11], [13], [15], [16], [20], [24], [36]. Consistent with other studies, school-aged children were estimated to have had the highest seroprevalance of pH1N1 antibodies [10], [11], [12], [13], [15], [24].…”

Section: Discussionsupporting

confidence: 89%

Prevalence of 2009 Pandemic Influenza A (H1N1) Virus Antibodies, Tampa Bay Florida — November–December, 2009

et al. 2011

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BackgroundIn 2009, a novel influenza virus (2009 pandemic influenza A (H1N1) virus (pH1N1)) caused significant disease in the United States. Most states, including Florida, experienced a large fall wave of disease from September through November, after which disease activity decreased substantially. We determined the prevalence of antibodies due to the pH1N1 virus in Florida after influenza activity had peaked and estimated the proportion of the population infected with pH1N1 virus during the pandemic.MethodsDuring November-December 2009, we collected leftover serum from a blood bank, a pediatric children's hospital and a pediatric outpatient clinic in Tampa Bay Florida. Serum was tested for pH1N1 virus antibodies using the hemagglutination-inhibition (HI) assay. HI titers ≥40 were considered seropositive. We adjusted seroprevalence results to account for previously established HI assay specificity and sensitivity and employed a simple statistical model to estimate the proportion of seropositivity due to pH1N1 virus infection and vaccination.ResultsDuring the study time period, the overall seroprevalence in Tampa Bay, Florida was 25%, increasing to 30% after adjusting for HI assay sensitivity and specificity. We estimated that 5.9% of the population had vaccine-induced seropositivity while 25% had seropositivity secondary to pH1N1 virus infection. The highest cumulative incidence of pH1N1 virus infection was among children aged 5–17 years (53%) and young adults aged 18–24 years (47%), while adults aged ≥50 years had the lowest cumulative incidence (11–13%) of pH1N1 virus infection.ConclusionsAfter the peak of the fall wave of the pandemic, an estimated one quarter of the Tampa Bay population had been infected with the pH1N1 virus. Consistent with epidemiologic trends observed during the pandemic, the highest burdens of disease were among school-aged children and young adults.

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Section: Discussionsupporting

confidence: 89%

Prevalence of 2009 Pandemic Influenza A (H1N1) Virus Antibodies, Tampa Bay Florida — November–December, 2009

et al. 2011

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“…We observed differences in HAI sensitivity compared to MN assay between the first and second waves that were not found in the study from British Columbia [5]. We speculate that the apparent increased sensitivity of HAI in the second wave is consistent with the hypothesis that antibodies detected by MN peaks higher but wanes faster than HAI.…”

Section: Discussionsupporting

confidence: 78%

Seroprevalence of Pandemic Influenza H1N1 in Ontario from January 2009–May 2010

et al. 2011

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BackgroundWe designed a seroprevalence study using multiple testing assays and population sources to estimate the community seroprevalence of pH1N1/09 and risk factors for infection before the outbreak was recognized and throughout the pandemic to the end of 2009/10 influenza season.MethodsResidual serum specimens from five time points (between 01/2009 and 05/2010) and samples from two time points from a prospectively recruited cohort were included. The distribution of risk factors was explored in multivariate adjusted analyses using logistic regression among the cohort. Antibody levels were measured by hemagglutination inhibition (HAI) and microneutralization (MN) assays.ResultsResidual sera from 3375 patients and 1024 prospectively recruited cohort participants were analyzed. Pre-pandemic seroprevalence ranged from 2%–12% across age groups. Overall seropositivity ranged from 10%–19% post-first wave and 32%–41% by the end of the 2009/10 influenza season. Seroprevalence and risk factors differed between MN and HAI assays, particularly in older age groups and between waves. Following the H1N1 vaccination program, higher GMT were noted among vaccinated individuals. Overall, 20–30% of the population was estimated to be infected.ConclusionsCombining population sources of sera across five time points with prospectively collected epidemiological information yielded a complete description of the evolution of pH1N1 infection.

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“…T he hemagglutination inhibition (HAI) assay is the primary method for determining quantitative antibody titers for influenza virus and is widely used both for licensure of vaccines and for seroepidemiologic studies examining protection in populations (1)(2)(3). The assay relies on the ability of the hemagglutinin protein on the surface of influenza virus to bind to sialic acids on the surface of red blood cells (RBCs) (4).…”

mentioning

confidence: 99%

Standardization of Hemagglutination Inhibition Assay for Influenza Serology Allows for High Reproducibility between Laboratories

Zacour

Ward

Brewer

et al. 2016

Clin Vaccine Immunol

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Standardization of the hemagglutination inhibition (HAI) assay for influenza serology is challenging. Poor reproducibility of HAI results from one laboratory to another is widely cited, limiting comparisons between candidate vaccines in different clinical trials and posing challenges for licensing authorities. In this study, we standardized HAI assay materials, methods, and interpretive criteria across five geographically dispersed laboratories of a multidisciplinary influenza research network and then evaluated intralaboratory and interlaboratory variations in HAI titers by repeatedly testing standardized panels of human serum samples. Duplicate precision and reproducibility from comparisons between assays within laboratories were 99.8% (99.2% to 100%) and 98.0% (93.3% to 100%), respectively. The results for 98.9% (95% to 100%) of the samples were within 2-fold of all-laboratory consensus titers, and the results for 94.3% (85% to 100%) of the samples were within 2-fold of our reference laboratory data. Low-titer samples showed the greatest variability in comparisons between assays and between sites. Classification of seroprotection (titer > 40) was accurate in 93.6% or 89.5% of cases in comparison to the consensus or reference laboratory classification, respectively. This study showed that with carefully chosen standardization processes, high reproducibility of HAI results between laboratories is indeed achievable.T he hemagglutination inhibition (HAI) assay is the primary method for determining quantitative antibody titers for influenza virus and is widely used both for licensure of vaccines and for seroepidemiologic studies examining protection in populations (1-3). The assay relies on the ability of the hemagglutinin protein on the surface of influenza virus to bind to sialic acids on the surface of red blood cells (RBCs) (4). If the patient's serum contains antibodies that block viral attachment, this interaction is inhibited. Direct comparison of results between studies has been problematic, as the reproducibility of HAI assays between laboratories has historically been poor (5-12). These studies have shown that HAI titers reported for identical specimens in different laboratories can vary as much as 80-fold or 128-fold (9, 11), with the geometric coefficient of variation (GCV) as high as 803% (5). This variability in results may relate to differences in biological reagents, protocols, and personnel training. The use of international standards (IS) may reduce interlaboratory variability (6, 11, 13), but such reagents currently exist only for influenza A H1N1 and H5N1 clade 1 viruses (14, 15). The need for standardization of HAI assays and other laboratory methods (e.g., microneutralization [MN] assays) has been highlighted as a priority of CONSISE, the Consortium for the Standardization of Influenza Seroepidemiology (16,17). CONSISE collaborators have recently published data showing that a standardized MN protocol improves the comparability of serologic results between laboratories (18); however, the conso...

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Prevalence of seroprotection against the pandemic (H1N1) virus after the 2009 pandemic

Cited by 46 publications

References 24 publications

Prevalence of 2009 Pandemic Influenza A (H1N1) Virus Antibodies, Tampa Bay Florida — November–December, 2009

Prevalence of 2009 Pandemic Influenza A (H1N1) Virus Antibodies, Tampa Bay Florida — November–December, 2009

Seroprevalence of Pandemic Influenza H1N1 in Ontario from January 2009–May 2010

Standardization of Hemagglutination Inhibition Assay for Influenza Serology Allows for High Reproducibility between Laboratories

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