[Show abstract][Hide abstract] ABSTRACT: Dengue is a mosquito-transmitted virus infection that causes epidemics of febrile illness and hemorrhagic fever across the tropics and subtropics worldwide. Annual epidemics are commonly observed, but there is substantial spatiotemporal heterogeneity in intensity. A better understanding of this heterogeneity in dengue transmission could lead to improved epidemic prediction and disease control. Time series decomposition methods enable the isolation and study of temporal epidemic dynamics with a specific periodicity (e.g., annual cycles related to climatic drivers and multiannual cycles caused by dynamics in population immunity). We collected and analyzed up to 18 y of monthly dengue surveillance reports on a total of 3.5 million reported dengue cases from 273 provinces in eight countries in Southeast Asia, covering ∼10(7) km(2). We detected strong patterns of synchronous dengue transmission across the entire region, most markedly during a period of high incidence in 1997-1998, which was followed by a period of extremely low incidence in 2001-2002. This synchrony in dengue incidence coincided with elevated temperatures throughout the region in 1997-1998 and the strongest El Niño episode of the century. Multiannual dengue cycles (2-5 y) were highly coherent with the Oceanic Niño Index, and synchrony of these cycles increased with temperature. We also detected localized traveling waves of multiannual dengue epidemic cycles in Thailand, Laos, and the Philippines that were dependent on temperature. This study reveals forcing mechanisms that drive synchronization of dengue epidemics on a continental scale across Southeast Asia.
Proceedings of the National Academy of Sciences 10/2015; DOI:10.1073/pnas.1501375112 · 9.67 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Supported by GAVI Alliance, measles-rubella vaccination was introduced in Vietnam in 2014, involving a mass campaign among 1-14 year olds and routine immunization of children aged 9 months. We explore the impact on the incidence of Congenital Rubella Syndrome (CRS) during 2013-2050 of this strategy and variants involving women aged 15-35 years. We use an age and sex-structured dynamic transmission model, set up using recently-collected seroprevalence data from Central Vietnam, and also consider different levels of transmission and contact patterns. If the serological profile resembles that in Central Vietnam, the planned vaccination strategy could potentially prevent 125,000 CRS cases by 2050 in Vietnam, despite outbreaks predicted in the meantime. Targeting the initial campaign at 15-35 year old women with or without children aged 9 months-14 years led to sustained reductions in incidence, unless levels of ongoing transmission were medium-high before vaccination started. Assumptions about contact greatly influenced predictions if the initial campaign just targeted 15-35 year old women and/or levels of ongoing transmission were medium-high. Given increased interest in rubella vaccination, resulting from GAVI Alliance funding, the findings are relevant for many countries.
Human Vaccines & Immunotherapeutics 08/2015; DOI:10.1080/21645515.2015.1060380 · 2.37 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Objective The aim of this study was to compare the efficacy of cloth masks to medical masks in hospital healthcare workers (HCWs). The null hypothesis is that there is no difference between medical masks and cloth masks.
Setting 14 secondary-level/tertiary-level hospitals in Hanoi, Vietnam.
Participants 1607 hospital HCWs aged ≥18 years working full-time in selected high-risk wards.
Intervention Hospital wards were randomised to: medical masks, cloth masks or a control group (usual practice, which included mask wearing). Participants used the mask on every shift for 4 consecutive weeks.
Main outcome measure Clinical respiratory illness (CRI), influenza-like illness (ILI) and laboratory-confirmed respiratory virus infection.
Results The rates of all infection outcomes were highest in the cloth mask arm, with the rate of ILI statistically significantly higher in the cloth mask arm (relative risk (RR)=13.00, 95% CI 1.69 to 100.07) compared with the medical mask arm. Cloth masks also had significantly higher rates of ILI compared with the control arm. An analysis by mask use showed ILI (RR=6.64, 95% CI 1.45 to 28.65) and laboratory-confirmed virus (RR=1.72, 95% CI 1.01 to 2.94) were significantly higher in the cloth masks group compared with the medical masks group. Penetration of cloth masks by particles was almost 97% and medical masks 44%.
