Objective: The risk of transmission of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) from schoolchildren to their household and the protective effects of vaccination in these settings remain poorly understood. We assessed the transmission dynamics of schoolchildren with SARS-CoV-2 within their households and the protective effects of coronavirus disease (COVID-19) vaccination among household members in Viet Nam. Methods: We estimated the attack rate, vaccine effectiveness and adjusted risk ratio (aRR) of factors associated with SARS-CoV-2 transmission to household contacts of children confirmed to have COVID-19 who attended three schools in Ha Nam, Phu Tho and Thanh Hoa provinces between September and December 2021 using multivariable regression with household-level random effects. Results: This retrospective cohort study included 157 children infected with SARS-CoV-2 and their 540 household contacts. The attack rate among household contacts was 24.6% (133/540). Overall, vaccine effectiveness among household contacts was 39% (95% confidence interval [CI]: -1 to -63), higher among males than females and higher in adults aged >40 years. COVID-19 transmission was greater among female household contacts compared with males (aRR: 1.35, 95% CI: 0.94 to 1.95), although not statistically significant, and highest among those aged 19–39 years (aRR: 2.51, 95% CI: 1.50 to 4.21). Fully vaccinated household contacts had significantly lower infection risk (aRR: 0.46, 95% CI: 0.26 to 0.84). Discussion: We found substantial onward transmission of SARS-CoV-2 from schoolchildren to household members, and older people were more likely to be protected by vaccination. We recommend that schoolchildren and all household members living with schoolchildren receive at least two doses of a COVID-19 vaccine. Recognizing the role of schoolchildren in the onward transmission of COVID-19 is an important lesson learned by Viet Nam that can help not only in managing other outbreaks but also in protecting schoolchildren by predicting the progress of the outbreak and preparing for a timely response.

Objective: Human respiratory syncytial virus (RSV) is a primary cause of paediatric severe acute respiratory infection (SARI) worldwide, especially in developing countries. We investigated the genetic characteristics of RSV in northern Viet Nam to determine the prevalence and distribution of subtypes as well as the diversity and transmission patterns of genotypes. Methods: In two facilities, from January 2017 to December 2020, 1563 clinical specimens were collected from paediatric patients hospitalized with SARI and tested for RSV. Selected positive samples underwent sequencing analysis targeting the second hypervariable region of the G gene using next-generation sequencing. Results: The RSV positivity rate was 28.02% (438/1563 samples), and prevalence was highest in children aged <1 year (43.84%; 192/438). Subtype RSV-A accounted for 53.42% (234/438) of cases, RSV-B for 45.89% (201/438), and there was coinfection in 0.68% (3/438). Both subtypes cocirculated and peaked during August–September in each year of the study. Phylogenetic analysis showed that RSV-A samples belonged to the ON1 genotype, which has three subgenotypes: ON1.1, ON1.2 and ON1.3. However, we did not find the 72-nucleotide duplication in the second hypervariable region of the G gene, a characteristic of genotype ON1, in any RSV-A samples. RSV-B samples belonged to genotype BA9. Discussion: Our results provide additional molecular characterization of RSV infections in Viet Nam. Specially, our study is the first to report the absence of the 72-nucleotide duplication in the G gene of RSV-A genotype ON1 in Viet Nam, which may help in understanding the genetic evolution of RSV and be useful for vaccine development in the future.

BACKGROUND/OBJECTIVES: Although children of ethnic minority groups are experiencing a transition from a predominance of undernutrition to overnutrition, there is little evidence of a dual-malnutrition burden. Therefore, this study examined the double burden of malnutrition among school-aged ethnic minority children living in mountainous areas and its association with their diets. SUBJECTS/METHODS: A cross-sectional study was conducted from September 2019 to March 2020 in 3 mountainous areas of Northern Vietnam among 1,556 ethnic minority schoolaged children. The prevalence of under-nutrition (stunting and thinness) and over-nutrition (overweight and obesity) were measured using the WHO 2006 child growth standards (height-for-age and BMI-for-age Z-score). Nutritional practices were evaluated by the frequency of food consumption based on a 4-level scale. RESULTS: The percentage of children with stunting and thinness were 14.0% and 5.4%, respectively, while the figure for overweight/obesity was 9.4%. The factors positively associated with stunting were living in a family with more than 2 children or being Muong/ other ethnicities compared to the Tay ethnicity. Children who consumed fish/shrimps/crabs or milk weekly/daily were less likely to be undernourished compared to those who never consumed these foods. By contrast, children who never consumed foods rich in vitamin A precursors and vitamin A and fruit or consumed daily snacks/junk food were more likely to be overweight/obese. CONCLUSIONS Undernutrition remains a common issue among school-aged children and adolescents of ethnic minority groups, while over-nutrition exists simultaneously. Public health nutrition programs promoting adequate diets and positive lifestyle changes related to nutrition are essential to tackle the double burden of malnutrition among ethnic minority children.

