Vicky J Fang

Vicky J Fang
The University of Hong Kong | HKU · School of Public Health

BSc, MPhil

About

127
Publications
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Publications

Publications (127)
Article
Full-text available
Background The protective effect of T cell-mediated immunity against influenza virus infections in natural settings remains unclear, especially in seasonal epidemics. Methods To explore the potential of such protection, we analyzed the blood samples collected longitudinally in a community-based study and covered the first wave of pandemic H1N1 (pH...
Article
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Influenza virus infections can lead to a number of secondary complications, including sepsis. We applied linear regression models to mortality and hospital admission data coded for septicaemia from 1998 to 2019 in Hong Kong, and estimated that septicaemia was associated with an annual average excess mortality rate of 0.23 (95% CI 0.04–0.40) per 100...
Article
We explored the potential for a biphasic pattern in waning of antibody titers after influenza vaccination. We collected blood samples in a randomized controlled trial of influenza vaccination in children, and tested them with hemagglutination inhibition (HAI) assays for influenza A(H3N2) and influenza B/Victoria lineage. Using piecewise log-linear...
Article
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For >70 years, a 4-fold or greater rise in antibody titer has been used to confirm influenza virus infections in paired sera, despite recognition that this heuristic can lack sensitivity. Here we analyze with a novel Bayesian model a large cohort of 2353 individuals followed for up to 5 years in Hong Kong to characterize influenza antibody dynamics...
Preprint
For >70 years, a 4-fold or greater rise in antibody titer has been used to confirm influenza virus infections in paired sera, despite recognition that this heuristic can lack sensitivity. Here we analyze with a novel Bayesian model a large cohort of 2,353 individuals followed for up to 5 years in Hong Kong to characterize influenza antibody dynamic...
Article
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The vaccine efficacy of standard-dose seasonal inactivated influenza vaccines (S-IIV) can be improved by the use of vaccines with higher antigen content or adjuvants. We conducted a randomized controlled trial in older adults to compare cellular and antibody responses of S-IIV versus enhanced vaccines (eIIV): MF59-adjuvanted (A-eIIV), high-dose (H-...
Article
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Background Brief assessments of functional status for community-dwelling older adults are needed given expanded interest in the measurement of functional decline. Methods As part of a 2015 prospective cohort study of older adults aged 60–89 years in Jiangsu Province, China, 1506 participants were randomly assigned to two groups; each group was adm...
Article
Background: We analysed data from a randomized controlled trial on the reactogenicity of three enhanced influenza vaccines compared to standard-dose inactivated influenza vaccine. Methods: We enrolled community-dwelling older adults in Hong Kong, and randomly allocated them to receive 2017/18 northern hemisphere formulations of: standard-dose va...
Article
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Objectives: Enhanced inactivated influenza vaccines (eIIV) aim to increase immunogenicity and protection compared with the widely used standard IIV (S-IIV). Methods: We tested four vaccines in parallel, FluZone high dose, FluBlok and FluAd versus S-IIV in a randomised controlled trial of older adults and in a mouse infection model to assess immu...
Article
Background: Human influenza virus infections cause a considerable burden of morbidity and mortality worldwide each year. Understanding regional influenza-associated outpatient burden is crucial for formulating control strategies against influenza viruses. Methods: We extracted the national sentinel surveillance data on outpatient visits due to i...
Article
Background Enhanced influenza vaccines may improve protection for older adults, but comparative immunogenicity data are limited. Our objective was to examine immune responses to enhanced influenza vaccines, compared to standard-dose vaccines, in community-dwelling older adults. Methods Community-dwelling older adults aged 65–82 years in Hong Kong...
Article
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Objectives: Influenza causes a spectrum of disease from asymptomatic infection to fatal outcome, and pre-existing immunity can alter susceptibility and disease severity. In a household transmission study, we recruited outpatients with confirmed influenza virus infection and prospectively identified secondary infections in their household contacts,...