Conclusions This study is the first RCT of cloth masks, and the results caution against the use of cloth masks. This is an important finding to inform occupational health and safety. Moisture retention, reuse of cloth masks and poor filtration may result in increased risk of infection. Further research is needed to inform the widespread use of cloth masks globally. However, as a precautionary measure, cloth masks should not be recommended for HCWs, particularly in high-risk situations, and guidelines need to be updated.
Trial registration number Australian New Zealand Clinical Trials Registry: ACTRN12610000887077.
BMJ Open 04/2015; 5(4):e006577. DOI:10.1136/bmjopen-2014-006577 · 2.27 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: In this report we describe a new approach in HIV sentinel surveillance that was piloted in Viet Nam in 2009 and is currently being rolled out in all provinces. It comprises a brief behavioural questionnaire added to the HIV sentinel surveillance surveys conducted routinely among people who inject drugs, female sex workers and men who have sex with men. Timely reporting of data from this system has resulted in improvements to HIV prevention efforts for most at-risk populations.
[Show abstract][Hide abstract] ABSTRACT: Objectives
Haemagglutination inhibiting (HI) antibodies correlate with influenza vaccine protection but their association with protection induced by natural infection has received less attention and was studied here.
940 people from 270 unvaccinated households participated in active ILI surveillance spanning 3 influenza seasons. At least 494 provided paired blood samples spanning each season. Influenza infection was confirmed by RT-PCR on nose/throat swabs or serum HI assay conversion.
Pre-season homologous HI titer was associated with a significantly reduced risk of infection for H3N2 (OR 0.61, 95%CI 0.44-0.84) and B (0.65, 95%CI 0.54-0.80) strains, but not H1N1 strains, whether re-circulated (OR 0.90, 95%CI 0.71-1.15), new seasonal (OR 0.86, 95%CI 0.54-1.36) or pandemic H1N1-2009 (OR 0.77, 95%CI 0.40-1.49). The risk of seasonal and pandemic H1N1 decreased with increasing age (both p < 0.0001), and the risk of pandemic H1N1 decreased with prior seasonal H1N1 (OR 0.23, 95%CI 0.08-0.62) without inducing measurable A/California/04/2009-like titers.
While H1N1 immunity was apparent with increasing age and prior infection, the effect of pre-season HI titer was at best small, and weak for H1N1 compared to H3N2 and B. Antibodies targeting non-HI epitopes may have been more important mediators of infection-neutralizing immunity for H1N1 compared to other subtypes in this setting.
Journal of Infection 09/2014; 70(2). DOI:10.1016/j.jinf.2014.09.003 · 4.44 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: To guide control policies, it is important that the determinants of influenza transmission are fully characterized. Such assessment is complex because the risk of influenza infection is multifaceted and depends both on immunity acquired naturally or via vaccination and on the individual level of exposure to influenza in the community or in the household. Here, we analyse a large household cohort study conducted in 2007-2010 in Vietnam using innovative statistical methods to ascertain in an integrative framework the relative contribution of variables that influence the transmission of seasonal (H1N1, H3N2, B) and pandemic H1N1pdm09 influenza. Influenza infection was diagnosed by haemagglutination-inhibition (HI) antibody assay of paired serum samples. We used a Bayesian data augmentation Markov chain Monte Carlo strategy based on digraphs to reconstruct unobserved chains of transmission in households and estimate transmission parameters. The probability of transmission from an infected individual to another household member was 8% (95% CI, 6%, 10%) on average, and varied with pre-season titers, age and household size. Within households of size 3, the probability of transmission from an infected member to a child with low pre-season HI antibody titers was 27% (95% CI 21%-35%). High pre-season HI titers were protective against infection, with a reduction in the hazard of infection of 59% (95% CI, 44%-71%) and 87% (95% CI, 70%-96%) for intermediate (1∶20-1∶40) and high (≥1∶80) HI titers, respectively. Even after correcting for pre-season HI titers, adults had half the infection risk of children. Twenty six percent (95% CI: 21%, 30%) of infections may be attributed to household transmission. Our results highlight the importance of integrated analysis by influenza sub-type, age and pre-season HI titers in order to infer influenza transmission risks in and outside of the household.