The Omicron variant caused a surge of infections with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in Viet Nam in early 2022, signalling community transmission. We report on active whole-genome sequencing surveillance of positive SARS-CoV-2 samples collected at that time in northern Viet Nam from international arrivals and community clusters. We used an amplicon protocol developed with 14 polymerase chain reaction products and the Illumina iSeq 100 platform. Overall, 213 nasopharyngeal or throat swabs were analysed, of which 172 samples were identified with the Omicron variant. Of these, 80 samples were collected from community cases in February 2022, among which 59 samples were sublineage BA.2 and one sample was the recombinant XE variant. Our results indicated that Omicron had replaced Delta as the dominant variant in a very short period of time and that continuously conducting active whole-genome sequencing surveillance is necessary in monitoring the evolution and genomic diversity of SARS-CoV-2 in Viet Nam.

Objective: Female sex workers (FSWs) are at high risk of human papillomavirus (HPV) infections and cervical cancer due to their high number of sexual partners. The objectives of this study were to determine the prevalence of HPV and identify risk factors for high-risk HPV infection among FSWs in Hanoi and Ho Chi Minh City (HCMC), Viet Nam. Methods: A cross-sectional study was conducted in Hanoi and HCMC between December 2017 and May 2018. We surveyed and screened 699 FSWs aged ≥18 years for HPV infection and abnormal cytology. A multivariable modified Cox regression model was used to determine risk factors for high-risk HPV infection. Results The overall prevalence of any HPV, high-risk HPV and HPV-16/18 infection in the 699 FSWs was 26.3%, 17.6% and 4.0%, respectively, and were similar in both cities. Multiple infections were identified in 127 participants (69.0%).HPV-52 was the most prevalent (7%), followed by HPV-58 (6%). Abnormal cytology was detected in 91 participants (13.0%). FSWs who are divorced (adjusted prevalence ratio [aPR]: 1.96, 95% confidence interval [CI]: 1.01–3.81), widowed (aPR: 3.26, 95% CI: 1.49–7.12) or living alone (aPR: 1.85, 95% CI: 1.01–3.39) were associated with a higher prevalence of high-risk HPV infection.

Abstract Mesenchymal stem/stromal cells (MSCs) are multipotent somatic stem/progenitor cells that can be isolated from various tissues and have attracted increasing attention from the scientific community. This is due to MSCs showing great potential for incurable disease treatment, and most applications of MSCs involve tissue degeneration and treatment of immune- and inflammation-mediated diseases. Conventional MSC cultures contain fetal bovine serum (FBS), which is a common supplement for cell development but is also a risk factor for exposure to animal-derived pathogens. To avoid the risks resulting from the xenogeneic origin and animal-derived pathogens of FBS, xeno-free media have been developed and commercialized to satisfy MSC expansion demands for human clinical applications. This review summarized and provided an overview of xeno-free media that are currently used for MSC expansion. Additionally, we discussed the influences of different xeno-free media on MSC biology with particular regard to cell morphology, surface marker expression, proliferation, differentiation and immunomodulation. The xeno-free media can be serum-free and xeno-free media or media supplemented with some human-originating substances, such as human serum, human platelet lysates, human umbilical cord serum/plasma, or human plasma-derived supplements for cell culture medium. These media have capacity to maintain a spindle-shaped morphology, the expression of typical surface markers, and the capacity of multipotent differentiation and immunomodulation of MSCs. Xeno-free media showed potential for safe use for human clinical treatment. However, the influences of these xeno-free media on MSCs are various and any xeno-free medium should be examined prior to being used for MSC cultures.

Background: Vietnam is among the few countries that were successful in the fight against the first wave of coronavirus disease 2019 (COVID-19). However, subsequent domestic outbreaks of COVID-19 continue to occur. To sharp the community education program to guarantee the final success in the fight against COVID-19 in Vietnam and comparable countries, we examined the levels of COVID-19 knowledge and associated predictors among university students in Vietnam. Materials and Methods: A cross-sectional study was conducted on all students enrolling at Phenikaa University using a self-developed questionnaire consisted of 20 questions regarding COVID-19's risk factors, transmission routes, symptoms, and prevention. Results: Among 728 participants, 40.9% were male, 63.2% studied health-related majors, and 18.1% lived alone. Correct response rates ranged from 25.3% to 98.9% across 20 questions. Only 51.9% (378/728) of participants had good knowledge levels. Studying health majors (adjusted odds ratio [AOR] 0.547, 95% confidence interval [CI] 0.398 - 0.751, P <0.001), and living with the seniors (AOR 0.612, 95% CI 0.389 - 0.963, P= 0.034) or with friends (AOR 0.405, 95% CI 0.252 – 0.650, P <0.001) were negatively associated with a poor level of COVID-19 knowledge. Conclusion The proportion of university students having good knowledge levels is suboptimal. It is essential to improve the quality of COVID-19 education with a more focus on not only the preventive measures, but also the disease itself. More studies are needed to improve the level of COVID-19 knowledge among those living alone or do not study healthrelated majors.