Article
Background: Studies that correlate maternal antibodies with protection from influenza A or B virus infection in young infants in areas with prolonged influenza circulation are lacking. Methods: We conducted a prospective, observational study to evaluate the effects of maternal-transferred antibodies against influenza A and B viruses against labo...
Article
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Background The estimation of influenza-associated excess mortality in countries can help to improve estimates of the global mortality burden attributable to influenza virus infections. We did a study to estimate the influenza-associated excess respiratory mortality in mainland China for the 2010–11 through 2014–15 seasons. Methods We obtained prov...
Article
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Background The estimation of influenza-associated excess mortality in countries can help to improve estimates of the global mortality burden attributable to influenza virus infections. We did a study to estimate the influenza-associated excess respiratory mortality in mainland China for the 2010–11 through 2014–15 seasons. Methods We obtained prov...
Article
Background: Immune responses to influenza vaccination can be weaker in older adults than in other age groups. We hypothesized that antibody responses would be particularly weak among repeat vaccinees when the current and prior season vaccine components are the same. Methods: An observational study was conducted among 827 older adults aged ≥75 ye...
Article
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Influenza A viruses evolve rapidly to escape host immunity, causing reinfection. The form and duration of protection after each influenza virus infection are poorly understood. We quantify the dynamics of protective immunity by fitting individual-level mechanistic models to longitudinal serology from children and adults. We find that most protectio...
Article
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Haemagglutination inhibition (HAI) antibody titres are a correlate of protection for influenza virus infection, but several studies have also demonstrated the protective role of anti-neuraminidase (anti-NA) antibodies. However, there is limited data on anti-NA antibody responses in naturally occurring human influenza. We investigated anti-NA antibo...
Article
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Vaccination is an important intervention to prevent influenza virus infection, but indirect protection of household members of vaccinees is not fully known. Here, we analyze a cluster household randomized controlled trial, with one child in each household randomized to receive influenza vaccine or placebo, for an influenza B epidemic in Hong Kong....
Article
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Statistical models are commonly employed in the estimation of influenza-associated excess mortality that, due to various reasons, is often underestimated by laboratory-confirmed influenza deaths reported by healthcare facilities. However, methodology for timely and reliable estimation of that impact remains limited because of the delay in mortality...
Article
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In winter 2018, schools in Hong Kong were closed 1 week before the scheduled Chinese New Year holiday to mitigate an influenza B virus epidemic. The intervention occurred after the epidemic peak and reduced overall incidence by ≈4.2%. School-based vaccination programs should be implemented to more effectively reduce influenza illnesses.
Article
Background: The hemagglutination inhibition (HAI) assay is an established correlate of protection for the inactivated influenza vaccine, but the proportion of vaccine-induced protection that is mediated by the post-vaccination HAI titer has not been assessed. Methods: We used data from a randomized placebo-controlled trial of a split-virion inac...
Article
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We used national sentinel surveillance data in China for 2005-2016 to examine the lineage-specific epidemiology of influenza B. Influenza B viruses circulated every year with relatively lower activity than influenza A. B/Yamagata was more frequently detected in adults than in children.
Data
National influenza sentinel surveillance, China; laboratory methods for determining influenza B lineages; proportion of clinics involved in national influenza sentinel surveillance; distribution of specimens from surveillance hospitals and proportions of network laboratories using various testing methods; national influenza virus activity by virus...
Preprint
Full-text available
Influenza A viruses evolve rapidly to escape host immunity, such that individuals may be infected multiple times with the same subtype. The form and duration of protective immunity after each influenza infection are poorly understood. Here, we quantify the dynamics of protective immunity against influenza A virus infections by fitting individual-le...
Article
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Background Many serologic studies were done during and after the 2009 influenza pandemic, to estimate the cumulative incidence of influenza A(H1N1)pdm09 virus infections, but there are few comparative estimates of the incidence of influenza A(H3N2) virus infections during epidemics. Methods We conducted a longitudinal serologic study in Hong Kong....
Article
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A novel avian-origin influenza A(H7N9) virus emerged in China in March 2013 and by 27 September 2017 a total of 1533 laboratory-confirmed cases have been reported. Occurrences of animal-to-human and human-to-human transmission have been previously identified, and the force of human-to-human transmission is an important component of risk assessment....