[Show abstract][Hide abstract] ABSTRACT: Family plays an important role in the lives of injecting drug users (IDUs) in Vietnam. This study examined the preliminary outcomes of an intervention targeting IDUs and their family members in Vietnam. Eighty-three families, including 83 IDUs and 83 family members, were recruited from 4 communes in Phú Tḥo Province, Vietnam. The 4 communes were randomized to either an intervention condition or a standard care condition. The IDUs and their family members in the intervention condition completed 4 group sessions, with the aims to improve their mental health and family relations and to promote positive behavioral change. The intervention effect was evaluated at baseline and 3- and 6-month follow-up assessments. A significant reduction in depressive symptoms and improvement in family functioning were reported for IDUs in the intervention group compared with those in the standard care group. The family members in the intervention group reported better coping skills at 3 months, fewer depressive symptoms at 6 months, and improved family function at both 3 and 6 months compared with those in the standard care group. However, no significant intervention effect was observed for IDUs in terms of drug-using behavior. This study demonstrates the feasibility and preliminary outcomes of an intervention that simultaneously targets IDUs and their family members in Vietnam. Study findings highlight the importance of including family members and enhancing their role in drug use intervention efforts. (PsycINFO Database Record (c) 2013 APA, all rights reserved).
Psychology of Addictive Behaviors 07/2014; DOI:10.1037/a0033926 · 2.09 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Background: HIV sentinel surveillance (HSS) is conducted annually among 6 key populations in 41 provinces in Vietnam to monitor HIV prevalence. To obtain national and global indicators on risk behavior and coverage of prevention services, short behavioral questionnaire was added to HSS since 2010 among female sex workers (FSWs), injecting drug users (IDUs), and men who have sex with men (MSM). This reports data among FSWs.
Methods: Two-stage cluster sampling was applied to recruit participants based on geographic mapping where they gathering and through peer educators and local health staff. There were 5466, 7983, and 8140 FSWs sampled in 2010, 2011 and 2012. Following informed consent, respondents were interviewed with a short questionnaire about 30 questions and agreed to take a blood draw for HIV test.
Results: Overall, 7%, 3%, and 2.3% of FSWs used drugs, of whom 82%, 81%, and 70% had injected drug in the past month in 2010, 2011, and 2012 respectively. HIV prevalence among drug injecting FSWs was 29%, 22%, and 15.5% vesus HIV prevalence among overall FSWs was 4%, 2.9%, 2.7% in 2010, 2011, and 2012 respectively. The last sex condom use with client was 88.0%, 90.0%, 88.9% in 2010, 2011, and 2012. Among those injecting FSW, clean syringe needles use in the last injection was 97.5%, 92.3%, and 94.7% in 2010 and 2011. Receiving free condom in the last month was 81%, 78%, and 58.7% in 2010, 2011, and 2012. Receiving free needles among drug injecting FSWs were 46%, 58%, and 54% in 2010, 2011, and 2012. Receiving STI screening in the last 3 months was 47.3%, 32.0%, and 50.0% in 2010, 2011, and 2012. Knowing HIV test result in the last test was 52.1%, 54.3%, and 40% in 2010, 2011, and 2012.
Conclusions: HIV prevalence among injecting FSWs was much higher than among overall FSWs and closely related to drug injection. Harm reduction programs was in place but the coverage was at low level especially among injecting drug FSWs. HIV prevention efforts should increase and focus on injecting FSWs. The application of integrating a short behavioral questionnaire into HSS provides essential information for planning and evaluation.