Background: Vietnam is among the few countries that were successful in the fight against the first wave of coronavirus disease 2019 (COVID-19). However, subsequent domestic outbreaks of COVID-19 continue to occur. To sharp the community education program to guarantee the final success in the fight against COVID-19 in Vietnam and comparable countries, we examined the levels of COVID-19 knowledge and associated predictors among university students in Vietnam. Materials and Methods: A cross-sectional study was conducted on all students enrolling at Phenikaa University using a self-developed questionnaire consisted of 20 questions regarding COVID-19's risk factors, transmission routes, symptoms, and prevention. Results: Among 728 participants, 40.9% were male, 63.2% studied health-related majors, and 18.1% lived alone. Correct response rates ranged from 25.3% to 98.9% across 20 questions. Only 51.9% (378/728) of participants had good knowledge levels. Studying health majors (adjusted odds ratio [AOR] 0.547, 95% confidence interval [CI] 0.398 - 0.751, P <0.001), and living with the seniors (AOR 0.612, 95% CI 0.389 - 0.963, P= 0.034) or with friends (AOR 0.405, 95% CI 0.252 – 0.650, P <0.001) were negatively associated with a poor level of COVID-19 knowledge. Conclusion The proportion of university students having good knowledge levels is suboptimal. It is essential to improve the quality of COVID-19 education with a more focus on not only the preventive measures, but also the disease itself. More studies are needed to improve the level of COVID-19 knowledge among those living alone or do not study healthrelated majors.

Abstract Mesenchymal stem/stromal cells (MSCs) are multipotent somatic stem/progenitor cells that can be isolated from various tissues and have attracted increasing attention from the scientific community. This is due to MSCs showing great potential for incurable disease treatment, and most applications of MSCs involve tissue degeneration and treatment of immune- and inflammation-mediated diseases. Conventional MSC cultures contain fetal bovine serum (FBS), which is a common supplement for cell development but is also a risk factor for exposure to animal-derived pathogens. To avoid the risks resulting from the xenogeneic origin and animal-derived pathogens of FBS, xeno-free media have been developed and commercialized to satisfy MSC expansion demands for human clinical applications. This review summarized and provided an overview of xeno-free media that are currently used for MSC expansion. Additionally, we discussed the influences of different xeno-free media on MSC biology with particular regard to cell morphology, surface marker expression, proliferation, differentiation and immunomodulation. The xeno-free media can be serum-free and xeno-free media or media supplemented with some human-originating substances, such as human serum, human platelet lysates, human umbilical cord serum/plasma, or human plasma-derived supplements for cell culture medium. These media have capacity to maintain a spindle-shaped morphology, the expression of typical surface markers, and the capacity of multipotent differentiation and immunomodulation of MSCs. Xeno-free media showed potential for safe use for human clinical treatment. However, the influences of these xeno-free media on MSCs are various and any xeno-free medium should be examined prior to being used for MSC cultures.

Background: Coronavirus disease 2019 (COVID-19) vaccine acceptance is influenced by the trusted recommenders. This survey examined the public references, concerns, and trust in seven groups of recommenders regarding COVID-19 vaccine in Vietnam. Materials and Methods: A cross-sectional survey was conducted on 1,579 participants between April 16 and July 16, 2021. Participants’ references, concerns, and responses to vaccination recommendations made by government officials, employers, physicians, nurses, pharmacists, senior family members, and religious leaders were captured using a selfadministered questionnaire. Results: Rates of trust ranged from 18.5% to 89.1%. The highest rates were attributable to government (89.1%) and physicians (85.9%). Less than half of participants would accept the vaccines if pharmacists (45.5%), nurses (44.7%), employers (42.4%), senior family members (28.1%), and religious leaders (18.4%) recommended it. Only 37.6% of participants thought that vaccines were safe for them, while 57% were unsure. Most participants would wait and see how people respond to the vaccines before getting vaccinated (91.5%), preferred to receive the vaccines at public hospitals (88.6%), and were concerned about vaccine effectiveness (86.9%) and side effects (76.4%), while 61.8% were concerned about vaccine cost. Conclusion Focusing on the personal benefit and relying on the government, physicians, and social role models would make the vaccine advertising campaigns more effective. If annual vaccinations were needed, providing the community with affordable vaccines would be an appropriate, long-term solution to ensure vaccination coverage in low-resource countries like Vietnam. Further studies are needed to examine reasons for the public reference of vaccination centers which may help in improving their confidence in getting the vaccine, regardless of the settings.