Article
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Influenza viruses may cause severe human infections leading to hospitalization or death. Linear regression models were fitted to population-based data on hospitalizations and deaths. Surveillance data on influenza virus activity permitted inference on influenza-associated hospitalizations and deaths. The ratios of these estimates were used as a pot...
Article
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Background: Many health authorities recommend influenza vaccination of older adults to reduce disease burden. We hypothesized that in tropical and subtropical areas with more prolonged influenza seasons, twice-annual influenza vaccination might provide older adults with improved immunity against influenza. Methods: In 2014/15, Hong Kong experien...
Article
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Background: School-aged children have the highest incidence of respiratory virus infections each year, and transmission of respiratory viruses such as influenza virus can be a major concern in school settings. School absenteeism data have been employed as a component of influenza surveillance systems in some locations. Data timeliness and system a...
Article
p>BACKGROUND: The avian influenza A H7N9 virus has caused infections in human beings in China since 2013. A large epidemic in 2016-17 prompted concerns that the epidemiology of the virus might have changed, increasing the threat of a pandemic. We aimed to describe the epidemiological characteristics, clinical severity, and time-to-event distributio...
Article
Background: Since 2014, 17 human cases of infection with the newly emerged highly pathogenic avian influenza A(H5N6) virus have been identified in China to date. The epidemiologic characteristics of laboratory-confirmed A(H5N6) cases were compared to A(H5N1) and A(H7N9) cases in mainland China. Methods: Data on laboratory-confirmed H5N6, H5N1, a...
Article
Background: Influenza B virus has been perceived to cause less disease burden and milder disease when compared to influenza A, but recent studies suggest influenza B does have a significant impact. We aimed to estimate the burden of influenza B virus infections on hospitalizations in Hong Kong, in the context of virus lineage changes over time. M...
Article
Background: Influenza virus infections are associated with a wide spectrum of disease. However, few studies have investigated in detail the epidemiology and virology of asymptomatic and mild illness with influenza virus infections. Methods: In a community-based study in Hong Kong from 2008 to 2014, we followed up initially healthy individuals wh...
Article
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Middle East Respiratory syndrome (MERS) first emerged in Saudi Arabia in 2012 and remains a global health concern. The objective of this study was to compare the clinical features and risk factors for adverse outcome in patients with RT-PCR confirmed MERS and in those with acute respiratory disease who were MERS-CoV negative, presenting to the King...
Article
Background: Some studies have hypothesized that vitamin D may have a role to play in protection against influenza virus infections and illnesses, and that seasonal fluctuation in serum 25-hydroxyvitamin D [25(OH)D] may affect seasonal patterns of influenza virus infections. Objective: We aimed to investigate whether serum 25(OH)D concentrations...
Article
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The incubation period is an important epidemiologic distribution, it is often incorporated in case definitions, used to determine appropriate quarantine periods, and is an input to mathematical modeling studies. Middle East Respiratory Syndrome coronavirus (MERS) is an emerging infectious disease in the Arabian Peninsula. There was a large outbreak...
Article
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Since March 2013, a novel influenza A(H7N9) virus has caused 3 epidemic waves of human infection in mainland China. We analyzed data from patients with laboratory-confirmed influenza A(H7N9) virus infection to estimate the risks for severe outcomes after hospitalization across the 3 waves. We found that hospitalized patients with confirmed infectio...
Data
Table shows the number of influenza A(H7N9) cases, deaths, intensive-care-unit admissions, and those on mechanical ventilation reported during epidemic waves in mainland China, 2013–2015, and also a definition of the term residence as used in the study.
Article
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Background: Identifying individual correlates of infectivity of influenza virus is important for disease control and prevention. Viral shedding is used as a proxy measure of infectivity in many studies. However, the evidence for this is limited. Methods: In a detailed study of influenza virus transmission within households in 2008-12, we recruit...