20th International AIDS Conference, Melbourne, Australia; 07/2014
[Show abstract][Hide abstract] ABSTRACT: Background: HIV sentinel surveillance (HSS) is conducted annually among 6 key populations in 41 provinces in Viet Nam to monitor HIV prevalence trends. The HSS system began collecting risk taking behaviors among men who have sex with men (MSM) in 2010 for better understanding the HIV epidemic. The aims of this study were to determine the association between drug injection and selling sex among MSM and HIV infection in Viet Nam.
Methods: Two-stage cluster sampling was applied to recruit participants based on geographic mapping where they gathering and through peer educators and local health staff. Following informed consent, respondents were interviewed with a short questionnaire consists of 30 behavioral questions and agreed to take a blood draw for HIV test.
Results: There were 900, 800, and 800 MSM sampled in Ha Noi, An Giang, and Ho Chi Minh city (HCMC) combined during 2010, 2011 and 2012, respectively. HIV prevalence among MSM was 6.0%, 6.7%, and 6.5% in Ha Noi; 2.0%, 3.0%, and 2.0% in An Giang; 16%, 14.0%, and 7.3% in HCMC in 2010, 2011 and 2012 respectively. HIV infection was found to be associated with drug injecting behavior in HCMC in 2010 (OR: 9.5; 95% CI: 4.7-19.2) and in 2011 (OR: 5.3; 95% CI: 2.6-10.8), and in An Giang in 2011 (OR: 5.2; 95% CI: 0.9 - 30.4); and with selling sex behavior in An Giang in 2011 (OR: 8.2; 95% CI: 1.4 - 46.5) and 2012 (OR: 7.7; 95% CI: 1.1 - 56.5) respectively.
Conclusions: MSM practice multiple risk behaviors including drug injecting and selling sex. HIV prevalence was found to be associated with drug injecting and selling sex behaviors. HIV prevention efforts needs to be broadened with a focus on drug injecting and selling sex MSM. The application of integrating a short behavioral questionnaire into routine sentinel surveillance provides essential information for better understanding the HIV epidemic in Viet Nam.
20th International AIDS Conference, Melbourne, Australia; 07/2014
[Show abstract][Hide abstract] ABSTRACT: Background
Introduction of human papillomavirus (HPV) vaccine in national programs has proceeded apace since 2006, mostly in high-income countries. Recently concluded pilots of HPV vaccination in low-income countries have provided important lessons learned for these settings; however, rigorous evaluations of the feasibility of these delivery strategies that effectively reach young adolescents have been few. This paper presents results from a qualitative evaluation of a demonstration program which implemented school-based and health center–based HPV vaccinations to all girls in grade 6, or 11 years of age, for two years in four districts of Vietnam.
Using semi-structured interviews of 131 health and education staff from local, district, province, and national levels and 26 focus-group discussions with local project implementers (n = 153), we conducted a qualitative two-year evaluation to measure the impact of HPV vaccinations on the health and education systems.
HPV vaccine delivery at schools or health centers was made feasible by: a. close collaboration between the health and education sectors, b. detailed planning for implementation, c. clearly defined roles and responsibilities for project implementers, d. effective management and supervision of vaccinations during delivery, and e. engagement with community organizations for support. Both the health and education systems were temporarily challenged with the extra workload, but the disruptions were short-lived (a few days for each of three doses) and perceived as worth the longer-term benefit of cervical cancer prevention.
The learning from Vietnam has identified critical elements for successful vaccine delivery that can provide a model for other countries to consider during their planning of national rollout of HPV vaccine.
BMC Public Health 06/2014; 14(1):556. DOI:10.1186/1471-2458-14-556 · 2.26 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: This study investigated whether a large dengue epidemic that struck Hanoi in 2009 also affected a nearby semirural area. Seroconversion (dengue virus-reactive immunoglobulin G enzyme-linked immunosorbent assay) was high during 2009 compared with 2008, but neutralization assays showed that it was caused by both dengue virus and Japanese encephalitis virus infections. The findings highlight the importance of continued Japanese encephalitis virus vaccination and dengue surveillance.