Data
Observed viral shedding of index cases with low, medium or high level of viral shedding at symptom onset. (DOCX)
Data
Factors affecting influenza susceptibility and infectivity in the household transmission model included household with multiple index cases. (DOCX)
Data
Characteristics of index cases without or with at least one household contact with symptoms. (DOCX)
Article
Most influenza virus infections are associated with mild disease. One approach to estimate the occurrence of influenza virus infections in individuals is via repeated measurement of humoral antibody titres. We used baseline and convalescent antibody titres measured by haemagglutination inhibition (HI) and viral neutralization (VN) assays against in...
Article
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Background: In early 2013, a novel avian-origin influenza A(H7N9) virus emerged in China, and has caused sporadic human infections. The incubation period is the delay from infection until onset of symptoms, and varies from person to person. Few previous studies have examined whether the duration of the incubation period correlates with subsequent...
Article
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During the early stage of an epidemic, timely and reliable estimation of the severity of infections are important for predicting the impact that the influenza viruses will have in the population. We obtained age-specific deaths and hospitalizations for patients with laboratory-confirmed H1N1pdm09 infections from June 2009 to December 2009 in Hong K...
Article
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Background: Although the pattern of viral shedding over time has been documented in volunteer challenge studies, understanding on the relationship between clinical symptomatology and viral shedding in naturally acquired influenza infections in human remains limited. Methods: In a community-based study in Hong Kong from 2008-2014, we followed up...
Article
Background: In influenza epidemiology, analysis of paired sera collected from people before and after influenza seasons has been used for decades to study the cumulative incidence of influenza virus infections in populations. However, interpretation becomes challenging when sera are collected after the start or before the end of an epidemic, and d...
Article
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Background: Correlations between hemagglutination-inhibition titers (hereafter 'titers') and protection against infection have been identified in historical studies. However, limited information is available about the dynamics of how titer influences protection. Methods: Titers were measured in randomized, placebo-controlled vaccine trials in Ho...
Article
A novel avian influenza virus, influenza A(H7N9), emerged in China in early 2013 and caused severe disease in humans, with infections occurring most frequently after recent exposure to live poultry. The distribution of A(H7N9) incubation periods is of interest to epidemiologists and public health officials, but estimation of the distribution is com...
Article
Influenza B viruses split into 2 distinct lineages in the early 1980s, commonly named the Victoria and Yamagata lineages. There are few data on the comparative epidemiology of Victoria- and Yamagata-lineage viruses. In 2007–2011, we enrolled 75 and 34 households containing index patients with acute respiratory illness who tested positive for Yamaga...
Article
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Background: The novel influenza A(H7N9) virus has caused 2013 spring and 2013-2014 winter waves of human infections since its first emergence in China in March 2013. Exposure to live poultry is a risk factor for H7N9 infection. Public psychobehavioral responses often change during progression of an epidemic. Methods: We conducted population-base...
Article
South Korea is experiencing the largest outbreak of Middle East respiratory syndrome coronavirus infections outside the Arabian Peninsula, with 166 laboratory- confirmed cases, including 24 deaths up to 19 June 2015. We estimated that the mean incubation period was 6.7 days and the mean serial interval 12.6 days. We found it unlikely that infectiou...
Article
Few previous studies have investigated the association between the severity of an infectious disease and the length of incubation period. We estimated the association between the length of the incubation period and the severity of infection with the severe acute respiratory syndrome coronavirus, using data from the epidemic in 2003 in Hong Kong. We...
Article
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Vitamin D plays an important role in skeletal health throughout life. Some studies have hypothesised that vitamin D may reduce the risk of other diseases. Our study aimed to estimate age-specific and sex-specific serum 25-hydroxyvitamin D (25(OH)D) status and to identify the determinants of serum 25(OH)D status in Hong Kong, a subtropical city in s...
Article
Respiratory viruses cause acute respiratory diseases with a broad and overlapping spectrum of symptoms. We examined the clinical symptoms and explored the patterns of various respiratory viral infections in children in Hong Kong. Among 2090 specimens collected from outpatient care (2007∼ 2010), 1343 (64.3%) were positive for any virus by the xTAG a...