The American journal of tropical medicine and hygiene 03/2014; 90(5). DOI:10.4269/ajtmh.13-0077 · 2.70 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Influenza household transmission studies are required to guide prevention strategies but most passively recruit index cases that seek healthcare. We investigated A(H1N1)pdm09 transmission in a household-based cohort during 2009.
Health-workers visited 270 households weekly, and collected swabs from influenza-like-illness cases. If A(H1N1)pdm09 was RT-PCR-confirmed, all household members had symptoms assessed and swabs collected daily for 10-15 days. Viral RNA was quantified and sequenced and serology performed on pre-pandemic sera.
Index cases were detected in 20 households containing 81 people. 98.5% lacked A(H1N1)pdm09 neutralizing antibodies in pre-pandemic sera. Eleven (18.6%, 95%CI 10.7 - 30.4%) of 59 contacts were infected. Virus genetic diversity within households was negligible and less than between households. Index and secondary cases were distributed between mothers, daughters and sons, and had similar virus-RNA shedding and symptom dynamics. Fathers were rarely infected. Five secondary cases (45%) had no apparent symptoms and three shed virus before symptoms. Secondary infection was associated with index case wet cough (OR 1.56, 95%CI 1.22 - 1.99).
In this cohort of A(H1N1)pdm09 susceptible persons, virus sequencing was capable of discriminating household from community transmission. Household transmission involved mothers and children but rarely fathers. Asymptomatic or pre-symptomatic shedding was common.
The Journal of infection 01/2014; 68(6). DOI:10.1016/j.jinf.2014.01.008 · 4.44 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The interrelationship between the well-being of injecting drug users (IDUs) and their family environment has been widely documented. However, few intervention programs have addressed the needs of both IDUs and their family members.
This study describes a randomized intervention pilot targeting 83 IDUs and 83 of their family members from four communes in Phú Thọ province, Vietnam. The IDUs and family members in the intervention condition received multiple group sessions, with the intent to improve psychological well-being and family relationships. The intervention outcomes (depressive symptoms and family relations) were evaluated at baseline, 3-month and 6-month follow-up assessments.
Depressive symptoms and family relations reported by IDUs were found to be correlated to those reported by their family members. Overall, significant intervention effects on depressive symptoms and family relations were observed for both IDUs and family members. A similar improvement pattern in family relations emerged for both the IDU and family member samples, although the intervention effect of reducing depressive symptoms was more sustainable for family members at the 6-month assessment when compared to the IDU sample.
The intervention pilot addressed challenges faced by IDUs and their family members and revealed correlated outcomes for the two groups. Findings suggest a vital need to include family members in future drug prevention and harm reduction intervention efforts.
Drug and alcohol dependence 01/2014; 134:348-354. DOI:10.1016/j.drugalcdep.2013.11.004 · 3.42 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Understanding global influenza migration and persistence is crucial for vaccine strain selection. Using 240 new human influenza A virus whole genomes collected in Vietnam during 2001-2008, we looked for persistence patterns and migratory connections between Vietnam and other countries. We found that viruses in Vietnam migrate to and from China, Hong Kong, Taiwan, Cambodia, Japan, South Korea, and the United States. We attempted to reduce geographic bias by generating phylogenies subsampled at the year and country levels. However, migration events in these phylogenies were still driven by the presence or absence of sequence data, indicating that an epidemiologic study design that controls for prevalence is required for robust migration analysis. With whole-genome data, most migration events are not detectable from the phylogeny of the hemagglutinin segment alone, although general migratory relationships between Vietnam and other countries are visible in the hemagglutinin phylogeny. It is possible that virus lineages in Vietnam persisted for >1 year.